234 10 13190 https://digitalcollections.lakeheadu.ca/files/original/319737665e4e4e9fe870d76d13c8daee.pdf 497c207e45c1c9701e58ec0f9bc66e67 PDF Text Text Institute on Lake Superior Geology GEOLOGICAL EXPLORATION A collection of twelve papers and three panel discussions presented at the Institute on Lake Superior Geology, Houghton, Michigan, 1956 The Michigan College of Mining and Technology Press �2 (5100x6600x16M tiff) �Copyright 1957 by The Michgan College of Mining and Technology Noughton, Michigan Lithoprinted in U.S.A. EDWARDS BROTHERS, INC. Ann Arbor, Michigan �A Publication of Papers Delivered at the Institute on Lake Superior Geolopy Houghton, May l!-12, 1956 on Geological Exploration Steering Committee A. K. Sneigrove, Chairman; Michigan College of Mining & Technology L. 0. Bacon, Michigan College of Mining & Technology W. Been, Michigan College of Mining & Technology B. H. Boyurrt, Cleveland—Cliffs Iron Company A. T. Broderick, Inland Steel Company W. L. Daoust, Michigan State Geologist J. P. Dobell, Michigan College of Mining & Technology, Treasurer R. W. Drier, Michigan College of Mining & Technology C. 1E. Dutton, U. S. Geological Survey G. A. Hoffman, Jones & Laughlin Ore Company V. E, Kral, Ford Motor Company W. A. Longacre, Michigan College of Mining & Technology A. N. Macintosh, Michigan College of Mining & Technology N. H. Manderfield, Michigan College of Mining & Technology J. M. Neilson, Michigan College of Mining & Technology J. R. Rand, White Pine Copper Company i. Royce, Pickands Mather & Company L. C. Smith, North Range Mining Company K. Spiroff, Michigan College of Mining & Technology M. E. Volin, Michigan College of Mining & lechrtology K. L. Weir, U. S. Geological Survey Cosponsors Michigan College of Mining and Technology Geological Survey of Michigan Exploration Subsection, Upper Peninsula Section) American Institute of Mining, Metallurgical and Petroleum Engineers 'UI �Contents Regional Structural Setting of the Michigan Native Copper District by Walter S. White, U.S. Geological Survey Copper Mineralization at the White Pine Mine, Ontonagon County, Michigan by John R. Rand, Consulting Geologist, White Pine Copper Company Comments on Preceding Papers Page 3 17 18 by T, M. Broderick, Calumet, Michigan Geology and Mineral Deposits of the Man itouwadge Lake Area, Ontario by E. G. Pye, Ontario Department of Mines The Blind River, Ontario, Uranium Area by S. M. Roscoe, Geological Survey of Canada Magnetic Prospecting for Iron Ores by W. George Wahl, Consulting Geologist, Willowdale, Ontario Relationship of Gravity to Geologic Structure in Michigan's Upper Peninsula by 1. 0. Bacon, Michigan College of Mining and Technology Geological Factors Affecting Beneficiation of Lake Superior Iron Ores by M. E. Volin, Bureau of Mineral Research, Michigan College of Mining and Technology Geological Characteristics of Michigan Iron Ores Affecting Beneficiation (Panel) by Alan T. Broderick, Inland Steel Company The Relationship of Diagenesis, Metamorphism and Secondary Oxidation to the Concentrating Characteristics of the Negaunee Iron Formation of the 26 40 49 54 59 60 63 Marquette Range (Panel) by G. J. Anderson and Tsu Ming Han, The Cleveland—Cliffs Iron Company The Nature and Beneficiating Properties of Michipicoten Siderites (Panel) Part I. Distribution and Nature by A. M. Goodwin, Algoma Ore Properties, Limited Part II. Beneficiating Properties by D. R. Dorrance, Aigoma Ore Properties, Limited Distribution of Trace Elements in Soil Fractions by D. H. Yardley, University of Minnesota Trends in Geochemical Exploration by H. E. Hawkes, Massachusetts Institute of Technology Applied Photogeology by W. Warren Longley, Consultant, Aero Service Corporation, Philadelphia, Pennsylvania Modern Techniques of Photogeology and Photogrammetry in Natural Resource Development by John C. Bayless, Abrams Aerial Survey Corporation, Lansing, Michigan 70 74 76 86 94 102 �FOREWORD This publication is the record of the Institute on Lake Superior Geology which was held at the Michigan College of Mining and Technology, Houghton, Michigan, on May II and 12, 1956. The theme of the Institute was Geological Exploration and its purpose was to review exploration developments on both sides of the international border in both practice and theory. The Institute was made possible through the full cooperation of governmental agencies, the mineral industries, the institutions of higher education represented, and by private consultants who gave freely of their rich background of experience. All of the speakers were specially invited as leaders in their fields. The Institute is particularly indebted to the United States Geological Survey, the United States Atomic Energy Commission, the Geological Survey of Canada and the Ontario Department of Mines. The considerable task of transcribing the tape—recordings of several of the papers and all of the discussions was efficiently performed by Mrs. Marian 1. Hoyt, Secretary of the Department of Geology and Geological Engineering, Michigan College of Mining and Technology. These discussions are reported in semi—colloquial style. The three cosponsors, The Geological Survey of Michigan, the Exploration Subsection of the Upper Peninsula of Michigan Section of the American Institute of Mining, Metallurgical and Petroleum Engineers, and the Michigan College of Mining and Technology, join in thanking most cordially the participants and are glad to share with them the satisfaction of service to the profession of Geology. A. K. Snelgrove ��REGIONAL STRUCTURAL SETTING OF THE MICHIGAN NATIVE COPPER DISTRICT* by Walter S. White Introduction The native copper deposits of Michigan ore in mafic lovas and conglomerate beds of middle Keweenawan age. These rocks crop out all around the Lake Superior basin (Fig. I). Although Fig. — Generolized geologic mop of the Loke Superior region. Modified ofter Leith, Lund, and Leith (1935, pl. I) I *Publ;cation authorized by the Director, U.S. Geological Survey. 3 �the lavas, in particular, contain small amounts of copper almost everywhere, over 97 percent of the native copper mined from the region has come from a single area less than 30 miles long and only 2 or 3 miles wide — about I percent of the total area in which lavas of middle Keweenawan age form the bedrock. This paper proposes a possible explanation for this apparent concentration of economic deposits. The explanation is admittedly a very great oversimplification of a complex problem, but though we may not know all the reasons for localization of an ore deposit or district, we have useful if not infallible, tools for exploration when we know one or more of the most fundamental reasons. If the explanation proposed here is a correct one, it suggests one measure of the relative promise of various parts of the Lake Superior basin, and may even have application in other areas of the world with thick accumulations of basaltic lava. The general characteristics of the native copper deposits of Michigan have been described many times, and need not be reviewed in detail here. The most complete description is by Butler and others (1929), and briefer summaries can be found in Lindgren (1933, p. 517—527), Bateman (1950, p. 496—498), and other textbooks. The copper district (Fig. 2) lies on the south flank of the MILES GENERALIZED GEOLOGIC MAP OF MICHIGAN COPPER DISTRICT SHOWING PRINCIPAL MINES IN PLAN 0 Fig. 2 - Middle Keweenawan lavas (unshaded) dip 25 0 — 70 NW. Mines, shown by dark shading, are numbered as follows: I. Baltic amygdaloid mines (Champion mine at south- west end); 2. Atlantic mine; 3. Isle Royale mine; 4. Quincy mine; 5. Calumet & Hecla mine; 6. Osceola amygdaloid mine (workings partly beneath Calumet & Hecla mine); 7. Kearsarge amygdalod mines. The village of Houghton is just north of the Isle Royale mine and the village of Calumet is underlain by workings of the Calumet & Hecla mine. Keweenawan basin, and the stratified rocks of the district dip northwest toward the center of this The lavas of middle Keweenawan age (unshaded in Fig. 2) have dips that range from 25° to 70° NW., with the steeper dips prevailing near the Keweenaw fault. The sandstones of late Keweenawan age dip more gently. The Keweenaw fault is a reverse fault that separates the lavas of middle Keweenawan age From the more or less flatlying Jacobsvilte sandstone, of upper Keweenawar or Cambrian age. basin. Native copper occurs as fillings in the amygdules and interstices of the Fragmental tops of individual lava flows. This copper is associated with a number of other secondary filling minerals, principally chlorite, calcite, prehnite, epidote, and quartz, with subordinate red potash feldspar and zeolites. Some copper is found as interstitial Fillings and replacements in rhyolite conglomerate beds lying between a few of the lava flows; nearly 40 percent oF the copper from the district came from the single major conglomerate ore body discovered to date. 4 �Individual ore deposits are large in terms of area (Fig. 2). The amygdaloidal top of the Kearsarge flow has been continuously mined for six miles along the strike, and for nearly a mile down the dip, on the average. The ore body in the Calumet and Hecla conglomerate at Calumet covers an area of more than three square miles in the plane of the conglomerate bed. The thickness of the individual flow tops and conglomerate beds in these and other ore bodies ranges, at most places, from about 5 to 25 feet. The average grade of ore that has been mined from the lavas is probably a little less than 1 percent, whereas that from the Calumet and Hecla conglomerate averaged between 2 and 3 percent. The origin of the copper deposits has been debated for many years, as befits a district that has been prominent in the literature of mining and geology for more than a century. Some features of their origin, however, now seem well established. The copper is definitely epigenetic where it is present in sufficient abundance to make ore deposits. There is also good presumptive evidence that the copper moved up rather than down the dip of the amygdaloidal layers and conglomerate beds to reach its resting place in the present ore deposits. Detailed evidence on these important points has been presented by Butler and others (1929, p. 101—127) and Broderick and others (1946, p. 690—693, Knowledge of the reasons for the location of individual ore deposits and of the district itself, therefore, must stem at least in part from an understanding of what lies down the dip from the present deposits, where the copper presumably came from. This area is deeply buried, and we cannot hope to inspect it, but we can make some educated guesses about it, based on what can be seen at and near the surface. 696—697). Keweenawan Paleogeography The Keweenawan basin or syncline was formed primarily by downwarping during or since latest Keweenawan time. Even the youngest Keweenawan rocks locally have nearly vertical dips. The basin is also a basin of accumulation; that is, the downwarping began during the time the lavas and sediments themselves were filling the present basin. This s shown by the fact that the malorstrati— graphic units thicken down the dip toward the center of the basin. Evidence for the direction of flow of the lavas nearly everywhere indicates that the lavas have flowed outward from the center of the basin towards the margin. Pipe amygdules at the base of lava flows commonly show southward flow in the Michigan copper district (Butler and others, 1929, p. 26— 27) and westward flow on the Minnesota coast (Sandberg, 1938, p. 818—820). This evidence for flow toward the margin has generally been taken to indicate that the vents themselves were located in the center of the basin, but this need not necessarily be true. As will be shown below, the copper district probably lies closer to the center of the present basin than any part of the Lake Superior region in which lavas of middle Keweenawan age are now exposed, but so far as is known, it contains no dikes that might have served as feeders. In contrast, dikes and sills are fairly common in the Keweenawan series of Minnesota, farther from the center, and many unmetamorphosed basaltic dikes that may well be Keweenawan in age cut the Huronian rocks that surround the Keweenawan basin (Van Hise and Leith, 1911, p. 411). Lava extruded anywhere within, or even on the rim of a physiographic basin would flow to the lowest point and then spread out from there. Outward spreading of the lavas from the center of the basin, therefore, does not necessarily indicate that the feeders were in the center, and the distribution of dikes suggests that many of the vents, at least, may have been at or outside the margins of the basin. The petrology, abundance, and distribution of so—called Keweenawan dikes throughout the Lake Superior region deserve more study. 5 �Some conglomerate beds seem to have been deposited by streams flowing inward from the margins of the basin. This is shown by foreset beds and imbrication of pebbles in the Houghton conglomerate (White, 1952), and by foreset beds in the Baltic (No. 3) conglomerate at the Champion mine (most southwesterly mine on Baltic amygdaloid as shown on Figure 2). The conglomerates and sandstones of late Keweenawan age on the south limb of the basin contain numerous foreset beds, and these consistently indicate northward flow of streams. Finally, the middle, and particularly the upper, Keweenawan sedimentary rocks contain fragments of pre—Keweenawan metamorphic rocks; these could hardly have been carried into the basin by streams flowing outward from the center. If the lavas flowed toward the margin of the basin, and streams depositing conglomerate beds flowed toward the center, we have an apparent paradox — one or the other would seem offhand to have flowed uphill. The paradox can be resolved if the floor of the basin was nearly flat, and if t was being more or less continuously warped downward by tectonic movement to form the basin. As long as filling by lava kept pace with downwarping, the lava surface would be essentially flat or slope very gently toward the margins (cf. Sandberg, 1938, p. 818, 820—821), and streams could not extend out into the basin. They would presumably be ponded at the margins (cf. Fuller, 1950, p. 67, and Pardee and Bryan, 1926, p. 15—16, on the Columbia River basalts), or be diverted to flow parallel to the margin of the basin. When extrusion of lava was interrupted for any extended period of time, however, continued downwarpng would then produce a topographic basin into which streams could flow, depositing conglomerate beds. Conglomerate beds, therefore, represent interruptions in the steady accumulation of lava flows, It may be very significant that the first flow of lava above conglomerate beds, that is, the first flow after such an interruption, is very commonly a flow of extraordinary thickness (Broderick, 1935, p. 553—554); if the steady downwarping of the basin was more or less compensated isostatically by lava filling the basin, the longer such compensatory filling were postponed during an interruption, the greater might be the outpouring that terminated the interruption. Although in a general way the present tectonic basin probably coincides with this ancient basin of accumulation, the margins of the first are not everywhere parallel to the margins of the second. In the Michigan copper distrct, the present strike of the beds is northeast, but the flank of the old basin of accumulation seems to have had a more easterly trend here. Several criteria suggest this more easterly trend. (I) Though reliable data are scarce, the best available evidence indicates that major strati— graphic units generally increase in thickness down the dip (Butler and others 1929, pI. 20, provides the best example), as would be expected in a basin, If this thickening is more or less normal to the basin margin, lines of equal thickness, or isopachs, should be more or less parallel to the basin margins. Figure 3 shows the general orientation of isopachs at two places; the symbol at Calumet is based on the stratigraphic distance between the Allouez and the Calumet and Hecla conglomerates in the Calumet and Hecla mine; the symbol farther northeast represents the trend of lines of equal thickness of the Greenstone flow at the Allouez No. 3 mine. A dike, apparently fed from the interior of the flow while it was still molten, cuts the upper I. All the orientation features of Figure 3 have been corrected for the present dip of beds; they are shown with the orientation the features would have if the beds were tilted back to the horizontal. 6 �Fig. 3 — Features suggesting orientation of ancient margin of the Keweenawan basin part of the Greenstone flow 9 miles northeast of Calumet. This dike is at a place where the Green— stone Flow thins abruptly from over 1000 Feet to less than 500 Feet (Davidson and others, 1955), and seems to be more or less parallel to the axis of thinning; it is here assigned the-same significance as an isopachous line, though the apparent parallelism may be just a coincidence. (2) Another feature, here called pinchand_swellh1, has the same general east—west orientation. The fragmental tops of individual lava flows are typically thicker in some places than in others, as has been described at some length by Butler and others (1929, p. 31—32). An amygdaloidal flow top can range in thickness from less than 5 feet in the thin places to over 60 feet in the thick. An isopach map of a given arnygdaloidal flow top, plotted in the plane of the top, might show either irregularly interspersed patches of thick and thin fragmental amygdaloid or highly elongate bands of thick amygdaloid separated by parallel bands of thin. The widths of individual bands of thick or thin flow top range from a few tens to a few hundreds of Feel, and their length may be measured in thousands. These alternating bands of thick and thin amygdaloid are presumciby primary features that originated as the lava flowed. The orientation of elongate patches of thick and thin fragmental amygdaloid (pinch—and—swell) can be measured locally where the patches happen to be well exposed in accessible mine workings, but the evidence for their orientation at most places is indirect. Thickness of fragmental amygdoloid is at least one important factor affecting the location of ore shoots within the major deposits; the thicker parts of a copper—bearing flow top are generally more favorable than the thinner (Butler and others, 1929, p. 109, 192, 200—201, 219), and lean or barren streaks that are controlled by thinness of the flow top are conspicuous on stope maps and grade maps of some mines (Butler and others, 1929, pls. 39-49). Though for many reasons it would be most hazardous to use a grade or stope map as a faithful representation of the distribution of thick and t}in fragmental amygdalod, most large and prominently elongate rich and lean streaks probably reflect differences in thickness (pinch—and— swell) where they are not related to faults or crosscutting veins. The orientation of pinch—and—swell of flow tops as inferred from stope and grade maps is shown in Figure 3. Assuming that this structural feature formed during flow of the lava, one w"-' 7 �it to be either a feature that lies parallel to the direction of flow or perpendicular to it. The general parallelism of the pinch—and—swell with the two isopachous lines is apparent, so it is assumed that the pinch—and—swell lies perpendicular to the direction of flow of lava, and generally parallel to the margin, or shoreline, of the basin. (3) The three arrows in Figure 3 show the direction of stream flow as suggested by primary features in certain conglomerate beds interbedded with the lavas. The arrow north of Catumet represents the direction of flow of the streams that deposited the Houghton conglomerate as shown by imbrication of pebbles and foreset bedding (White, 1952). At the Allouez No. 3 mine, where these measurements were made, the Houghton conglomerate attains thicknesses of more than 25 feet along an axis striking slightly west of north, and thins to a foot or less within 1500 feet to the east and west of this axis. This axis is presumed to coincide, more or less, with the direction of flow of the stream or streams that deposited the conglomerate bed. Similar axes can be drawn parallel to thick parts of the Calumet and Hecla conglomerate in the Calumet and Hecla mine (Butler and others, 1929, p1. 38, "Plan showing thickness of lode"). The arrow west of Calumet represents the orientation of these axes. The absolute direction of stream flow — whether north—northwest or south—southeast — has not been established beyond question in the Calumet and Hecla mine, and the workings are inaccessible at present, so the head of the arrow may conceivably be shown at the wrong end; the head is shown at the north—northwest end by analogy with the arrow for the 1-loughton conglomerate because the lens of Houghton conglomerate at the Allouez No. 3 mine is in many detailed respects a small—scale replica of the lens of Calumet and Hecla conglomerate at Calumet. The arrow southwest of Houghton represents the direction of stream flow shown by foreset beds in the Baltic congtonierate at the Champion mine. The direction of flow here seems to have been nearly at right angles to the direction at the other two localities. At the other two localities, the direction of flow is normal to isopachs, and is presumed to be normal to the basin margins. The direction of flow at the Champion mine would thus seem to have been parallel to the basin margin, and may represent a stream diverted along the edge of a lava flow that spread out from the center of the basin. To sum up the evidence afforded by primary features of the lava flows and conglomerate beds, these features have two distinct trends at right angles to one another (Fig. 3), one slightly north of east and the other slightly west of north. These features can be logically related to the orientation of the ancient basin margin or "shore lines", and indicate that the margin trended slightly north of east in the area of the Mchigan copper district. The present strike of the rocks is northeast, diagonally across the trend of the ancient margin, so we may infer that the rocks northeast of Calumet, for example, represent more central parts of the ancient basin of accumulation than the rocks southwest of Houghton. The useful application of these orientation data will be discussed after consideration of the gross structure of the basin as a whole. Structure of the Keweenawan Basin Tangible evidence for the configuration of the Keweenawan basin is only fragmentary. The Keweenawan rocks are completely buried by younger sediments in the vicinity of Minneapolis and farther southwest, and perhaps also in parts of the peninsula between Lakes Superior and Michigan (Fig. I). East of Ashland, Wisconsin, the whole central part of the basin is covered by the waters of Lake Superior, and even the rim is under water in over 95 percent of the area east of the longi— 8 �hide of Keweenaw Point (40 miles east of Calumet). Attempts to determine the shape of the basin, therefore, must be based primarily on extrapolation from the attitudes of the rocks in the relatively small proportion of the whole area where they are exposed. When magnetic and gravmetrk data ace available for the whole region, particularly the area covered by Lake Superior, our present guesses can be considerably refined. The general attitude of bedding is known in all the areas where middle and upper Keweenawan rocks are exposed (Fig. ). In places like the copper district and a few others it is also possible to measure locally the rate at which the dip flattens toward the center of the basin. West from the longitude of Keweenaw Point, therefore, cross—sections can be constructed with some degree of control on both sides of the basin, In drawing sections, one has some latitude in the selection of curves used to connect the dips on opposite flanks. One can, as one exfreme, assume that the dips flatten rapidly toward the center of the basin, and that the beds are horizontal over most of the basin, beginning just a few miles in from the upturned margins of the basin; this construction gives a minimum depth for the structural basin. At the opposite extreme, one might assume that the curvature s more or less evenly distributed across the entire width of the basin; this construction gives a maximum depth for the structural basin. The second extreme — uniform distribution of curvature — is demonstrably in error in the copper district, where not only the dip but also the rate of flattening (rate of decrease of dip) generally decrease toward the center of the basin. Another rough limit is set by the known thickness of the Keweenawan rocks; the lavas of middle Keweenawan age are probably of the order of 20,000 feet thick in the copper district2, and these are overlain by at least 15,000 feet of sedimentary rocks of late Keweenawan age. The minimum depth of the base of the lavas in the center of the basin is therefore of the order of 35,000 feet, and may be greater if the stratigraphic units thicken appreciably toward the center of the basin, as they seem to do. Within these various limits, the most reasonable constructions that can be made suggest that the base of the lavas lies somewhere between 35,000 and 50,000 feet below sea level in the middle of the basin. By drawing sections across the basin at intervals, assuming some particular type of curvature, one can develop a structure contour map that shows the shape of the basin. Figure 4 shows such a structure contour map; this particular example is based on the assumption that the sharpest curvature is on the south limb, where the dips are steepest, and gives almost a minimum depth — the horizon contoured lies 15,000 feet or more above the probable base of the lava series. The general shape of the basin is about the same if other assumptions are made, and the principal difference introduced by these other assumptions is in the absolute depth. The general position of the deepest part is not materially changed. This is a logical consequence of the fact that the dips are gentler on the north limb than on the south - this asymmetry makes the deepest part lie nearer the southern limb almost regardless of the type of curvature assumed. Over 15,000 feet of lava are exposed in a single section in the Delaware quadrangle (Cornwall, 1954), a little east of the main part of the copper district, and here, as in the copper district proper, an unknown but probably large thickness of lavas at the base of the middle Keweenawan is cut out by the Keweenaw fault. 2. 9 �6- -0 \— LL0UEZ CONGLOMERATE BED DIAGRAMMATIC STRUCTURE CONTOUR MAP OF PART OF LAKE SUPERIOR BASIN 50 MILES Fig. 4 — Contours in thousands of feet, represent the approximate depth below sea level of the horizon of the Allouez conglomerate; this bed is probably at least 15,000 feet above the base of the lava series over most of the contoured area. The principal chance for error in a construction like Figure 4 lies in the possibility that there are important faults or reversals of dip out in the basin. Little can be done to evaluate or attack this particular problem without geophysical data in the area covered by Lake Suprior. Figure 5 is a highly simplified and locally modified version of Irving's map (1883, pl. 28) TED. Hibbing MIDDLE KEWEENAWAN LAVAS EXPOSED .— —' Minn€ois/ ( St. Paul 0 _- / GENERAL OUTLINE OF MIDDLE KEWEENAWAN GEOSYNCLINE. Form line contours, generalized after Irving, suggest configuration 200 Miles 00 Fig. 5 — Form—line Contour Map of the Lake Superior Basin Northeast of Minneapolis. Numbers refer to areas mentioned in text. 10 �showing the general configuration of the whole basin or geosyncline northeast of Minneapolis3. The heavy line outlining the area of lavas of middle Keweenawan age has been added. Though the interval between Irving's form lines represents strafigraphic thickness rather than vertical depth, these lines are virtually synonymous with structure contours where the dips are gentle. The most central line (deepest contour) of Figure 5 is taken from Irving's map without modification, except for a little smoothing at the east end; the oval area outlined by the dotted line is the area enclosed by the 20,000—foot contour of Figure 4, reproduced here to show the general correspondence. The form lines at the east end of the basin are, of course, based on very scant data. Metamorphism in Depth We have no first hand evidence to tell us what modifications, if any, deep burial in the center of the basin may have induced in the Keweenawan rocks, particularly the lavas. The present thermal gradient at Calumet is remarkably uniform to a depth of 5,488 feet, and averages 18.1 ± 0.23° C/km (Birch, 1954, p. 19). Extrapolating this gradient to depths of 35,000 to 50,000 feet suggests that the present temperatures at those depths may be somewhere in the vicinity of 200° to 285° C. If the lavas accumulated fast enough to preserve some of their original magmatic heat wIthin the pile, temperatures in depth may well have been considerably higher in the late Keweenawan or early Paleozoic time than they are now. Temperatures of the order of 300° C probably characterize the higher grade parts of the green schist facies, if not actually the epidote—amphibolite facies. The fragmental tops of many of the lava flows must originally have been rather loose, rubbly After burial, their open spaces were presumably filled with ground water, and this water would be carried on downward as the lavas became ever more deeply buried. One can only speculate about the ultimate fate of this water and the permeable rock containing it when it was carried downward into a region where the lithostatic pressure was of the order of 2700 — 4000 atmospheres, and the temperature between 2000 and 3000 C, or higher. 5ome of the water would certainly combine with the rock minerals to form hydrous metamorphic minerals such as chlorite and perhaps actinolitic hornblende. The porous fragmental flow tops would be least partially crushed. The combination of crushing of the rock and heating would presumably drive some 9f the contained water toward the surface along the relatively open channelways afforded by the fragmental flow tops and conglomerate beds. aggregates. If we make the assumption, without attempting here to further bolster it with arguments from theoretical and experimental work on hydrous systems, that this water of essentially metamorphic origin was the principal agent of native—copper deposition in the middle Keweenawan rocks, we can develop from this assumption a logical structural reason for the location of the principal copper deposits. Location of the Copper District Perhaps the most interesting feature of Figure 4 is the position of the deepest spot. In any given bedding plane or flow top, the shortest path to the surface from this deep spot would lead to an area 3. A large positive gravity anomaly suggests that the syncline, with its associated lavas, extends southwest into central Kansas, where it abruptly terminates (Thiel, 1956, pl. I). •11 �at the southwest end of the copper district proper, which ends about 10 miles southwest of Houghton. If water of metamorphk origin were driven directly up the dip by heating and crushing in this deep spot, the maximum amount of water should emerge in the vicinity of and lust southwest of the mines on the Baltic amygdalod (Fig. 2), with decreasing amounts farther southwest and northeast. It is considered highly significant that all the important and most of the minor native—copper mines of the Lake Superior region are within 25 miles, horizontally, of the oval area bounded by the 20,000 foot contour in Figure 4. Less than 2 percent of the native copper from the region has come from beyond this 25 mile limit. Within this area of malor production, there is notably asymmetric geographic distribution of the producing mines. As noted above, the shortest path up the dip from the deepest spot would reach the surface 10 or 15 miles southwest of Houghton, at the southwest end of the copper district proper. The productive mines northeast of this point of emergence have yielded over 97 percent of the native copper produced in the region, whereas those to the southwest have yielded less than 2 percent. This proportion may be changed as exploration finds new deposits or as lower—grade ores are mined in the future, but it is nonetheless a remarkable difference, and one that requires explanation. The following explanation of the asymmetry is suggested. Earlier paragraphs described certain primary features oriented parallel to the basin margin. These include a structural feature here called pinch—and—swell", consisting of elongate patches in which the thickness of fragmental material in certain fragmental flow tops is appreciably greater or less than average. In the mines of the copper district, this linear element seems to be typically oriented nearly east—west (Fig. 3). In terms of permeability, the pinch—and—swell structure should make a flow top notably anisotropic — flow of solutions in a given flow top should be far easier in an east—west direction than in a north—south. Solutions moving up the dip from the deep spot shown in the center of Figure 4, therefore, would be continually steered off towards the east in their upward passage, producing the copper district proper where we now find it, rather than farther southwest, more nearly up the dip from the deep spot. To the extent that this explanation is correct, the lack of parallelism between the present strike of the rocks and the strike of the ancient basin margin is an important element leading to the localization, and perhaps even the existence of the Michigan copper district. Where the ancient basin margin and the present strike of bedding are parallel, the trend of the pinch—and—swell structure would not have a component parallel to the dip of the bedding, and up—dip movement of solutions would be relatively inhibited; flow should take place more readily, under the same hydrostatic pressure, where the pinch—and—swe1 rakes up the dip. Summing up, two structural conditions may govern the very limited distribution of native copper deposits. First, the copper district proper is very close to, and almost up the dip from a particularly deep part of the Lake Superior basin. Second, the copper district lies on the limb of a major identation in the flank of the Lake Superior basin (see Fig. 5), in a place where the present margin is not parallel to the margin of the old basin of accumulation. Primary structural features like the pinch—and—swell structure rake up the dip in this area, providing conduits leading from the deep spot to the surface. In places where the present and original basin margins are parallel, as they may be elsewhere, channels governed by the pinch—and—swell might be far less favorably oriented; these places would capture a smaller amount of the solutions moving out from the bottom of the basin. It should be emphasized at this point that the enrichment of-the Michigan district in copper is only relative; as was pointed out in the introduction, there are minor amounts of natve copper in 12 �the lavas all around the Lake Superior basin. In many places enough copper has been found to encourage extensive prospecting. In addition, the amygdaloids and conglomerates are filled with secondary minerals throughout the basin, lust as they are in the Michigan district. So mineralizing solutions have apparently moved upward and outward in all directions from the deeper parts of the asin4. The Michigan district seems to be unique only in that it may have captured more mineralizing water from the deepest parts of the basin than other areas — enough more to make the deposits commercial. As one possibility, more water may actually have flowed through the productive amygdalods of the copper district than through those of other areas because of the favorable system of channelways. Or, as another possibility, the water that fiowed through the rocks of the copper district may have contained more copper than elsewhere because it came from the deepest part of the basin, where the most crushing and metamorphism presumably occurred. Deposits in Other Parts of the Basin If channelways leading efficiently to deep spots in the Lake Superior basin are the chief factor in forming ore deposits, the chances for deposits in other parts of the basin can be at least roughly appraised. We can look first for other places in the region where the pinch—and—swell structure in flow tops rakes diagonally down the dip towards a deep spot. The type of information needed to definitely establish the trend of the pinch—and—swell structure can only come from rather extensive underground exposures, so outside the copper district one must depend on indirect evidence. The copper district lies on the west flank of a major indentation in the present basin (Fig. 5). The form lines that define this indentation in Figure 5 are arcs, and the trend of the pinch—and— swell structure in the copper district can be approximated by chords of these arcs. This is perhaps tc be expected if the indentation is not a feature of the ancient basin of accumulation, but is a later feature of tectonic origin — the trend of features like the pinch—and—swell that are presumed to be parallel to the ancient basin margin should have a course that follows the gross configuration of the basin, unaffected by the indentation. A basis therefore exists for inferring an orientation of the original basin margin, and of the pinch—and—swell structure that seems to be parallel to it, where other indentations are superposed or the broadly arcuate form of the basin as a whole. Two such indentations appear on Figure 5, one just west of Michipicofen Island (Area 9) and another at Isle Royale (Area 7). Chords across the arcs in the form lines at Michpicoten Island strike northwest, and at Isle Royale they strike east— northeast. Channels with these orientations at these places would not, apparently, rake down into particuJary deep parts of the basins. Solutions would have to cross the inferred trend of channels at both places to reach the surface from the deepest adjoining part of the basin. So in respect to channelways governed by pinch—and—swell, at least, the ideal conditions of the Michigan copper district do not seem to be repeated in any other place where middle Keweenawan rocks are now exposed at the surface. The most promising place for a repetition of the ideal condition is on the east flank of the indentation which bears the copper district on its west flank — unfortunately this 4. The ubiquitousness of the native copper and its associated secondary minerals in the lavas hroughout the area of the Lake Superior basin — an area over 400 miles long and 100 miles wide — an important reason for looking to some process of regional extent, such as is suggested here, ither than to local intrusive bodies, as a source for the copper and associated minerals. I3 �area is well covered by Lake Superior. In one other area, about 45 miles west of Ironwood (east end of Area 5, Fig. 5), channelways probably rake down the dip, but the structure of the basin in this area is too little known to permit an estimate of the relative depth of the basin into which such channelways might lead. Proximity to deep spots is the second basis for search for other favorable areas. Southwest of the copper district proper, in an area 15 to 40 miles southwest of Houghton, there are a number of mines which have produced over 5 million pounds of copper apiece, even though the total production from this area is less than 2 percent of the total for the region. This indicates that commercial deposits can be found even where channelways controlled by the pinch—and—swell structure may not be favorably oriented. This area lies directly up the dip from the particularly deep spot in the center of Figure 4, so proximity to a deep spot alone may give some promise of productive deposits. This makes worthwhfle a general appraisal of other parts of the Lake Superior basin in terms of simple proximity to deep spots, neglecting the factor of the channeiways. Even a crude structure contour map such as Figure 4 or 5 shows that because of the asymmetry of the basin, the deepest spots are probably down the dip from the places where the dips at the surface are steepest. If the dip on one side of the syncline is 10 degrees, as it is along most of the Minnesota shore nort,east of Duluth (Area 6, Fig. 5), the trough of the syncline is probably closer to the southern shore, where the dips of the lava flows are everywhere steeper. So in a very rough way one can conclude that the steeper the dip, the better the chance that a given area is close to a deep spot. Other things being equal, furthermore, the basin is probably deeper in places where it is wide than where it is narrower. Using dip and width of the basin as our main criteria, therefore, we may roughly appraise the promise of individual areas around the basin. In the area IS to 40 miles southwest of Houghton (Area 2, Fig. 5), the lava flows dip between 45 and 700. This area, which has produced over I percent of the copper from the region, is probably second only to the copper district proper in terms of future promise. Between this area and Ironwood (Area 3, Fig. 5), the dips are gentler, and the normal homo— clinal dip toward the basin is interrupted by the Porcupine Mountain dome or anticline, 30 miles northeast of Ironwood. Only the uppermost lava flows of middle Keweenawan age are exposed at the surface in this anticline, and the core of the fold is rhyolite (Butler and others, 1929, p. 47, 50 and pl. 14). This whole area in and south of the Porcupine Mountain uplift would seem to be distinctly unfavorable for important near—surface copper deposits in amygdaloidal flow tops and associated conglomerate beds. In terms of steepness of dip alone, the most favorable place in the region is north and northwest of Ironwood (Area 4, Fig. 5) where the dips are nearly vertical. Another factor complicates the evaluation of this area, however: A little farther west, in Area 5 (Fig. 5), both the north and south limbs of the Lake Superior syncline are separated from the center of the basin by thrust faults that repeat the middle Keweenawan section (Fig. I). The fault shown alona the. northern boundary of the lavas of middle Keweenawan age west of Asmand is calieci tne Douglas fault, and the fault separating the two slivers of the lavas 10—40 miles southwest of Ashland is called the Lake Owen fault (Aldrich, 1929, p. 125—126). The Douglas fault divides the north limb into two belts, in both of which the rocks dip southeast. In the same way the Lake Owen fault divides the south limb into two belts, in both of which the rocks dip northwest. These faults effectively separate the outer belts from the center of the Lake Superior syncline. Exposures are very poor in the area of younger sandstones east of Ashland. If the Lake Owen fault continues farther northeast, the lavas north of Ironwood may not be physically continuous with those in the center of the syncline, and the favorable 14 �conditions are not fulfilled. In Area 5 (Fig. 5), south and southwest of Duluth in Douglas and Bayfield Counties, Wisconsin, both limbs of the Lake Superior syncline have dips ranging from 30—45° (Grant, 1901, p. 21). Although these dips are of favorable steepness, the syncline is rather narrow here, so the maximum depth of the lavas may not be much more than 25—30,000 feet. This is distinctly less favorable than the areas farther east, where the basin is much wider and probably deeper. A number of showings in Wisconsin have been explored by small prospect shafts, but none have developed into mines. Along the Minnesota shore (Area 6, Fig. 5), the rocks dip between 10 and 15°. The dips are even gentler around Nipigon Bay (Area 8). These are the least favorable parts of the Lake Superior basin on the basis of dip. On Isle Royale (Area 7, Fig. 5), most of the lavas dip between 15 and 25 degrees (Lane, 1898, pl. I). This area is more favorable than any other on the north shore, but is less favorable than most of the south shore. At the east end of Lake Superior and on Michipicoten Island (Area 9, Fig. 5), dips locally exceed 40 degrees. Information on the east end of the basin is extremely sketchy, because so much of the Lake Superior sync line is covered by water, but unless there are unknown structural or stratgraphic complications, this area should be more Favorable than anywhere along the north shore, including Isle Royale. It may well be more favorable than the Wisconsin area (Area 5), though explorations do not seem to have been very successful to date (see Thomson and others, 1952, p. lO- II). To sum up, the basis for appraisal used here suggests that the most promising area outside the copper district proper is the area southwest of it (Area 2), extending to a point some 40 miles southwest of Houghton. The area north of Ironwood (Area 4) may be even more favorable, but its promise is clouded by the possibility that it may be separated from the deeper parts of the syncline by a fault. Michipicoten Island (Area 9) and the areas in Wisconsin (Area 5) on both limbs of the syncline south of Duluth are next in order of favorability. There is one small area 45 miles west of lronwood, on the south limb of the syncline, that is a more favorable prospect than the rest of Area 5because of the possibility that the pinch—and—swell structure may rake diagonally up the dip there. Isle Royale (Area 7) is probably less promising than any of the areas mentioned above, but distinctly more promising than the areas of gentle dip on the north shore in Minnesota and Canada. Acknowledgments A speculative essay of this sort necessarily draws on the work, some published and some unpublished, of many people. So far as I know, I am solely responsible for the particular uxtapo— stions of fact and theory presented here, but individual elements have come from many sources. am much indebted to my colleagues in the U. S. Geological Survey's study of the Michigan copper district, particularly Henry R. Cornwall and Richard E. Stoiber, for the contribution their researches along different lines have made to development of the ideas expressed here. I owe special thanks to Dr. Thomas M. Broderick of the Calumet & Hecla Inc., not only for his willingness to share with the Survey party his unequaled knowledge of the geology of the Keweenawan series, but also for the challenge his well—founded advocacy of a magmatic origin has kept before us. I 15 �References Cited Aldrich, H. R., 1929, The geology of the Gogebic iron range of Wiscbnsin, Wisconsin Geol. and Nat. History Survey Bull. 71, 279 P. Bateman, A. M., 1950, Economic mineral deposits, 2d ed., New York, John Wiley & Sons, 916 P. Birch, Francis, 1954, Thermal conductivity, climatic variation, and heat flow near Calumet, Michigan, Amer. Jour. Sci., vol. 252, P. 1-25. Broderick, T. M. 1935, Differentiation in lavas of the Michigan Keweenawan, Geol. Soc. America Bull., vol. 46, p. 503-558. Broderick, T. M., HohI, C. D., and Eidemiller, H. N., 1946, Recent contributions to the geology the Michigan copper district, Econ. Geology, vol. 41, p. 675-725. Butler, B. S., Burbank, W. S., and others, 1929, The copper deposits of Michigan, U. S. Geol. of Survey, Prof. Paper 144, 238 p. Cornwall, H. R., 1954, Bedrock geology of the Delaware quadrangle, Michigan, U. S. Geol. Survey Geologic Quadrangle Map GQ 53. Davidson, E. S., Espenshade, G. H., White, W. S., and Wright, J. C., 1955, Bedrock geology of the Mohawk quadrangle, Michigan, U. S. Geol. Survey Geologic Quadrangle Map GQ 54. Fuller, R. E., 1950, Structural features in the Columbia River basalt, Northwest Science, vol. 24, p. 65-73. U. 5., 1901, Preliminary report on the copper—bearing rocks of Douglas Co., Wisconsin, Geological and Natural History Survey Bull. 6 (2nd ed.), 83 p. Irving, R. D., 1883, The copper—bearing rocks of Lake Superior, U. S. Geol. Survey, Monograph Grant, 5, Lane, 464 p. A. C., 1898, Geological report on Isle Royale, Michigan, Michigan Geol. Survey, vol. 6, 281 p. C. K., Lund, R. J., and Leith, Andrew, 1935, Pre—Cambrian rocks of the Lake Superior region, U. S. Geol. Survey Prof. Paper 184, 34 p. Lindgren, Waldemar, 1933, Mineral deposits, 4th ed., New York and London, McGraw Hill Book Co., 93Op. Pardee, J. T., and Bryan, Kirk, 1926, Geology of the Latah formation in relation to the lavas of Columbia Plateau near Spokane, Washington, U. S. Geol. Survey Prof. Paper l4OA, P. 1—16. Sandberg, A. E., 1938, Section across Keweenawan lavas at Duluth, Minn., Geol. Soc. America Leith, Bull., vol. p. 795-830. Edward, 1956, Correlation of gravity anomalies with the Keweenawan geology of Wsconsin and Minnesota, Geol. Soc. America Bull., v. 67, P. 1079—1100. Thomson, J. E., and Resident Geologists, 1952, Preliminary Report on copper, nickel, lead, and zinc deposits of Ontario (Second edition, May 1952), Ontario Dept. of Mines, Preliminary Report 1952-4, 21 p. Van Hise, C. R., and Leith, C. K., 1911, The geology of the Lake Superior region, U. S., Geol Survey Monograph 52, 641 p. White, W. S., 1952, Imbrication and initial dip in a Keweenawan conglomerate bed, Jour. Sed. Petrology, v. 22, p. 189-199. Thiel, 16 �COPPER MINERALIZATION AT THE WHITE PINE MINE ONTONAGON COUNTY, MICHIGAN by John R. Rand (Abstract) The White Pine orebody lies in gently—dipping laminated to massive shaley siltstones at the base of the Nonesuch formation of Upper Keweenawan age. Fine— to coarse—grained sandstone lying within and immediately below the ore column is generally not of commercial interest, although locally such sandstone may be quite strongly mineralized, primarily with native copper. Copper mineralization over most of the know orebody consists of an extremely fine—grained dissemination of chalcocite, with native copper occurr-ing in amounts of secondary importance; bornite, pyrite, and chalcopyrite occur in minor or trace quantities. Native silver is present in sufficient quantity to be of commercial interest. Within a 20 foot ore column, the heaviest mineralization is restricted to four distinct lithologic units with an aggregate thickness of about six feet. A significant amount of copper occurs in two additional units with a total thickness of about four feet. The remaining units are only slightly mineralized. The four units carrying the heavy copper mineralization are dark gray to black, thinly laminated shales or siltstones, with some fine—grained sandy zones in two of the units. All other units in the column are medium gray or lighter in color, or are red or brown, and range litho— logically from thinly laminated shale through laminated or massive siltstone to sandstone with or without shale laminae. The striking association of copper with specific lithologic units over a wide area suggests that mineralization occurred essentially contemporaneously with sedimentation in a restricted shallow basin, and that the chemical environment in which certain beds were deposited controlled precipitation of copper from the overlying waters. The copper is considered to have been derived originally from the Lower Keweenawan Portage Lake Lava Series, released by weathering and oxidation into surface and ground waters. For a detailed description the reader is referred to White, Walter S. and Wright, James C., "The White Pine Copper Deposit, Ontonagon County, Michigan:" Economic Geology, Vol. 49, No. 7, pp. 675-716, November, 1954. — Ed. 17 �COMMENTS ON PRECEDING PAPERS by 1. M. Broderkk I think we should first discuss the source of the copper. Mr. 1, R, Rand; Copper is an original constituent n the Javas about the Lake Superior dstrkt, and by weathering and erosion of these lavas copper could be oxidized and liberated into ground wafer or surface wafer for the purpose of eventually going to form the deposits in the muds and clays of the present shales. It is not necessary to erode an ore body but mereiy to break down a large volume of rock which contains a small amount of copper. Dr. Broderick: True enough, both White and Rand agree on the source of the copper being the small dissemination in the lavas. Some years ago I very carefully sampled "traps" in this disfrct as we had them exposed from top to bottom in hundreds of drill holes; did not do the sampling in hundreds of drill ho'es but rather picked out places where the sampflng through several of the flows could be made very accurately. I had chemical analyses made; the Geological Socefy of Amerka gave me a grant for this study which was mainly on differentiation of the flows and I came up wth an average copper content of these traps of /lOO of a percent. If anybody could sample them any better, I would like to see it done. Dr. Goldkh of the University of Minnesota Laboratory used those same samples for a more exacting study of minor and trace elements and he checked that amount. Now I had recently gone through Washington's tables1 and as I suspected the copper content of these traps was not at all unusual; just recently I wrote again to Dr. Goldrkh and asked hm about the latest figures that he had seen and been able to assemble on the average copper content of rock and we find that the copper content of these traps s still rather low. He gave me average figures, quoting: the content of copper n igneous rocks in general, .007% average and in basaltk rocks in general, a recent figure .0085%. Steiger found 0.0155% copper in a composite of 71 Hawaiian lavas. Michigan tavas contain less than that. The greenstone flow has .012 and, if you do not like taking a flow that does not cont&n an ore deposit, the Kearsarge flow has .009, lust under the /OOth of a percent. So I do feel rritated with references to the copper content of these lavas to explain an unusual district. Other than that, we are in pretty good agreement; the deposits are epigenetic, we agree, not speaking of the White Pine, but in generaJ the deposits are epgenetic — they are formed by ascending hydrothermal solutions and there was a structural control of some sort. I would think of the structural control as both introducing or allowing the copper to be introduced into the channeiways I at depth and Dr. White has hs sfructura control as ndicatng where the flow of solutions would take place. We both agree that on the way up there would be deflection of solutions by barrier conditions of various sorts. Now 1 think that there is considerabTy more thcrn a fortuitous conjunction of affairs envisaged by White if some other orign s to be considered. That is, the same conditions in depth that would cause this metamorphk exhalation of solutions, might be the explanation that I am lookng for as to how and where solutions from some magmatic source got into the lavas. I would think that the deeper the port of the section involved, the more likely there would be to be a tongue of some underlying intrusive that we like to call upon to furnish these solutions. Now how about I. Washington, H. S., "Chemical Analyses of Igneous Rocks, 1884 — 1913." Survey Prof. Paper 99, 1917. U. S. Geologkai �this underlying intrusive? There are some who do not like to think of a gabbro as giving off much water because they think of it as a comparatively dry melt. We do have one tongue of this Duluth gabbro which is the handy one to call upon. We have one protrusion of it here at Mount Bohemia and it is thoroughly altered, uralitized, and it has an association of chalcocite fissures around so that it is competent to give off solutions which bear copper. In recent years in the Duluth gabbro itself there has been a study of the suiphide content and it is sufficient for the several governmental geological surveys and bureaus to do a lot of sampling along the base for copper and nickel, and several companies have gone in there and had respectable drilling campaigns. Large sums of money cipparently have been and maybe still are being spent so far as I know. This puts the Keweenawan in a sort of metallogenetic province. The epoch started in the late Huronian and extended through the late Keweenawan. I have written Dr. Marsden of Duluth, Minnesota, regarding the age of the Sudbury norite; did not know but that we could make it late Keweenawan but I guess not. He says that t is post— Huronian and pre—Keweenawan or words to that effect; so it is pretty close to Keweenawan. And in the Sudbury area you have the differentiation of that norite giving you the red—rock facies, and you have the copper and nickel, and in the center of the basin you have the lead—zinc differentiation. In Point Mamainse, north of Sault Ste. Marie, Ontario, an exploration is now going on trying to develop commercial ore and they succeeded in doing it in cross fissures in the Keweenawan which contain chalcocite. In the Copper Mine River area, Northwest Territories of Canada, there are again basaltic lava flows and there are wide cross fissures that in places are very rich in copper in the form of chalcocite. I am making the point that in this metallogenic province native copper with associated chalcocite is a widespread thing. While genetically the White Pine situation may be a very attractive tree to look at, I am trying to see the bigger woods and it is pretty hard for me to take some interleaved deposits, inter—larded deposits, here in a shale with chalcocite, here in sandstone with native copper, here again in another shale with chalcocite, and pull them apart and say there is a syngenetic origin for one and an epigenetic Origin for the other. I In discussing objections to a hypogene epigenetic origin for copper in shale at White Pine, the points are made that had they been epigenetic the nose of the anticline would be a natural collecting dam, that the chalcocite deposits should have followed up that nose, and that they should be rich just underneath that pitching anticlinal nose. Well, there was considerable structural readjustment after those Nonesuch shales were deposited around the Porcupine Mountains; they are turned up vertically and I guess almost overturned in places. Once you get away from the local disturbance around the Porcupine Mountain uplift, the dip of the shales becomes normal, 10 to 12 degrees. I do not see why you will not allow me to lust have tFat little post—ore folding there in view of this steep upturning of the beds around the Porcupine Mountain fault only a couple of miles away. I have pointed out some of the things on which as 'defender of the faith" still want to base my thinking. It is along the lines announced long ago by Irving when he pointed out the native copper I ?n sediments, conglomerates, shales and sandstones, amygdaloids, cross—fissures and chalcocite in cross fissures and in the Nonesuch shale, and said that any acceptable explanation for these deposits must explain them all. Consequently lam looking very critically at anything that deviates from that. Maybe I will have to change my mind but I have not been induced to do so yet on the basis of anything that has been presented. I am giving up the idea of presenting comments on this series of papers as they are presented; I have lust written a brief announcement in Economic Geology referring to the fact that I am going feel that I would like to defer my written presentation until the major portions of these to do so; articles by the United States Geological Survey appear in print. find that it is very profitable because the longer I wait the less I have to criticize. I I 19 �COPPER DEPOSITS OF THE LAKE SUPERIOR REGION2 Sir: In 1946 I and my associates (I) published a paper in this Journal bringing up to date the facts and deductions of the Calumet & Hoc Ia geological group concerning the Keweenawan copper deposits of the Lake Superior region. This paper included a discussion of origin and reiterated a concept long recognized as fundamental by various geologists including Irving, Van Hise, Leith and Steidtman and the Calumet & Hecla group, namely, that a theory to be acceptable must explain all of the deposits of the district. These include the native copper deposits in amygdaloids, sediments, and fissures, and the associated sulphides, of which chalcocite s in great predominance, likewise in amygdaloids, sediments and fissures. In addition are the associated deposits of copper nickel and cobalt arsendes and antimonides, largely in cross fissures. The theory of the Calumet & Hecla group, formulated in the early twenties, still seemed to be the only one that satisfactorily explained the facts. Over a decade ago, a group from the United States Geological Survey started a study of the district and they are presenting a series of papers in which the origin of the copper deposits is treated. They do not share the belief that one mode of origin must explain all of the several types of deposit. Their papers, presented already (2), propose several modes of origin including both syngenetic and epigenetic and they have not yet treated the most important deposit thus far mined, the Calumet conglomerate, nor the mass copper, chalcocite and arsenide fissures. I have already discussed (3) the treatment of origin as given in the Cornwall papers I wish to discuss the more recent U.S.G.S. papers but in order to make it more definite that the evidence thus far presented does not lead me to abandon the idea of a single origin for all the occurrences, prefer to postpone the discussion until a larger number of their series has appeared. published in 1951. I Friends in teaching say they have a problem in that students show a tendency to accept the latest material published and realize that this is only natural. As soon as the Cornwall-White paper on "Native Copper Deposits" and the Stoiber—Davidson paper on "Mineral Zoning" appear, I shall try to publish some comments promptly. My discussion even then will be handicapped because a convincing presentation includes a treatment of the Calumet conglomerate and the mass copper, arsenide and chalcocite deposits in fissures. The U. S. Geological Survey treatment of these, I understand, will not appear for some years but I do not feel that I should wait that long for at least a preliminary comment on the papers listed (2). I In the meantime, students and others are referred to our 1946 paper (1) and my 1952 discussion (3). In these papers they will find that I have anticipated and commented upon most of the arguments which are being advanced for other explanations of the origin of these deposits. In addition to this discussion of origin which I hope to present as soon as a few more 2. Reproduced from Economic Geology Vol. 51, No. 3, with the permission of the Editor. 20 �of the Survey preliminary papers appear, I hope later to review the results of their entire project in the district. A start has been made on publication of their results of underground mapping in the mines and of quadrangle folios with the usual factual matter presented in such media. A local study of details of sedimentation led them to conclusions as to the source of the materials involved which are different from those hitherto regarded as most likely from evidence obtained on both sides of the Lake Superior syncline. It is hoped that before the Survey publishes further on this subject it will send in some specialists on processes of sedimentation and on significant characteristics of lava flows to study the broader aspects of the problem not only in Michigan but all around Lake Superior since the matter of location of the source of Keweenawan lavas and sediments is of fundamental importance. As stated by White, the determination of the source of the sedimentary material and "of the direction in which the ancient streams flowed is essential to a reconstruction of the physiography of the Keweenawan basin of deposition . . (which) in turn may prove helpful or even necessary to the geologic search for new copper deposits" (4). Perhaps before the final publication of conclusions, the evidence afforded in the openings of the Calumet conglomerate mine will again become accessible for study. . feel that my review of the topics of the survey other than those connected with the origin of the copper deposits had better be postponed until the final publication is out. An earlier discussion would be premature and would not be occasioned by the feeling of urgency offered by the debatable character of the topic of origin. In my final review I shall express appreciation for the completion of a long and tedious task, carried out with persistence and faithfulness and which at last provides the district with a set of useful topographic and geologic maps. 1. M. Broderick Calumet, Michigan I December 21, 1955 References I. Broderick, 1. M., HohI, C. D., and Eldemiller, H. N., 1946, Recent contributions to the geology of Michigan copper district: ECON. GEOL., v. 41, p. 675-725. 2. Cornwall, H. R., 1951, llmenite, magnetite, hematite and copper in lavas of the Keweenaw Series: ECON. GEOL., v. 46, p. 51—67. ——, 1951, Differentiation in lavas of the Keweenawan series and the origin of the copper deposits of Michigan: Geol. Soc. America, v. 62, p. 59—202. ——, 1951, Differentiation of magmas of the Keweenawan series: Jour. Geology, v. 59, p. 151-172. White, Walter S., and Wright, James C., 1954, The White Pine copper depost, Ontonagon County, Michigan: ECON. GEOL., v. 49, p. 675-716. Cornwall, H. R., and White, W. S., 1954, Native copper deposits: (not yet published) abs. Geol. Soc. America, v. 65, p. 1242—1243. Stoiber, Richard E., and Davidson, Edward S., 1955, Mineral zoning in the Portage Lake lava series, Michigan copper district: (not yet pub'ished) abs. Am. Inst. Mi & Met. Eng. Abstracts Mining, Geology, & Geophysics Div., p. 24—25. 3. Broderick. T. M., 1952, The origin of Michigan copper deposits: ECON GEOL., v. 47, p. 215-220. 4. White, Walter 5., 952, Imbrication and initial dip in a Keweenawan conglomerate bed: Jour. Sedimentary Petrology, v. 22, p. 189-199. 21 �POSTSCRIPT3 Since the foregoing was submitted for publication, it has been announced that Dr. White would The regional geologic setting of the Michigan native copper district" at an 'Institute on Lake Superior Geology" to be held at Houghton, Michigan, May II and 12. He has very kindly sent me an outline of his paper and it presents a treatment of origin of the deposits including source of copper, source of solvent, broad structural controls and other features. Any discussion of the ideas on genesis being presented in the series of U.S.G.S. papers should certainly await the publication of this latest one by White, in addition to those by Cornwall and Stoiber referred to present a paper above. Dr. White: I want to make only one point at this time. Dr. Broderick spoke of the .01% copper content of Keweenawan lava as though this was the source without any intermediate process. think should say that he himself pointed to one possible clue to this problem of getting a 100 to I enrichment. This is approximately 100th of the concentration that now forms an ore deposit so we have to look to some process or processes that will give us concentration of roughly 100 to I. Dr. Broderick found in his study that he referred to earlier that the individual flows were quite notably differentiated and he pointed also to the fact that one of the constituents that tended toward enrichment at the top think that this may give us a clue to at least a substantial fraction of this 100 to was copper itself. concentration that we are looking for, If, for example, the copper content of the massive flow that he sampled is .01 or .007, it may well be that this represents somewhat less than the average original content of copper in the flow itself. As he himself points out, some of this copper tends to work its way to the top, enriching the top and by the same token depleting the central portion of the flow. If the tops are enriched only by a factor of 2 or 3, say .02 or .03, we would have a good start toward 100 to I enrichment. This reduces the factor from 100 to to say 50 to I, maybe even down as low as 25 to I. This is a very hard thing to get hold of because it is almost impossible to sample a flow top, as think we all realize, and be sure that we are dealing with this enrichment which we can postulate took place at the time the flows were extruded. I am on thin ice as well in suggesting what the figure might be, but I do think that this initial concentration in the parts of the lava flow which are the porous flow tops if in reaction with the contained water, might yield copper to a solution in sufficient concentrations to form the hydrothermal solutions that we all agree form the ore I I I I I I deposrts. Mr. Rand: On the basis of Dr. Broderick's .01% copper it would require an area of traps 30 miles square to be eroded 12 feet deep in order to supply the 6 billion pounds of copper considered to be known in the White Pine orebody. This erosion and transport do not invlove movement of placer copper; it is a matter of oxidizing copper, taking it into solution and then carrying it, presumably in ground water, into or onto the flat basin area where muds are being laid down. It may be carried out over the muds in the surface waters or It may be carried beneath the muds in the ground water and in the sands underlying the muds. The movement of copper from the waters into the muds may take place essentially at the same time as the copper arrives over or under the muds or it may fake place at some time after consolidation of the muds into rock. Dr. J. W. Gruner (University of Minnesota): How does it happen that there is so little sulphur associated with the copper ores here if they are of regular hypogenefic origin? Ordinary copper 3. Economic Geology vol. 51, no. 3 22 �sulphide ores are very high in sulphur. In this region we have a very low sulphur content, relatively speaking of course, and this has rather bothered me for some time because the chemistry of these deposits evidently is different from the chemistry of the regular sulphide deposits. Dr. Broderick: Of course that is one of the big problems, why the copper is native and not suiphide. Without going into the history and details there are two obvious answers that might be considered; one is that the solutions that deposited the copper were different from those that brought them in at Butte, Morenci, and other places, and the other is the rock into which those solutions were introduced. If you examine the assays of the Butte batholith and of the monzonites and allied rocks in which the porphyry coppers are deposited, you will find that the iron content is very low. Total iron I believe is less than 2%. The total iron in the amygdaloids and in the conglomerate deposits in Michigan is from 6 to 9% and a large part of that iron is in the ferric state. Proceeding from there, if the iron was a precipitant, does it show any effects of having entered into a chemical reaction when the copper was deposited? It is a matter of common knowledge amongst those who have worked in these deposits that in certain zones, over a vertical range of thousands of feet around the copper, there is an alteration of ferric iron. The rock is red normally and around the copper is a halo of bleached material and that bleached material has been sampled and assayed; polished sections have been studied running across the boundary of the bleached and unbleached and it is low in iron. Little needles of hematite have been absolutely removed so that iron has entered into that reaction. Removal of iron is therefore associated with the deposition of native copper. As a further clue, the iron that does remain in some of these altered areas is much higher in the ferrous state than in the surrounding rock. If you have 4% ferric iron and 2% ferrous in the normal amygdaloid in the zone around the copper those ratios will be reversed — it will be much higher ferrous and lower ferric. Chlorite will be formed which has iron in the ferrous state so that the deposition of copper in certain parts of the zonal column, not the stratigraphic column, is associated with the reduction and removal of iron. Now if iron was reduced it means something was oxidized and we threw the ball to the chemists and asked them, "Supposing that we had copper—bearing solutions coming in here of the sort that deposited suiphide elsewhere, what might happen to the sulphur? Could it react with the ferric iron, reduce it, and go out of the system as a soluble sulphate, leaving native copper?" That work was taken up in the laboratory of the U. S. Geological Survey and a paper was put out by R. C. Wells.4 If you will go back and refer to that bulletin you will get this story that have just told you in brief. In summary, one answer to the question is that the solutions were the same as those which deposited copper in the porphyries but they hit a different rock, a rock that had oxidizing possibilities. I Dr. G. M. Schwartz (University of Minnesota): I suppose I might start by saying that I am probably the oldest timer of all because I worked in the district before Dr. Broderick, and probably before Dr. White was born and I would like to make two or three comments, because I find myself in agreement with both men, in part, and in disagreement with both, in part, and incidentally might say that, for thirty—five years since left this distrkt, have worked mainly in the Keweenawan in Minnesota. I was very much interested in Dr. White's comment as to why we do not have copper deposits in Minnesota to amount to anything. further say that think his is the best explanation have heard. I I I I I I I would like to point out on the problem of getting the copper out of the basa Its that in Minnesota 4. Wells, R. C., "Chemistry of the Deposition of Native Copperfrom Ascending Solutions." U. S. Geological Survey, Bull. 778, 1925 23 �at Susie Island, for example, there was a very nice copper Vein with calcite, bornite, chalopyrite and pyrite which is below the flows. Now I will grant Dr. White that the mineral—bearing solution possibly could have leaked out to the side, or downward, or something of that sort but I have a sneaking Suspicion that it did not. think that there is still a good argument for a hydrothermal origin rather than the old idea of lateral secretion which is essentially of course what Dr. White is proposing and is, incidentally, popular for many other deposits at the present time. I In regard, however, to the shale, I had a good look at that when I was fortunate enough to be called upon to examine the work in connection with the White Pine loan and I must say that there it is a lot easier for me to imagine the copper in the shale having been deposited with the shale, in other words being syngenetc. So there I would disagree with Dr. Broderick and agree with Dr. White and Mr. Rand. It does seem to me, however, that we are asking an awful lot of these weathering solutions to concentrate this minute amount of copper out of these flows and get it all in one place. There again I think that it is a little easier to imagine that the copper which is in the White Pine deposit probably came from the weathering of some of the copper deposits and if understand the geologic history correctly I think ths is entirely possible. I I would like to have either Dr. White or Mr. Rand comment on this. Of course we might even consider that there was a direct contribution to the water of copper From hydrothermal sources. This would be essentially going back to Van Hise and Leith's explanation of a possible origin of the iron in the iron formations. These are the points that have occurred to an old timer on this problem and I think it just keeps us going around more or less in a circle on how to explain these things. Dr. White: I would like to make one comment in answer partially to Dr. Schwartz and partially also to Dr. Broderick. This has to do with uniformitatianism. Mustwe explain everthing with the same set of rules? We have in this Keweenawan province an area of 50,000 square miles or more underlain by Keweenawan rocks. For an area of crystalline rocks this is substantial port of the earths crust. If we assume that ore deposits can be formed as we have suggested, does this preclude this area from being cut here and there by veins of magmatic origin? This is pretty hard to pin down but I cannot feel the same compulsion that others seem to share that we have to explain everything by exactly the same set of circumstances. The deposits are different; the Whte Pine deposits are about as unlike any of the lode deposits as one can imagine. The arsenide veins that cut some of the lodes are quite different from the normal types of veins which cut the lodes. I do not personally see any reason why we have to explain all these things by exactly the same set of rules when the area involved is so large. Dr. C. H. Burgess (Bear Creek Mining Company): It seems to me that the percentages of copper contained in the igneous rocks of various kinds, as Dr. Broderick read to us, indicates that both in 'traps" and in granite that might have differentiated from themare very small. They are of the same order of magnitude and therefore the production of a copper deposit depends upon the efficiency of concentration. In that regard the explanation of the White Pine by Messrs. White and Rand is somewhat in the framework of the pyrite and marcasite in the black shales of coal measures. I wonder if sulphides in coal measures must also have a hydrothermal origin. Dr. J. W Gruner (University of Minnesota): The explanaton that Dr. Broderick offered I had already read but I do not understand whether the solutions were acid or basic. Basic solutions do not bleach or leach iron at all; however basic solutions dissolve copper quite readily. Of course acid solutions both bleach and carry copper. That I think is one of the fundamental questions we have here. Dr. Broderick: Regarding sulphur and organic matter I cannot say very much, but I can take Dr. 24 �Burgess out into the bogs and stir up hydrogen suiphide. or igneous rocks around those bogs. I do not think that there are any lava flows I do want to say something about the adequacy of a large volume of rock with a small percentage of some constituent for furnishing concentrations. It is an easy matter to sit down and figure how many cubic feet or yards or miles of rock containing 1/1,000 or 1/1,000,000 or 1/10th ofa percent will, if you could get that all together, form deposits much richer, but the entire process studied in its entirety seems to carry rather some unlikely implications. We picture these lavas as being exposed, weathered and eroded, and nearly everything going into solution. Along with the copper, the zinc, lead and cobalt components will enter into solution. Let us imagine these traps being sublected to that process not over one season but certainly over centuries and maybe hundreds of centuries. Weathering goes on and the copper, lead, zinc, cobalt, etc., are carried by streams down wherever they go; weathering is not lust in the vicinity of the White Pine basin, it proceeds all along the Keweenaw Peninsula and all around Lake Superior. Now at some time and at some place in this area of hundreds of miles being eroded during thousands of years of time a sudden opportunity presents itself and you get this deposit. The White Pine depost is contained within a relatively few feet and is said to contain 300 million tons of rock carrying over 20 pounds of copper per ton; that is 6 billion pounds and it is only partly explored. This whole district in the hundred years that it has been mined has only produced 10 billion pounds. Here we are asked to believe that a minor episode in the erosion, weathering and solution of rock containing less than 0.01% of copper that have proceeded over the thousands of years and throughout the thousands of square miles of Keweenawan lavas around Lake Superior, suddenly, in a small fraction of the area and during a relatively few of the seasons involved has resulted in the precipitation of a deposit containing nearly as much copper as the whole district has produced to date. That is a difficult thing for me to understand. Mr. H. W. Pfeffer (ARASCO Exploration Company): I do not know this district very well but I would like to mention an area in Nova Scotia which has certain similarities to White Pine. There we have Carboniferous rocks that are mostly red beds but in some small spots within the red beds are sandstones, conglomerates and shales. The shales are grey to blackish and they contain carbonaceous matter, usually remnants of wood, etc. Associated with these beds are nodules, sheets and dissemina— tions of chalcocite. To the south of this area are the Copper Cliff Mountains which contain some pyrite and a little chalcopyrite in various spots throughout the volcanics. It appears from the way the Late Pennsylvanian rocks were laid down that the source was from that area and it seems quite likely that the copper must have come from there. There is no evidence whatsoever of intrusion into the Carboniferous rocks; the features are definitely sedimentary. One can visualize water carrying in solution copper sulphate in minute quantities and running off into this area of sediments and percolating through the sandstones, and then the copper sulphate reacting with the carbonaceous matter. Actually the occurrences are very simUar except for quantity. These grey rocks lens out so that economically they are not of interest but in their manner of occurrence and chemistry they are very similar to White Pine. 25 �GEOLOGY AND MINERAL DEP/OSITS OF THE MAN ITOUWADGE LAKE AREA* by E. G. Pye Introduction In 1931, the Manitouwadge Lake area was surveyed for the Ontario Department of Mines by Dr. J. E. Thomson, now Assistant Provincial Geologist; and on his geological map, published in 1932, he noted an occurrence of gossan and sulphide mineralization at the site of the now famous Geco mine1. But despite this it was only rently that any interest was paid to the discovery. This may be owing to the commonly held opinion that "greenstone" belts of small area do not lend themselves to the occurrence of large mineral deposits — the favourable prospecting area at Manitouwadge Lake is only about 35 miles square. It may also be because of the highly metamorphosed condition of the rocks— many prospectors consider that schists and gneisses are unfavourable to ore deposition. In any event, the area was avoided until as late as 1947, when the sulphide deposit at Manitouwadge Lake was first staked. But even at that time, it was difficult to arouse interest ine discovery; and after two years, the prospector, Moses Fisher, was compelled to let his claims lapse because of failure to attract a mining company to undertake development. In 1953, two prospectors, Roy Barker and William Dawidowich of Geraidton, Ontario, decided to visit the area. Upon relocating the sulphide deposit, with which they were much impressed, they decided to stake. The sulphide deposit was examined by W. S. Hargraft, consulting mining engineer, and upon his recommendation, the property was quickly taken up by General Engineering Company, Limited; Consolidated Howe>' Gold Mines, Limited; and H. W. Knight and associates on a partnership basis. Diamond drilling in August and September indicated the possibility of a copper—zinc—silver ore body. Geco Mines, Limited, was incorporated in October, and it was not long before the results of further drilling indicated a deposit of such importance that the biggest staking rush in the history of Ontario, and one of the biggest in the history of Canada, was precipitated. Location of Area, Means of Access The Manitouwadge Lake area forms a small but very important part of the Heron Bay - White Lake region along the north shore of Lake Superior. As shown in Fig. I, it lies about midway between two transcontinental railways, the Canadian National Railways line on the north and the Canadian Pacific line on the south; it is 170 miles east—northeast of the Canadian Lakehead, and 200 miles northeast of Houghton, Michigan. * Published by permission of the Provincial Geologist, Ontario Department of Mines. I. Thomson, Jas. E., uGeology of the Heron Bay - White Lake Area,' Ont. Dept. Mines, Vol. XLI, pt. 6, pp. 34—47 (with map No. 41), 1932. 26 �• Q:N 'I T.A A. • OLFX—LOOKO UT' A FORT rRANcES GRAND HARM MINNESOTA I SCALE OF MILES 40 80 120 ISO — S —• 0 MICHICAN Fig. I. S°' Key map showing location of the Manitouwadge Lake area. The area is accessible by an Ontario Department of Mines access road connecting Manitouwadge Lake with the Trans—Canada highway along the north shore of Lake Superior; by a spur railway line cuilt south from Hillsport y the Canadian National Railways; and by a second railway line, built north from Hernie by the Canadian Pacific Railway. General Geology All the consolidated rocks exposed in the Manitouwadge Lake area are of Precambrian age. They have been divided into three main groups: (I) A system of closely folded and intensely metampophosed volcanics and sediments, which, together with horizons of amphibole — biotite gneiss and banded iron formation, are believed be of Early Archaean age; (2) An assemblage of igneous rocks, of post—Early Archaean and possibly of Algoman age; and (3) Diabase dikes, which have been correlated tentatively with basic intrusives of Keweenawan age exposed around Lake Nipigon and along the northwest shore of Lake Superior. to The area! distributions of these principal groups of rock formations are shown on the generalized geological map of the area (Fig. 2). Early Archaean Volcanics: A prominent series made up largely of hornbiende schist is exposed south and east of 27 �___ MILES 0 r, 4 a a e as I 2 3 rç OIAtASE METAGABBRO IRON FORM. SEDIMENTS (I V0LC4(CS + 444'..(S) "t3++++++I :n:rr JWOWIJN flV it hair ++ UA++++t oaac.+++ nrrwt*r( .it'4i-i-t+ -+4* •fl. L.0+++4j T++++ +++ t* 4 iw'44+44+++c;44.atj.. ,4+ 4 444444++J(*4t _)i9( it +4 4+++ +4+ t + 4+4+ •t.P.#++ 1 4+5 p iJ so I Fig. 2. Generalized geological map of the Manitouwadge Lake area. Wowun Lake. It forms a well—defined belt, up to and possibly exceeding two miles in width, which extends from this locality southwest to Manitouwadge Lake, and thence westward across the southwest corner of the map area. Two varieties of hornblende schist are present. One shows little evidence of banding; the other is characteristically finely laminated and resembles a thin bedded sediment in structure. Excellent exposures of the non—laminated hornblende schist are found in the west part of the belt. In places where shearing has not been too intense, vestiges of original pillow structures can be seen. The pillows are somewhat irregular in shape and do not permit satisfactory top determinations. But their presence is significant, for they indicate that the hornblendeschist is of volcanic origin. In consideration of the mineralogical composition — the typical schist consists of about 50 percent hornblende with lesser amounts of andesine and a little quartz, sphene, and magnetite — it is probable that the rock is the metamorphosed equivalent of original basic lava. Thin horizons of laminated hornblende schist separate the lava flows. They are particularaly well developed in the vicinity of Manitouwadge and Mose lakes. The rock itselfis similar mineralogically to the variety just described except that, at the expense of plagioclase, quartz is an essential rather than an accessory constituent. A further and more striking difference, of course, is the thin bedded structure — black layers of material rich in hornblende alternate with grey layers rich in plagioclase and quartz. These layers range from a small fraction of an inch to several inches in thickness. The laminated hornblende schist is found in places to contain lenticular fragments of greenstone, from less than an inch to six inches in length arid up to about three inches in thickness. The two characteristics — stratification and fragmental structure — indicate that the original rock was a tuffaceous sediment deposited subaqueously during the period of volcanism. Sedimentary Gneisses: As the north margin of the volcanic series is approached, well—developed 28 �horizons of sedimentary gneisses are found to alternate with bands of hornblende schist. These increase in both number and thickness to the north so that, within a short distance, the series gives way to one in which the principal ferromagnesian mineral is biotite. Four principal varieties of sedimentary gneisses have been recognized. They are biotite gneiss, quartz—oligoclase—biotite gneiss, quartzite, and quartz-microcline gneiss. In view of the evidence presented by petrologists to the effect that clay minerals corbine to form chlorite and sericite, and that these in turn combine to form biotite during metamorphism , it is thought that the biotite gneiss, the quartz—oligoclase—biotite gneiss, the quartzite, and the quartz— microcline gneiss are the altered equivalents of shale, argillaceous sandstone, quartz sandstone, and arkose, respectively. Amphibole—Biotite Gneiss: In many places throughout the series the sedimentary gneisses are found to be ;nterrupted by lenticular masses of amphibole—biotite gneiss of dark colour, coarse to very coarse granularity, and striking appearance. This rock is made up largely of anthophyllite, hornblende, and biotite, with small amounts of quartz, oligoclase, and magnetite. Red garnets are also commonly present. They occur as large porphyroblasts, ranging from about one—half inch to two inches or more in diameter, and in places make up 25 percent of the rock mass. The amphibole— biotite gneiss is frequently found to grade, by disappearance of amphibole and, when present, also of garnet, into typical biotite gneiss. Because of this it is considered to be sedimentary origin — it may represent the highly metamorphosed equivalent of a calcareous, chloritic grit or basic tuffaceous sediment that was developed at the same time as the enclosing rocks. It is included with the sedimentary gneiss on the generalized geological map. Iron Formation: Commonly intimately associated with the amphibole—biotite gneiss is a peculiar banded rock. Tk1 banded rock consists of layers of coarse—grained quartz, from a fraction of an inch to a foot or more in thickness, alternating with equally thin or thinner layers of one or more of amphibole schist, garnetiferous amphibole—biotite schist, and a very coarse amphibolite. In the field it has been variously termed quartz—chlorite rock, quartz—amphibole rock, quartz-amphibole—pyroxene rock, and iron formation. Since the rock is distinctly banded, since the schist or amphibolite layers contain disseminatee crystals and thin seams of fine granular magnetite, since individual horizons can be traced by dip needle and magnetometer, and since these horizons are very persistent and follow the folded pattern of the sedimentary gneisses, it is thought that "iron formation" is the most appropriate term. Post-Early Archaean (Algoman?) Basic Metaintrusives: Small lenticular bodies of metagabbro are fourd in a number of places within or close to the belt of volcanic rocks. These bodies have intrusive relations with the Early Archaean formations, but are themselves cut by granite and pegmatite. For the most part they consist of a medium—to coarse—grained rock made up of about equal amounts of dark—green hornblende and plagioclase, with small amounts of biotite, quartz, and magnetite. This rock is generally quite massive in the outcrop. Granitic Rocks: The most abundant igneous rock found in the Manitouwadge Lake area is biotite Harker, Alfred, "Metamorphism, A study of the Transformations of Rock Masses," Methuen & Co. Ltd., London, pp. 45-61, 1950. 2. a 29 �granite gneiss. Together with massive granite, migmatite, and pegmatite, it occurs in three principal localities: (1) the extreme southeast corner of the area; (2) the extreme northwest corner; and (3) the whole of the northeast quarter. The granitic rocks to the northwest and southeast are telieved to represent a single large mass, in which the Early—Archaean rocks form a deeply infolded inclusion; those in the northeast quarter of the area are believed to represent a satellite of the main mass, which has been localized along the major synclinal axis (see Structural Geology). Associated with the granite gneiss, migmatite, and the medium—grained, massive, intrusive biotite granite, and cutting the Early Archaean formations, are dikes and sills of pegmatite and aplite. The pegmatite is of three ages. It occurs as: (1) dikes which cut metagabbro inclusions in, and which are themselves truncated by, the massive biotite granite; (2) irregular bodies which grade into, and hence represent a phase of, the massive biotite granite; and (3) dikes which cut the massive biotite granite. Some of the pegmatites are pre—ore in age, and on the properties of Geco Mines, Limited, and Willroy Mines, Limited, they were instrumental in the localization of the ore deposits. Algonkian The youngest rock exposed is diabase. The diabase forms a number of narrow, but fairly persistent north—south dikes, some of which are localized along transverse faults (see Fig. 2). In that these dikes cut sharply across all the other consolidated rocks, including the various granitic rocks, it is thought that they are of Algonkian or Late Precambrian age. It is possible that they could be correlated with similar rocks, of Keweenawan age, that crop out to the west of the area in the vicinity of Lake Ntpigon. Structural Geology Folding: The rock type described as iron formation is the only one that occurs in sufficiently distinct and persistent horizons to be useful in outlining the structural geology. Examination of the generalized geological map of the area shows that, in the vicinity of Wowun lake on the east, the iron formation and the gneisses strike southwest and dip vertically to steeply north. Proceeding westward to Fox creek and the GQco mine, however, the formations assume an east—west strike; and still farther west, midway between Fox and Nama creeks, they strike northwest and dip N. Finally, at the west side of the map area, the formations assume first a northerly strike and then double back on themselves to strike northeast again. They delineate a large trough or synclinal fold, which dip measurements indicate to be assymetrical and overturned to the north. Other dip measurements, at the nose of the fold, indicate a plunge to the northeast of from 15 to 25 degrees. In the eastern part of the area, lineation and drag folds indicate a steeper plunge of about 40 degrees. Faulting: After the major foiding, the Manitouwadge Lake area suffered a series of disturb'Dnces that iul1ed in the development of a large number of faults. These faults are of three types: (I) longitudinal or strike faults, which more or less parallel the formations along the south limb of the syncline; (2) transverse faults, which strike in a general north—south direction; and (3) diagonal faults, which strike northwest, obliquely to the other faults. All are represented in the field by deep linear depressions in the topography. An example of a major strike fault is the Agam Lake kiult, which strikes due west, from north of Manitouwadge lake to almost the west boundary of the map area, lust north of and roughly parallel to the belt of volcanic rocks. This fault is pre—ore in age, and is represented by a wide zone of graphitic schist, in places mineralized with pyrite and pyrrhotite. The magnitude and direction of 30 �movement along this break have not been determined. However, the fault appears to truncate a flumber of pre—ore, right—hand transverse faults, and at the same time, appears to be terminated by the north—south, post—ore, left—hand Fox Creek fault. At least three periods of movement are thus indicated. A possible fourth period of disturbance may be responsible for the fault that extends diagonally across the area from northwest to southeast. In regard to this fault, the offsets shown by the rock formations are of interest. In the northwest section of the area, the formations dip rather flatly to the southeast. Here the displacement was left— hand, or east side to the north. In the southeast section of the area, the formations dip about 650 to the northwest. Here the displacement was right—hand, or east side to the south. To the east of the Geco mine, the formations dip vertically. Here the formations have been traced across the fault to Wowun lake without any great apparent offset. Such anomalous conditions can be explained satisfactorily by assuming that the displacement along the fault was mainly vertical, and that the relative movement was up on the west side. South of Mose lake, a diabase dike was localized along this diagonal fault. But the diabase has been brecciated. Further, north of the Geco mine, the fault cuts and offsets two diabase dikes. In view of these facts and the simple vertical displacement indicated, it is thought that the two or more movements represented occurred in Late Precambrian time. Mineral Deposits All the important mineral deposits discovered to date are sulphide replacement bodies. Their locations are shown in Fig. 3. They strike and dip parallel to the formations that contain them, and have been found in or closely associated with either iron formation or a variety of sedimentary rock. A determination of the lead isotope ratios of a sample of golena, from one of the occurrences, by mass spectrometer is reyorted by J. T. Wilson of the University of Toronto to indicate an age of 2,600 + 120 million years. According to Wilson, the indicated age is close to that of leads found in the — Golden Manitou and Barvue deposits in Quebec and1 the gold ores of Timmins in Ontario. The lead from Manitouwadge lake, and those from the other deposits, are all much older than the Sudbury nickel—copper ores, which are believed to have been formed in Late Precambrian time. In view of this, it is reasonable to assume that the ore minerals were deposited during the period of granitic intrusion, and that they are of Late Archaean or Algoman age. Deposits in Iron Formation: Sulphide replacement deposits in iron formation have been found on the properties of Lun—Echo Gold Mines, Limited, about the nose of the Man itouwadge sync line, and Willroy Mines, Limited, on the south limb of the syncline. As mentioned previously, the iron formation is a banded rock, in which layers of quartz alternate with layers of amphibole schist, garnetiferous amphibole schist, or coarse—grained amphibolite. In the replacement dcwosits found in this rock, the metallic sulphides heal fractures in the quartz and occur as either masses or disseminqted crystals and grains replacing the minerals of the schist or amphibolite layers. Where massive replacement has occurred, the deposit is a strikingly banded one, in which layers of sulphides alternate with layers of mineralized quartz. On the other hand, where disseminated replacement has occurred, the sulphides appear to be localized along planes of foliation, which they accentuate. 3. Wilson, J0 T.,personal correspondence. 31 ��across widths ranging from 7 feet to over 15 feet. This section forms somewhat of a core in the ore body, and both to the north and to the south, the sulphide content of the host rock diminishes and th€ material drops rapidly below grade. The No. 2 zone has been traced for a length of 800 feet by surface drilling, and is reported to average 5.88 percent zinc and 1.71 ounces of silver per ton across an average width of 19.6 feet. Willroy No. 3 Zone The No. 3 zone lies 500 feet south of the shaft at the surface, and parallels the No. 2 zone closely in attitude. Again, near its west extremity, it curves sharply to assume a more northerly st.ike and a somewhat flatter dip. It is also very similar to the No. 2 zone in character. But here the principal sulphide is pyrrhotite rather than pyrite; chalcopyrite is present in significant amounts; arid galena is absent. The zone has been traced for a length of 1200 feet. It is reported to contain, to a vertical depth of 700 feet, 719,000 tons having an average grade of 1.27 percent copper, 10.3 percent zinc, and 1.5 ounces of silver per ton across an average width of 3l .5 feet. Deposits in Sedimentary Gneisses: Two types of ore bodies are found in the sediIentary gneisses, and may be classifiedas disseminated replacement deposits or as lode fissure deposits . Disseminated deposits occur on the property of Wiliroy Mines, Limited. Wiltroy No. I Zone The No. I ore zone on the Willroy propertg is also a body of disseminated ore. Near its west extremity it trends northwest and dips 45° — 50 N ,E. However, throughout the greater part of its length of 1900 feet, it strikes roughly east-west and dips 70° N. to vertical. The ore body ranges up to about 50 feet in width. It lies within the central portion of a horizon of highly sericitized, porphyroblastic quartz—feldspar—biotite gneiss, and consists of crystals and grains of metallic suiphides fisseminated throughout the host rock. The pyrite has no preferred orientation. But the chalcopyrite and pyrrhotite, as well as occasional stringers of quartz, tend to occur as individuals elongated parallel to the foliation of the gneiss. Because of this orientation, the chalcopyrite and pyrrhotite zi Iso tend to be concentrated in thin layers and streaks, with the result that, in drill cores, narrow sections rich in copper alternate with sections poor in copper. The sphalerite, in part at least, replaces the pyrrhotite. A feature of particular interest is the fact that the ore body is paralleled along ts north side by a band, about 15 feet in thickness, of white, crenulated quartz—sericite. This schist, unlike the less altered gneiss, is only sparingly mineralized and is extremely low grade. The Willroy No. I ore body is estimated to contain, to a vgrtical depth of 500 feet, 796,000 tons grading 1.5 percent copper, with low values in zinc and silver G11o Ore Body The Geco ore body is exposed about 600 feet south and 1800 feet east of the Willroy No. I zone, and from here extends eastward for a horizontal length of 2,650 feet. Like the Willroy No. I zone, 4. Bateman, Alan, M. "Economic Mineral Deposits," John Wiley & Sons, Inc., N.Y., p.111, l942. 5. Hooke, Eric, Chief Geologist, personal communication. 33 �it lies within the horizon of highly sericitized quartz—feldspar—biotite gneiss, which is bordered on the north by garnetiferous amphibole—biotite gneiss and biotite granite, and on the south by quartzite. It is a lode fissure rather than a simple disseminated replacement deposit. As shown in Fig. 4, it can be divided conveniently into three sections: the West, Central, and East. c7 (40 CENTR&.. Ii DIAI3ASE DISSEMINATED ORE MASSIVE ORE PEGMATITE, GRANITE N It FEET .. 400 - SERICITE SCHIST 800 IRON roRMAnow CAR.—AMPH.--øI. ONEISS SEDIMENTARY CNtDS Fig. 4. Surface plan showing generalized geology in the vicinity of the Geco ore body (modified after company plans). The West section of the ore body lies west of Fox Creek. It has a length of 1,200 feet at the surface, ranges up to 220 feet in thickness, and rakes to the east at about 40 degrees. In part it is in every respect similar to the Willroy No. I zone, and consists of highly sericitized gneiss mineralized with metallic sulphides, chiefly pyrite and chalcopyrite, and cut by occasional quartz stringers. But here the sulphides replace the host rock outward from a narrow, tabular core of massive ore made up of pyrite and sphalerite, with considerable pyrrhotite but relatively small amounts of chalcopyrite. This core occurs near the south wall of the ore body, within a few feet of the sericitized gneiss — quartzite contact. It decreases in width and tends to pinch out both to the west and with depth. To the east, the West section is cut off sharply by the Fox Creek fault, so that east of the creek, the extension of the ore body lies approximately 250 feet to the north. This extension, or Central section, extends eastward from the fault for a distance of 850 feet, to a point where it is truncated sharply by a zone of north—south diabase dikes. Near the surface the middle section has an average width of 58 feet. Like the West section, it consists of a core of massive sulphides, chiefly pyrite and sphalerite. This is enclosed by an envelope of iron, copper, and subordinate zinc sulphides disseminated throughout sericitized gneiss. But here the core is much wider than in the West section, and the envelope of disseminated material is narrower and, in places, below ore standards. Near the surface, the ore of the Central section is thus rich in zinc but poor in copper. With depth the core of the ore body decreases in width and tends to tongue out, whereas the bordering disseminated ore increases in width and grade. The net result of this is a gradual transition from a high—grade zinc and low—grade copper ore near the surface. to a high—grade copper and low—grade zinc ore at depth. This deep ore, rich in copper but containing low values in zinc, is identical in character to that found in the West section of the ore body, and there is little doubt that it represents the eastward extension of the West 34 �ction down the general rake of the ore body. As mentioned above, the Middle section of the ore body is truncated by a zone of north—south labase dikes. The East section of the ore body lies east of these dikes and extends for a horizontal ength of about 600 feet near the surface. It is identical to the central section in character, except ror three features: (I) both the core of massive sulphides and the envelope of disseminated ore are narrower and tongue out eastward; (2) the core of massive sulphides attains its maximum thickness of bout 50 feet at a depth below the surface of 700 feet, and pinches out upwards;. and (3) at the east margin of the zone of diabase dikes, the core is represented by massive pyrrhotite and pyrite, and sphalerite does not become an important constituent until a depth of about 500 feet is reached. The East section, at or close to the present erosion surface, thus represents the upper limit of the east— raking ore body. The Geco ore body has been tested by diamond drilling to a vertical depth of 1300 feet. To this depth, the three sections are estimated to contain 15,227,251 tons of ore having an average grade of 1.76 percent copper, 3.48 percent zinc, and 1.77 ounces of silver per ton6. Mineralization and Paragenesis The principal ore minerals in all the known deposits are chalcopyrite and sphalerite. Galena is often also present, and is particularly prominent in the Willroy No. 2 ore zone, but nowhere does it occur in sufficient quantity to be of economic importance. Silver is present in every deposit. It has not been recognized as such. Assaying of samples from the Geco ore body indicates that high values in copper are usually accompanied by high values in silver, and the thought has been expressed that the silver is present in solid solution in the chalcopyrite7. A qualitative spectrographic analysis of chalcopyrite from the Geco ore body indicated the presence of tin, which may also prove to be of economic importance8. Associated with ore minerals in all the deposits are quartz, in small veinlets, pyrite, and pyrrhotite. Small amounts of cubanite and marcasite have been found. The paragenesis, as given by Langford9 for the Geco occurrence, is as follows: (I) formation of pyrite; (2) fracturing and introduction of quartz; (3) formation of pyrrhotite; (4) formation of chalcopyrite, overlapped in part and followed by; (5) formation of sphalerite; and (6) formation of galena. The presence of ex—solution textures of sphalerite in chalcopyrite and of chalcopyrite in sphalerite indicates that the Geco ore minerals were formed at high temperatures, and that the deposit, according 6. The Northern Miner, April 5, p. 4!, .56 7. Langford, F. F., "Geology of the Geco Mine in the Iv¼znitouwadge Area, District of Thunder Bay, Ontario," Unpublished M. A. thesis, Queen's University, Kingston, Ontario, 1955. 8. Op. cit. 9. Op. cit. 35 �to LJndren's1° classification, is of the hypothermal typeU. This conclusion follows from the work of Buergerl2, who points out that chalcopyrite unmixes from sphalerite at temperatures of 350 to 4000 C, and from the work of Edwards13, who states that sphalerite unmixes from chalcopyrite at temperatures of 500 to 6000 C. Structural Controls of Ore Deposition One of the most interesting aspects of geological survey work is speculation as to the reasons why ore deposits are where they are after the ore deposits have been discovered and partly developed. Such speculation, in the hope that it may prove useful to further exploration, will constitute the balance of this paper. The structural controls of ore deposition in the Manitouwadge Lake area may be considered under two headings: malor controls, and minor controls. Major Controls The major controls over the deposition of the ores were the folded structures and certain pre—ore fa u Its. Folded Structures: In regard to the folded structures, dip determinations, and measurements of Iineatio made apparent by the parallel alignment of elongate biotite flakes and prismatic crystals of amphibole, indicate a regional plunge of the formations to the northeast. This plunge ranges from 15 — 25° in the west section of the area to about 40° in the east section. Of interest is the fact that the rake of all the known ore bodies or mineralized zones, and in the case of the Geco ore body, also of the zonal arrangement of sulphides, is in the same direction and at the same angle as the plunge of the formations. Pre—Ore Faults: One of the most interesting features of the area is the localization of the Geco and Willroy No. I ore bodies along a very persistent horizon of sericitized quartz—feldspar—biotite gneiss. At the Geco mine, this horizon is cut by north—south dikes of pegmatite, which are terminated abruptly by the massive suiphide core of the ore body and do not appear in expected positions on the other side of the core. This indicates that the massive suiphides were localized in a fault zone, and that this zone served as a channelway, along which the hydrothermal solutions, that effected the sericitization of the gneiss and the deposition of the ore minerals, actually migrated. At first consideration, it would appear that this fault zone, which is post—pegmatite in age, was developed after the formation of the major syncline. But the horizon of sericitized gneiss has been traced continuously across the area for a distance of 4 miles, and throughout this length it is everywhere conformable to the folded unaltered sediments enclosing it. Because of this, and because the alteration indicates the presence of a continuous channelway during the epoch of mineralization, it 0. Lindgren, W., "Mineral Deposits," McGraw—Hill Book Co. Inc., N.Y., 1933. II. Langford, F. F., op. cit. 12. Buerger, M. W., "Unmixing of Chalcopyrite from Sphalerite," Am. Mineral., Vol. 25, pp. 534— 538, 1934. 13. Edwards, A. B., "Textures of the Ore Minerals," Aust. Inst. of Mn. and Met., Melbourne, Australia, 1947. 36 �s concluded that the sericitized gneiss represents a bedding fault that was deformed with the other rock formations during the regional folding. The other ore bodies or mineralized zones in the area do not occur along persistent horizons of cltered rock. Nevertheless, it is thought that they also may have been localized along folded bedding :aults — faults that were of limited lateral extent and were formed as parallel structures merely sub— sdiary to the break" represented by the sericitized gneiss. In this regard, it is to be noted that mineralized zones containing pyrite and pyrrhotite have been found in numerous localities throughout the area, but that it is only close to the horizon of sericitized gneiss that such zones contain any significant amounts of copper, zinc, or silver. Minor Controls The minor features which are known to have exerted some influence in the localization of the ore codies are: (I) intrusive—sediments contacts; (2) local curves or bends in the formations; and (3) the oresence of flat—lying bodies of granite pegmatite. Intrusive—Sediments Contacts: Examination of Fig. 4 shows that the Geco ore body lies within sericitized gneiss, which iidordered to the north by biotite granite and by garnetiferous amphibole — biotite gneiss. Where the sericitized gneiss is bordered by the granite, the best widths and values in copper have been found. On the other hand, where it is bordered by the garnetiferous amphibole— biotite gneiss, both to the west and to the east, the widths and metallic content decrease, and even the sericitic alteration becomes weak. It would thus appear that the contact, between the granite and the sericitized gneiss, localized the structural adjustments that provided the open spaces necessary for the migration of the ore—forming fluids and the deposition of the metallic sulphides. A second example, illustrating the effect of intrusive—sediments contacts on the localization of ore, is found in the Willroy No. 3 zone. Here the mineralization lies in a band of iron formation. This iron formation, and the sulphide mineralization within it, have been traced for 2300 feet. But the zone only attains ore grade where, over a length of 1200 feet, the iron formation is bordered along its footwall aide by a narrow, sill-like body of pegmatite. Local Curves or Bends in the Formations: A second minor but nevertheless important control over the localization of the ore bodies was the presence of local curves or bends in the formations. As shown in Fig. 4, the formations in the vicinity of the Geco ore body strike roughly east—west for a considerable distance, and dip vertically to steeply south. Near the west boundary of the area represented, however, the horizon of sericitized gneiss assumes a strike of N. 550 W. and a dip of 650 to 750 N. E. The ore body occurs where the sericitized gneiss strikes east—west and has a vertical or near—vertical dip. Similar conditions are found on the Willroy property. Here there are three ore bodies, all of which trend roughly east—west, and all of which terminate westward at points where their respective host rocks curve sharply to assume northwest strikes and flatter dips. The reason for the localization of the four ore bodies, along the east—west portions of their favourable host rocks, close to points of deflection in attitude, is found at the Geco mine. It was mentioned previously that the massive sulphide core of the ore body is localized along a fault zone which truncates iiixfies of pegmatite. In the sericitized gneiss adfacent to the massive sulphides numerous drag folds have been mapped. These drag folds are of two types: one type is "Z" — shaped in plan and is compatible with thy major Manitouwadge syncline; the other type is "S' shaped in plan and hence is a "reverse"structure incompatible with the major fold. Such "reverse" — 37 �drag folds have been found only in the horizon of sericitized gneiss, and it is logical to assume that they are expressions of the movement which culminated in the post—pegmatite faulting. They plunge at about 400 E., and indicate that the block of ground north of the fault moved down and to the west. A relative displacement of this type would result in the development o'favourable open spaces along the steep—dipping portions of the fault zone. Thus, as pointed out by Newhouse, 14 if one portion of a fracture surface dips steeply, and the other portion has a lower angle of dip, and if the hanging wall moves relatively down, the hanging wall will ride on the flat—dipping portion as a supporting surface. This will separate the hanging wall from a footwall along the steeply—dipping portion of the fracture surface to form an opening. Presence of Flat—Lying Bodies of Pegmatite: The third minor control over the localization of the ore bodies in the area was the presence of small, flat—lying bodies of pegmatite extending across horizons of favourable host—rocks. At the Geco mine, the north—south pegmatites that are truncated by the massive sulphide core dip at flat angles, in places eastward, in other places westward. These pegmatites are typically massive, pink, unaltered varieties. But, within a foot or two of their contacts, they are somewhat sericitized, and display fractures healed by metallic sulphides. According to Walter Clarke, chief geologist of Geco Mines, Limited, the disseminated ore in the sericitized gneiss tends to improve in grade as the contacts of these flat—lying bodies are approached. Similar pre—ore pegmatites cut across the ore zone at the Willroy No. I ore body. As each of the two pegmatites are approached from below, an increase in the width and/or grade of the ore body is apparent. Because of this it is thought that the flat—lying pegrnatites served as relatively impermeable barriers, which inhibited the migration of the ore—forming fluids and thus effected sulphide deposition in the sericitized gneiss at or close to their contacts. Conclusions Exploration and development work at the various properties permits tentative acceptance of certain valuable conclusions about the mineralization in the area. These facts are as follows: ) The mineral deposits are of Archaean age and may be related genetically to the granitic rocks. (2) All the known mineral deposits are replacement deposits, either disseminated or lode fissure in character, and occur in either iron formation or sedimentary gneiss. (3) The mineral deposits were formed at high temperatures, and may be considered as representative of Lindgre&s hypothermal class. (4) The deposits are controlled in their attitudes by the major folded structures, and rake flatly eastward horizon close parallel to lineations. They lie within a pre—ore folded fault zone that is represented (5) in the field by a persistent parallel structures of sericitized quartz—oligoclase—biotite gneiss, or they lie within smaller, to the horizon of sericitized gneiss. (6) adjacent strike roughly east—west, and where those formations curve sharply to assume a northwest strike and All the important ore bodies are found where the formations to and east of places relatively flat dips to the north. Two ore bodies, the Geco and the Willroy No. 3, are localized along the contacts between (7) granite or pegmatite and their respective favourable host rocks. Newhouse, W. H. "Structural Feature Associated with Ore Deposits," in Ore Deposits as Related to Structural Features, Princeton University Press, Princeton, N. J., p. 17, 1942. 14. 38 �(8) In two cases, at the Geco mine and in the Wiliroy No. I ore body, flat bodies of pegmatite served as relatively impermeable barriers, which inhibited the migration of the ore—forming fluids and effected sulphide deposition in the host rock at or close to their contacts. It is of interest to note that in several localities in the area, the horizon of sericitized gneiss has been found to disappear beneath outcrops of flat—lying pegmatites. Such occur at west end of the Geco ore body, in the extreme northwest corner of the Willroy property, and again between the Nama Creek and Lun Echo properties. In each of these places favourable ore structures may exist. But it seems unlikely that sulphide bodies can be located beneath the pegmatites by geophysical methods. Rather, it is concluded that successful exploration will necessitate detailed geological mapping, to determine the approximate location and trend of the sericitized gneiss beneath the pegmatites, followed by expensive diamond drilling. 39 �THE BLIND RiVER, ONTARIO, URANIUM AREA* by S. M. Roscoe The development of a major uranium mining field near Blind River, about 100 miles east of Sault Ste. Marie, Ontario, has doubtless been watched with considerable attention by those connected with the mineral industry here in the Lake Superior region. This new mining district is very different from any other mining district in Canada. It is, in many respects, more like an oil field than a mining area. From a geologist's point of view this has had several interesting effects. Probably more than in older mining areas, the services of numerous well—trained geologists are recognized as indispensible not only in controlling exploration work but also in helping to maintain profitable production from known ore— bodies. Most of the mining geologists, coming from other mining areas, have had the stimulating experience of having to re—orient their thinking from an emphasis on structure to an emphasis on stratigraphy and on concepts of sedimentation. Interesting also is the keen interest workers in the area have in problems of genesis — that is: are the deposits syngenetic or epigenetic? An important byproduct of the Blind River discoveries is the promise of a wealth of new geological data pertaining to Huronicsn rocks in the region north of Lake Huron. The Blind River uranium deposits are in pyritic quartz—pebble conglomerate beds within and near the base of Huronian sedimentary rocks. They are very similar to the gold-uranium deposits of the Witwatersrand in South Africa. The first discovery of this type of uranium deposit was the Pronto, near the shore of Lake Huron about 10 miles east of Blind River. The uraniferous conglomerate at Pronto was found at the base of a sequence of quartzite and other sedimentary rocks which unconformably overlies granite and green— stone. This discovery triggered intensive prospecting activity throughout the region in 1953. The search was concentrated along the contact between Huronian and pre—Huronian rocks. A number of deposits similar to the Pronto were soon discovered in basal Huronian rocks in the Quirke Lake — Elliot Lake sector about 25 miles northeast of Blind River. All of the important uranium deposits discovered to date in the Blind River area (other than the Pronto deposit) are in this sector. Numerous other occurrences of radioactive conglomerate have been found in other parts of the region, but in most of these the radioactivity is due principally to thorium. Possibilities of finding uranium deposits in these other areas, however, cannot, by any means, be considered exhausted. General Geology In the Quirke Lake — Elliot Lake sector, the Huronian rocks are folded into an open syncline * Published by permission of the Acting Deputy Minister, Department of Mines and Technical Surveys, Ottawa. 40 �which plunges gently to the west. The belt of sedimentary rocks preserved within the syncline is about 9 miles wide and about 5,000 feet thick in the central part (Fig. l).* Pre-Huronian Rocks The pre—Huronian rocks, where overlain by Proterozoic formations, are principally greenstones invaded by granodiorite. These basement rocks are averlain with unquestionable unconformity by the Huronian sedimentary rocks. Immediately beneath the unconformity, in most places, the basement rocks are altered in a manner very suggestive of a weathering profile. The altered zones show gradations upwards from normal basement rocks into highly sericitic rocks which are interpreted as residual deposits, or paleosols formed prior to deposition of the Huronian sediments. This residuum is thickest — locally up to 50 Feet tkick — where it overlies granitic rocks. It seems probable that such deeply—weathered zones were extensive over the pre-Huronian surface and provided the source of detrital material for the basal Huronian sediments. Huronian Sedimentary Rocks The Huronian sedimentary rocks of the North Shore of Lake Huron region were divided by Collins (1925) into a lower, Bruce series and an upper series called the Cobalt series. The Bruce series was divided from bottom to top into: the Mississagi formation —mainly quartzite; the Bruce Boulder conglomerate; the Espanola formation — limestone and greywacke; and the Serpent quartzite formation. Numerous drill—holes have now provided much more detailed information on the succession in the Quirke Lake — Elliot Lake sector than was obtainable from the original surface mapping. Stratigraphic correlations are very important in exploration for uranium ore iii this area, so it seems very desirable that some of the rock-stratigraphic units be redefined in the light of these new data. It is proposed that the Huronian rocks be divided into groups on the basis of cyclic repetitions of boulder conglomerate layers throughout the sequence. The Mississagi unit is elevated from formational rank to group rank and its base is defined as the bottom of the lowermost boulder conglomerate. The Elliot group, below this boulder conglomerate, is subdivided into two formations, the Matinenda formation and the Nordic formation. (Table I). Matinenda Formation The Matinenda formation contains all of the uranium deposits of the area and will be described in some detail. It is not possible within the scope of this paper to describe other stratigraphic units. These are illustrated diagrammatically on the accompanying composite columnar section. The following general features shown on the diagram might be noted in passing: The succession is characterized by layers of boulder conglomerate, each overlain by fine—grained sedimentary rocks which are in turn overlain by coarse grained, clastic sedimentary rocks. Both the Elliot group and the Mississagi group thicken rapidly to the south and also show a pronounced decrease in grain size in this direction. Note also that the Mississagi group overlaps the Elliot group in the northern part of the area. Such * Unfortunately it is not possible to reproduce more of the author's maps in this publication. reader is referred to the bibliography. — Ed. The �['441J to may o 0 (;ucIbcry !r'ipL tee) some oinr rentLe (i) cc 1eweenawan pooke Grcnttio Iva roo 4. ruc, tnoluctc, Ii GriinLr Fniaoocoio S 10 'OR N 14. N 1 A V >< -7 -I ' < V .7 V C & - N > A L '7 - - -7 N -, 4 r- ., , N .3 074(1 L -' ., >r — N < >V '1 N- Lrc -7 I A 4- LnkC take L >4 4-7 4 ( 3 4- -4 -7 V 4- / /4. L .4. >1 -7< ,J .7 -, F -1 4.. <-7 V< > 4 - r A < (- 200 4- -77<4<1- A < I- ç 4- N N N- 4 + -4- -4- 4- 4 + + '-+ .4- -4 + + + 4- + 4 4 4 N 4 -4- -N + 4- 4. + .. + -4 -4 + + 4- 4- -4- + +c,l + + .4. 4 .4. •+ + + + + + + N N + + .4. 4 + + + + + + + + 4. + 4- -N -4 + 4- + - + + -4- - N 4 + -N L4 4. 4- -4- 4- + -f'4 cli -4 4 + ) -4 4- 4 -N 4- 4. + 4- 4- + + + 4 -4. + + -4-. + N + A 000,lrr1in000 -N 4 4 -4 + 4 + 4 + 4 -f -I- + +LN -4- 4- -4 + + 4- + + + 4 Group nt rrtdtorloltve .4. + + -4. liIJROR <N A F 1> N- N ' 3 3 L- 1 F' N J '< V LAKE N4,4 A 1 -4 <V OF mnt4morphio rooks. rooks. -'-Elliot - iflQ(l4O5 some yornper st-cniLe (4) 'I - 1< < 1- -i '7 .37 ) v >1F-44- 4-IA A L-< , 14- F' i Al 41 N 4 1 1A -4> N N V -4 V. Nt-'7 -- V 41 A, N -4 N N 'J >t1N),J and mntamOrphto _4. -. 4-1 7 1, j, AN <N < N 7N '7> -< Imonlitry, voloania, and Fq. sail OrmimOOtone, rmoat "Ituronicin' OrflnlL' tome - -7 <" 1> A 4- -< ) N V/N -, -' N l0O mtls L -4.4 j." -i -' f -1 V •1 N <N< v NORTE 7,<A AL- >L RE000N 4r N SCALE A - A ,j - 4- N ,.4r '.rL I<-7 4- N7 INL- I- A > THZ >L- < l'4 - —< > - >' 4V 'l 2-7 N -4 IN 'J-Iuronian" sedImentary, voloanic, ----*- N - 1- '> N-I N < <4 4V< <7 F' N RO0I(S ¶7> LNt) I<1 "4-74., < L- , SAIJLT STE. MARX] -7 -J DISTRIOUIO1 0 'HUROI4iAN" 4- -N 4- -N + -4. 4 4- ÷ 4- .4 4- + + 4. 4- + + 4- + 4. 4- 4 + .4. ÷ + + 4- • 4- + 4- + -N -f + + 4 �(A) . it 0 31 aNkDtN pnSau.CuIaN ouNce IZPAi1CLA MISSISSAQI QUIRSIE SERflNT COWO.ASIbA F.MATIaL PRJ UNCONFM1TY C QUNLO) ;RouI' caanmas 0) }'MOiMED )MICC.ATIJtE AND OLDtR NOIISNCIA!VN* g Qrtenatuaa as gentle Pairotol (granite ao& greenotone residuum on pre -Ituronlan erosion surface) PuIyeniutI balder conglomerate OligSnduttc (quautaptbb1.1 conglomerate qitartatte Quit uuarsu-graiurd 1e1dapaIc F.ldupsthft quartuliN, uubgrsynckr Oreywuckr-uMjatoa ci Ai-gILlit. sIIttoiN g)Ny*&)kD SAmsnan. I) H NDflS SouthH ELLIOT LAKE AREA STRATICRAP}IIC SEQUENCE AND FACIRS VARIATIONS. QUIRKE LAKE-ELLIOT LAKE A)DtAtnD QUIRKE LAKE AREA �overlaps towards the north of lower formations by succeedingly higher formations is characteristic of the Huronian succession throughout the region. The Matinenda formation is composed of coarse—grained, clastic rocks including: quartz grit, feldspathic quartzite, arkose, and quartz—pebble conglomerate. These rocks are poorly bedded and poorly sorted, for the most part. Torrential cross bedding, seen on all outcrops of the formation, shows dips which were originally southeast to east (prior to folding). The formation shows pronounced local variations in thickness as well as a general regional thickening from north to south (0 to 700 feet). These local variations in thickness are believed to reflect the original topography of the pre— Huronian surface. The thicker parts can thus be interpreted as representing filled valleys, while adiacent thinner portions overlie hills and ridges on the buried pre—Huronian surface. Isopach maps show these valleys and ridges to have a southeasterly trend. The formation is believed to have been of alluvial origin, deposited by streams which flowed in a southeasterly direction. The Matinenda formation is distinctly radioactive. The radioactivity, apparently due mainly to monazite and zircon, is highest in coarse—grained pyrite—bearing beds. Closely packed quartz—pebble conglomerate is particularly pyritic and radioactive, with the radioactivity due to disseminated high— grade uranium minerals — brannerite, uraninite and 'thucolite' — as well as due to thorium in the more ubiquitous monazite and zircon. The thickest, coarsest—grained, most closely packed and most uraniferous conglomerate beds are found in relatively thick parts of the formation — that is, within or overlying pre—Huronian "valleys". Uranium Deposits Two such "valley" structures contain most of the uranium ore deposits discovered to date in the area. One extends southeastward from the Algom—Quirke mine and contains ore deposits along a length of about 5 miles which include the Algom—Quirke deposit, the Consolidated Denison deposit, the Spanish American deposit, the Zenmac deposit, the Panel deposit, and the Can Met deposit. The other extends northwestward from Algom's Nordic mine and contains ore deposits along a known length of about 4 miles which include the Nordic deposit, the Lake Nordic deposit, the Milliken Lake deposit, and the Stanleigh deposit. Algom's two mines are approaching production with plants that will have a combined capacity of 6,000 tons per day. Denison is constructing a 5,700 ton plant; Can Met, a 2,500 ton plant. The other companies mentioned are either sinking shafts or have announced plans to sink. Pronto is in production with a plant rated at 1,250 tons per day capacity. Thicknesses of ore zones are about 10 feet, and individual ore sections up to 32 feet thick have been reported. The ore deposits most typically consist of interlayered beds, one to three feet thick, of quartz—pebble conglomerate, conglomeritic quartzite, and pebble—free quartzite. The selection of the sections of such conglomeritic zones which are to be mined must be carefully controlled by sampling. Some of the highly pyritic conglomerate layers contain several tenths of one per cent U308, and rare seams, a fraction of an inch thick, may contain up to several per cent U308. Conglomeritic quartzite contains less uranium than the highly pyritic conglomerate, and pebble—free quartzite contains only very small amounts of uranium. In places, however, such quartzite contains a very high uranium content associated with pyrite along seams which follow cross—bedding planes. The ratio of thorium to uranium varies widely. ln quartzite and pebbly quartzite it is about 3 to I. In most ore deposits it is less than to I. In general, pyrite content, uranium content and thorium content all show close relationships to sedimentary features but show no clear cut relationship to features such as folds, faults, or contacts of diabase dykes. Places have been discovered, however, where uranium values appear to cut across sedimentary contacts and where rocks, not normally very I 44 �radioactive, contain ore where they are in contact with rich conglomerate. Pyritic Quartz-pebble Conglomerate The ore conglomerate contains pebbles of quartz, a few chert and jasper pebbles, and, very rarely, pebbles of argillite, greenstone, and granite. Pebbles are from 1/4 inch to 2 inches in diameter, and fairly well sized within individual layers (Fig. 2). They are moderately rounded and, in the Fig. 2. Hand Specimens of Pyritized Conglomerate from, left to right; Pronto Uranium Mines, Ontario; Algom Uranium Mines, Ontario. 45 �richest conglomerates, are tightly packed. The matrix contains abundant grains of pyrite, poorly— sorted granules and silt—sized particles of quartz and feldspar, and small plates of muscovite, sericite, chlorite, and epidote. The poorly sorted matrix of the conglomerate was probably not greatly modified by diagenetic Secondary quartz is found at the rims of some quartz pebbles. Overgrowths are found on a few quartz and feldspar grains and a little carbonate is present in the matrix of some conglomerate samples. It is difficult, however, to distinguish between secondary minerals of authogenic origin and those related to later metamorphism and hydrothermal alteration. processes. The conglomerates and adjacent rocks have been markedly deformed, probably concomitantly with folding and thrust faulting in the Huronian rocks. The following effects of such deformation are observable in thin sections: undulatory extinction in quartz grains; fractures with displacements; rotation of grains; and comminution of matrix material. The crushed rocks have been re—healed by secondary quartz, mica, chlorite and other minerals. Serrated boundaries between grains and granular texture within pebbles are common. Much of the pyrite has clearly crystallized or has been recrystallized subsequently to the deformation. Some of the uranium mineralization is also post— deformation in age. Most of the uranium in the ore is within grains of an amorphous, or metamict, material. This material contains abundant inclusions of anatase and gives an X—ray powder diffraction pattern similar to that of anatase; after strong heating, it gives the pattern of brannerite — a uranium titanate — as well as an anatase pattern. This material is therefore referred to as 'brannerite', although it cannot be considered certain that it was ever in the form of crystalline brannerite. The brannerite' occurs as discrete rounded grains and also as irregular intergrowths with pyrite. Uraninute is abundant in some ores and is found as angular to subangular grains. Brecciated uraninite grains have been noted. Thucolite', a uraniferous hydrocarbon, is common along fractures in the ores and also in rocks a considerable distance away from ore conglomerate beds. Pitchblende has been reported. Monazite and zircon, abundant in most ore samples, occur as rounded grains of detrital origin. Radioactive epidote (possibly allanite) and radioactive titanite have also been noted. Marcasite occurs in place of pyrite in some ores. Pyrrhotite and chalcopyrite are common, particularly in conglomerate at the very base of the Matinenda formation. Magnetite has been reported associated with pyrite. Cobaltite has also been identified. Galena is common. Molybdenite is found along slip planes in adjacent country rocks. Sphalerite is commonly associated with thucolite and carbonate in veinlets. Trace amounts of gold, silver, chromium, nickel and vanadium are also present in the ores. Origin Our knowledge of these deposits is still far a theory of their genesis. credible too incomplete to allow any forceful advancement of nevertheless, to give a brief summary of the more It might be interesting, hypotheses of origin which have been advanced. The placerists suggest that the original quartz—pebble gravels contained hematite, ilmenite, magnetite, rutile, titanite, epidote, pyrite and other sulphides, monazite, zircon and many other heavy minerals, including uranium minerals (possibly 'brannerite and uraninite). Subsequent diagenetic and metamorphic processes effected a certain amount of solution, redistribution, and recrystallization of constituents with little change in bulk chemical composition or addition of new 46 �elements other than sulphur. Large quantities of the latter are, of course, required to convert iron oxides to pyrite. The most serious criticism raised against this theory is that uranium minerals, particularly uraninite, are very unstable under weathering conditions and could not possibly have survived to become important constituents of the gravels. The most resistant radioactive minerals, such as monazite, contain much more thorium than uranium. Such minerals are also the most abundant radioactive minerals in most granitic rocks, which most commonly have a thorium—uranium ratio of about 3 to I. If it be granted for the moment that it is unlikely that there were in the source area any large bodies of rock which contained resistant uranium minerals in greater abundance thati thorium minerals, then it seems unlikely that extensive placer deposits which contain more uranium than thorium could have been formed. It is necessary, therefore, to consider possible mechanisms whereby the conglomerates could become enriched in uranium relative to thorium. Hydrothermal solutons or ground water, for example, may have dissolved uranium from adjacent country rocks and re—precipitated it in conglomerate; thorium might, at the same time, have been removed from the conglomerate. The hydrothermalists, seizing with glee upon the fact that the placerists are forced to admit that huge quantities of sulphur must have been added to the conglomerates, suggest that the relatively minute quantities of uranium in the conglomerates were introduced in the same manner, probably at the same time and probably from some deep seated source, rather than from adjacent rocks or from surficial waters. This later hypothesis requires that the conglomerates were preferred exclusively to all other rocks and structures as hosts for the introduced uranium. Such a preference could be attributed only to a much greater permeability or much more dilatant condition of the conglomerates as compared to other rocks at the time of the postulated uranium mineralization. Prior to consolidation, the quartz—pebble gravel with its poorly-sorted matrix was probably not greatly more permeable than overlying and underlying sands. It is difficult to evaluate how the relative permeabilities of the two rock types might have been changed by diagenesis, by cataclastic deformation and by metamorphism. Most of our present knowledge of these uranium deposits is of a qualitative nature. Quantitativa data on mineralogy, chemical composition, structural relationships, ages of mineralization, and so on, may resolve the problem, but a consideration of the length of time that the same problem has been argued in South Africa would warn us against expecting a speedy solution to the problem of origin of the Blind River Uranium ores. Bibliography Abraham, E. M.: Geology of Parts of Long and Spragge Townships, Blind River Uranium Area, District of Algoma; Ont. Dept. Mines, P.R. 1953—2, 1953. Arnold, R. G.: A Preliminary Account of the Mineralogy and Genesis of the Uraniferous Conglomerates of Blind River, Ontario; M. A. Sc. Thesis, 1954, University of Toronto. (On file at Library, University of Toronto). Collins, W. H.: North Shore of Lake Huron; Geol. Surv. Can., Mem. 143, 1925. Hart, R. C.; Harper, H. G.; and Algom Field Staff: Uranium Deposits of the Quirke Lake Trough, Algoma District, Ontario; C.I.M.M. Bull. Vol. 48, No. 517, 1955, (pp. 260-265). Joubin, F. R.: Uranium Deposits of the Algoma District, Ontario; C.I.M. Trans., Vol LVII, 1954 (pp. 431-437). Traill, R. J.: A Preliminary Account of the Mineralogy of Radioactive Conglomerates in the Blind 47 �River Region, Ontario; Can. Mm. Jour., Apr. 1954. Discussion Dr. A. W. Jolliffe (Queens University, Kingston, Canada): I would like to comment very briefly on this paper. One thing that I think the speaker did not emphasize that is worthwhile stressing is that here is an unusual deposit with some hundreds of millions of tons worth something in excess of a billion dollars. That is not lust a pious hope; it has been blocked out and a great deal of the ore has already been sold. So here is one of the great deposits of all time and it was found by a geologist, Mr. Franc. R. Joubin. The staking that followed the initial find was entirely guided by a geological map prepared by the Geological Survey of Canada - Dr. Collins' original map of this area made in 1924. think that point is worth stating; perhaps Dr. Roscoe did not want to stress it because he is a member of the Geological Survey of Canada himself, and I know from talking with the people who are developing these mines how great a contribution they feel that geology in general, and the Geological Survey of Canada in particular, have made to the development of this amazing camp. I Dr. J. W. Gruner (University of Minnesota): If we could imagine that the Colorado Plateau were metamorphosed as the Bruce series is we might get something similar to the Bruce series and to the Blind River deposits but there would be certain differences which would be very marked in the Plateau. We have no thorium whatsoever and of course that is one reason why the Plateau deposits are easy to explore because thorium does not interfere with any of the radiometric counting. We would also have another difference — that would be the presence of organic—plant trash as they call it out there. This is fossil material which of course would not be present in the Bruce series. But one thing we would have that would correspond to the thucolite, except for the thorium, would be asphaltite. The largest deposits on the Plateau are associated with this supposedly oil—derived, asphaltic hard material which you call thucolite in Canada. The clastic nature of the brannerite which have seen in microsopic sections has been compared with the clastic grains of uraninite in the Witwatersrand. However that is the greatest objection, as you all know, to epigenetic hydrothermal origin of these deposits, if these clastic grains exist. If they are really clastic grains we must change our ideas of the climate of the Precambrian because uraninite is not stable, we are sure, under the present conditions of oxygen in the atmosphere. I Mr. Wm. Belobraidich (Oliver Iron Mining Division): I understand that airborne magnetics were flown over the area. Was there any significant correlation between the magnetics and the orebody itself? Dr. Roscoe: No, there was none whatsoever; even scintillation airborne surveys have not been outstandingly successful in the area. They in general simply show outcrop areas of the tv¼itinenda formation or other radioactive formations and the aerial—magnetic surveys show diabase dikes and gabbroic bodies in basement rocks. There has been some thought of attempting to trace basement structures by use of magnetic information with the view that the basement structures would have a bearing on the topography of the basement floor and one might be able to get some clues about drilling in that manner, but nothing successful has been done that I know of. 48 �MAGNETIC PROSPECTING FOR IRON ORES by W. George WahI Iron—rich minerals forming ore deposits can be detected by all of the commonly used geophysical techniques except those based on radioactive decay. If the necessary geophysical contrasts exist, iron ore deposits can be mapped by electromagnetic, resistivity and self—potential surveys. Gravity surveys have outlined non—magnetic ore bodies but magnetism is the natural field force most commonly measured in the geophysical prospecting for iron ores. In general it may be stated that either iron ore deposits or the iron formations from which the deposits are derived are magnetic. This is true of the deposits in Michigan, Minnesota, Labrador, Quebec, and Ontario, but not of the Steep Rock and Michipicoten, Ontario, and Wabana, Newfoundland districts. The increased competition for new iron ore deposits caused by the depletion of reserves has forced instrument modifications and changes in field procedures which would speed up the mapping of magnetic data. Interpretive techniques had to be devised which would satisfy the demand for a rapid appraisal of magnetic anomalies. The field and interpretative methods and instrument modificatbns which will be discussed encompass the whole range of magnetic instruments from the first geophysical tool, the compass, to the latest, the airborne magnetometer. The compass is being used more and more as a reconnaissance geophysical tool because of its portability and ease of operation. The type of compass commonly wned by the prospectors can be used to gather data on the direction of the horizontal component of the magnetic force. If sufficient care is used, the results obtained can map magnetic deposits in great detail. The least a compass survey can accomplish is to delimit the area for more involved surveys. The compass may be used as a geophysical tool by measuring the azimuth of a line at fixed intervals across the area to be mapped. Pacing along surveyed property boundaries, claim lines, or picket lines will give sufficient control for this type of mapping. The local magnetic deflection may be plotted by arrows pointing in the direction taken by the compass needle. Figure I shows the results obtained by measuring the azimuth of north—south claim lines at 200 foot stations across an iron formation. This illustration shows that traverse lines 1/4 mile apart will map an iron formation in sufficient detail to enable certain deductions to be made as to the location and size of the causitive body. In this particular case, the data show that the iron for— mation reaches its greatest width towards the east side of the area mapped. This survey showed that the formation had a large potential volume and minable width. Prospecting in the area outlined by this survey uncovered an iron formation of sufficient promise to warrant further work. The compass survey, besides delimiting the area to be covered by a magnetometer survey, also shows the direction which the traverse lines should take to yield the most informative results. 49 �The data obtained on a compass survey may be shown in another manner, lithe amount of deflection from regional magnetic north is computed and if a negative value is assigned to those de— flections which are east of regional magnetic north and a positive value to those deflections west of regional magnetic north, the data may be contoured. The contoured results will show approximately the location, length, and width of the causitive body. The depth may also be approximated. A line drawn along the crest of the positive and negative anomalies will mark the extreme outside limit of the magnetic deposit. These lines will also tend to define the length of the causitive body. The zone across which the greatest rate of change occurs marks the axis of the magnetic body and also gives an indication of the depth of burial. The dip needle is another reconnaissance geophysical tool which will return excellent results if properly used. The lack of control on the survey, misorientation and improper leveling are in direct relationship with the care exerted by the operator. It has been found that a spot bubble on the face of the instrument will be a great aid in orienting the dip needle in a strong magnetic field. It can be shown that if the needle is counter—balanced so as to come to rest in a position normal to the earth's magnetic field the instrument is much more sensitive to small changes in that field. The confusion of positive and negative values, which are actually at odds with the normal conception of up and down can be eliminated by reading zero when the north—seeking end of the needle points vertically up, 900 when horizontal and 1800 when pointing vertically down. A Schmidt—type magnetometer is by design a delicate instrument of great sensitivity but cumbersome to use. Magnetometers have been or are being designed which will speed up the mapping of the data in the field. The null type, torsion magnetometers which do not have to be oriented or leveled and which have a great range of values are a step in the right direction. A practical solution to the time—consuming practice of changing auxiliary magnets in the Schmidt type instruments is to increase the size and weight of the sensitivity screw so that the scale constant is increased to around 400 or 500 gammas per scale division. It has been observed that little information is lost by using such a large scale constant when the results have to be contoured in 5000 gamma intervals. A detailed interpretation of magnetometer results obtained on a closely controlled survey will describe the causitive body as to location, depth, length, width and approximate grade or susceptibility. This is time consuming but the results obtained are usually sufficient to enable a conclusion to be drawn as to the relative worth of the causitive body. The following interpretative techniques have been devised which will rate the relative significance of magnetic anomalies on a preliminary appraisal of the magnetic data. Location: The causitive body is directly below the peak of a magnetometer anomaly. Depth: The depth can be approximated by measuring the horizontal distance between points where isomagnetic lines of equal intensity are evenly spaced and closest together. Area: The size of the causitive body can be approximated by sketching a line which loins the points of zero curvature around the anomaly. Grade: The relative grade or susceptibility of a magnetic body can be determined by comparing the intensity per unit area of its anomaly with other anomalies of the same shape in the immediate area. A discussion of this technique together with illustrations is presented later on in this paper. 'I An airborne—magnetometer survey is the most rapid method by which large areas can be mapped. The unit cost is low and the accuracy of the data obtained on a well controlled survey is equal to that 50 �obtained by the most sensitive ground instruments. In Canada airborne-magnetometer maps are available at relatively low cost from several government agencies. These maps show the magnetic data as mapped at the flight elevation and along certain flight lines. The data are contoured and as a result the placement of isomagnetic lines between the flight lines is interpreted. This causes some of thediscrepenciesencountered when comparing the results of a ground survey with those found on an airborne map. It is mere chance that a flight line passes directly over the peak of an anomaly. During a field examination the area between flight lines on either side of the peak of the anomaly mapped should be investigated. In some areas the lack of identifiable ground control causes some errors in the plotting of data. It is therefore advisable to cover additional ground to insure the adequate mapping on the ground of the cause of the anomaly found by the airborne—magnetometer survey. No additional work such as drilling or test pitting should be based on the results of an airborne survey alone. When examining a magnetic trend on an airborne sheet it may be observed that the peak values are not constant. This may be caused by a differing tenor of magnetite along the strike of the formation, by thickening and thinning of the formation, by differences in depth of the burial of the formation, by different flight elevations on adjacent flight lines, or by combinations of any of the above. Any interpretation of airborne mangetometer data must be made with a realization that the intensity varies inversely as the square of the distance and that closely spaced anomalies on the ground may resolve into one anomaly at the flight elevation. All interpretative techniques apply equally as well to airborne data as they do to ground data. The intensity per unit area method of comparing anomalies is especially useful when examining an airborne magnetometer survey. This consists of recording the intensity of an anomaly and dividing by the surface area of the anomaly. Comparison should only be made between anomalies of the same shape and depth of burial. For example, in the vicinity of Marmora, Ontario there is a 7,000 gamma positive anomaly found over the magnetite deposit now being mined by Bethlehem Steel Company, (Fig. 2). Approximately 10 miles northeast of Marmora another 7,000 gamma anomaly is located whkh is caused by a basic intrusive carrying about 5% magnetite, (Fig. 3). The anomaly over the magnetite deposit has approximately 10 times the intensity per unit area of the other anomaly. It may be assumed that magnetite comprises 50% of the mass causing the Marmora anomaly. This approximates the average grade of iron (35%) as shown by drilling. Anomalies whose causitive bodies are at different depths of burial can be evaluated in a like It is assumed that the intensity varies inversely as the square of the distance. Figures 2 and 5 show the Marmora anomaly as mapped at 500 feet terrain clearance. Figure 4 shows the anomaly mapped at 5,000 feet terrain clearance. manner. The following formula can be applied: distance squared xintensity area Figure 2 (500)2 x 6,700 104 16,000,000 sq. ft. Figure 4 (5,000)2 x 140 = 70 S0,000,000sq. ft. 51 �FigvreZ (500)2 x-,l0O 70 14,500,000 sq. ft. The discrepency in the above results is caused by the inability of the airplane to duplicate the flight paths. The results are sufficient to show that the method has merit. In comparing anomalies by this method only those anomalies of similar shape should be compared. Great discrepancies can result if long linear anomalies are compared to circular anomalies. Differences are also great when linear anomalies trending north—south are compared to east—west trending anomalies. 52 �— :t. C ...iat:- r / 44i't • I. '*C - - 1¼ CG.S. ANOMALY p / 0 2 Fig. 2. Seven—thousand gamma anomaly Fig. I. Compass survey across iron formation. at Marmora, Ontario. 5000 14.0 C Fig. 4. Marmora, Ontario anomaly at 5,000 feet clearance. Fig. 3. Seven-thousand gamma anomaly ten miles northeast of Marmora, Ontario. 500' 4100 !. 7 dnotndlvat 53 �RELATIONSHIP OF GRAVITY TO GEOLOG1CAL STRUCTURE IN MICHIGAN'S UPPER PENINSULA by L. 0. Bacon Introduction Gravity measurements were begun in the Upper Peninsula in 1950 in an attempt to determine the relationship between gravity variations and known geological structure, the final purpose of the work being to increase our knowledge of major geologic structures which in the most part lie hidden beneath glacial drift in the western half of the peninsula or beneath the Paleozoic sediments of the eastern half of the peninsula. This paper is a composite of work carried out by the writer and that of four students who investigated selected areas as part of their graduate programs. The area which was covered is shown in plate I. area of about 17,000 square miles. The Upper Peninsula of Michigan comprises an Station density varied considerably, a total of 4000 stations being occupied; however, station density varied from approximately one per square mile in the Iron River mining district to as little as one per township in the eastern end of the peninsula. In almost all cases stations occupied were along existing roads which in some areas are not very plentiful Field Work The gravity measurements were made with a Worden geodetic instrument which has a very low instrumental drift rate. Probable error in determination of latitude of the stations was± 0.1 mile. The majority of the stations occupied were U. S. Geological Survey or U. S. Coast and Geodetic Survey bench marks or along Michigan highways where elevation control was better than ± 1 foot. In areas where few bench marks were available, elevations were obtained by altimeter, using a station microbarograph to monitor air pressure fluctuations. Elevations determined by altimeter have a probable error of ± 5 feet in much of the area. Some elevations determined in this manner may be in error by—I— 10 feet. Topographic corrections were made for a limited number of stations; and such effects at other stations probably do not exceed 0.2 or 0.3 milflgal, since the area is not rugged. Effects of curvature of the earth are of the order of 0.3 to 0.6 milligal, depending upon elevation of the station. indirect effects are essentially constant over the area covered. In view of the above probable error, it is believed that the precision of the reduced data is of the order of—i-- milligal. I 54 �'cv —'N \ - . k S: , DcvtItl#4 *IIU*4$. 4 - K . I-,- S*tV4 -:M194fl EC$U$W$W NE CWEEw*Wsi S IW11GIIIIM 1110$ flJfiIntIOIt * = StAte - MLCS 1= to Plate I. Gravity-geological map of Upper Michigan. All stations values are calculated relative to the pendulum station at Iron River1, having a Bouguer value of —5 milligals. Plate I shows the gravity data of the Upper Peninsula contoured at a 10 milligal interval with the 5 milligal contour indicated in part of the area. I. Numbers refer to bibliography at end of paper. 55 �Geology is taken from the Geologic Map of the Upper Peninsula of Michigan2 and is somewhat generalized for the purposes of portrayal. The Huronian iron formations are shown, not primarily because they in themselves are deemed so important for their contribution to the gravity picture but primarily as a marker horizon; it is quite obvious, however, that upper Huronian sediments in sync linal structures do produce positive Bouguer anomalies. Maior gravity anomalies occur in the Keweenaw Peninsula associated with the middle Keweenawan lava flows. Other anomalies in the western half of the peninsula are generally associated with Huronian synclinal structures. A broad regional gravity anomaly exists in the eastern half of the peninsula. On the Keweenaw Peninsula gravity values vary from —1—10 milligals along the north side of the peninsula to — 70 milligals about t6 miles to the southeast along the southeast side of the peninsula. The contact between the sandstones and the flows is a fault. This is a fairly steeply dipping reverse fault having a throw generally considered to be the order of a few thousands of feet. A conservative estimate, from calculations based upon the observed gravity data, is a throw of the order of 12,000 feet, using a density contrast of 0.48 between the Keweenawan flows (density 2.86) and the sandstone (density 2.38). The very large gravity anomaly of the order of 100 milligals is strikingly similar in appearance to the mid—continent gravity high through Wisconsin, Minnesota, Iowa and Kansas.3'4 At the western end of the Upper Peninsula the malor feature is still the anomaly associated with the Keweenawan flows. However in the northern portion of the area a gravity terrace occurs on the flank of the anomaly. This is in the Porcupine Mountain region and is associated with the acid intrusives, granites and felsites which invade the area. The Huronian iron formation in the western end of this area is the iron—producing Gogebic The Huronian sediments here do not give rise to any pronounced gravity effect, a fact which may be attributed in part to lack of sufficient gravity stations as well as the narrowness of the band of sediments, which dip steeply northward between the Keweenawan flows to the north and the Archean granites to the south. There is, however, a warping of the gravity contours produced by the flows to the north and the less dense Archean rocks to the south. range. The south central area is almost entirely underlain by Precambrian sediments. The Upper Huronian sediments which occur in synclines such as the Iron River—Crystal Falls district of the Menominee range produce positive gravity anomalies because of the density contrast of about 0.3 between the Upper Huronian sediments and the surrounding Pre—Cambrian greenstones. Calculations indicate that the sync line which comprises the Iron River—Crystal Falls district has a depth of the order of 6000 feet. The deepest mines in the area extend downward only about 2000 feet. To the west of this district occurs a gravity anomaly which is about of the same order of magnitude. In a paper by Wyble and the writer in l95l the probable presence of a Huronian sedimentary basin in this area similar to the one to the east was postulated. There are no outcrops in the area, and seismic refraction surveys have indicated that glacial drift is from 60 to 300 feet in thickness. Drilling on a magnetic anomaly at the south edge of the gravity anomaly in 1955 encountered an amphibolite.6 This may be responsible for the gravity anomaly, although the writer does not believe that the limited work done is adequate to discount the original postulation. The gravity anomaly associated with the Marquette Iron Range, which is a synclinal structure somewhat similar to that of the Iron River—Crystal Falls district, has a maximum of 12 milligals in a surrounding field of —20 milligals. Calculations of the depth of this basin gives a figure of the order 56 �of 8,000 feet. Between these two synclinal basins lies a dome—shaped structure roughly 15 by 20 miles in extent. This structure is called the Amasa Oval after a nearby village. The core of this structure is Archean granite which gives rise to a negative anomaly of approximately 10 milligals with respect to the surrounding area. The offset of the negative anomaly may well be only apparent, as there is an extensive area which has not a single gravity station in it. Contouring of the area was done on the basis of the data available. In general there are positive anomalies associated with the synclinal structures which contain the Upper Huronian sediments. The Menominee district shown to the south and east of the Iron River—Crystal Falls region does not produce any pronounced gravity effect. The beds here dip to the south, and their east—west trend is reflected in the warping of the gravity contours. Magnetic measurements have traced the east—west belt as far eastward as Escanaba on the shores of Lake Michigan where a gravity high of —11 milligals within a surrounding —35 milligals exists. Actually, this gravity high lies to the north of the eastward extension of the Menominee Range; the writer believes that it is due to either a synclinal basin containing Upper Huronian sediments or a topographic high on the Precambrian surface, which at Escanaba lies about 800 feet beneath the surface. The anomaly may be a combination of both the above possibilities. A few magnetic stations in the northeast corner of this gravity anomalous area outlined a magnetic anomaly of about 10,000 gammas. To the south of the Menominee Range the gravity values decrease rapidly and are probably due to the thickening of the Paleozoic sediments as well as to the presence of granitic basement. The gravity values in the eastern half of the Upper Peninsula are in the area covered by Paleozoic The maior gravitational anomaly is the one associated with the Marciuette iron formation and the broad gravity high extending to the southeast across most of the eastern half of the peninsula. sediments. A number of smaller local anomalies are evident either as closed contours or as warping of the gravity contours. These are evidently a reflection of either the structure or the topography of the Precambrian basement below the Paleozoics. The area is now undergoing active exploration by one of the mining companies. Returning to consideration of the broad southeast—trending gravity and magnetic anomaly, we observe that it practically disappears where the Paleozoics thin out to nothing, that is, where the Archean rocks crop out, which suggests that the negative values to the north and south are caused by thick accumulations of lighter sediments. As we go eastward, the anomaly increases in magnitude. The few exposures of Paleozoic rocks have dips generally towards Lake Michigan, except in the northern part where the rocks on the north side of the anomaly dip to the north toward Lake Superior. This fact seems to indicate that this anomaly may be a reflection of the ridge or dividing line between the two basins. This is supported in part by deep drilling in the eastern end of the peninsula. Farther to the east we observe primarily only the continuation of this anomaly, which seems to continue across the straits of Mackinac into lower Michigan where it probably merges with the gravity high extending nearly the lepgth of the Lower Peninsula. There is also a swing of the anomaly due northward, indicating that the positive anomaly extends perhaps across the eastern end of Lake 57 �Superior. This northward trend seems to tie in with some of the dense lavas exposed along the north and east shores of Lake Superior in Ontario. There is a definite possibility that it is a continuation of these lavas which produces the anomaly running down through the Lower Peninsula of Michigan. The anomaly through the eastern Upper Peninsula and down through the Lower Peninsula is strikingly similar to the mid—continent gravity high which extends from the western end of the Lake Superior basin down through Minnesota, Iowa, Nebraska and Kansas. This latter anomaly is considered to be caused by a basic rock within the basement complex. Conclusion We see that the gravitational picture can be very complex in the region where Precambrian rocks are near the surface. The dense iron—bearing sync linal formations produce positive gravity anomalies, and much information can be obtained about major structural features from gravity investigations. Bibliography I. Pendulum Gravity Data in the United States. U. S. Coast and Geodetic Survey, Spec. Pub. No. 244. 2. Martin, Helen M., "Geologic Map of the Northern Peninsula of Michigan." Publication 39, Geologic Series 33, 1936. 3. Black, W. A., "Study of the Marked Positive Anomaly in the Northern Mid—Continent Region of the United States." Presented at Geological Society of American Annual Meeting, November 9, 1955. 4. Thiel, Edward, "Relationship of Gravity Values in Lake Superior Region to Geologic Structure." University of Wisconsin, PH. D. Thesis, 1955. 5. Bacon, L. 0. and Wyble, D. 0., "Gravity Investigations in the Iron River — Crystal Falls Mining District of Michigan." Trans. AIME, Mining Engineering, pp. 973—979, October 1952. 6. Seymour, 0., personal communication. Discussion Dr. W. S. White (U. S. Geological Survey): If you were to complete your profile between Isle Roya land the Keweenaw Peninsula by extrapolation, do you think it would produce a gravity high or a gravity low? Mr. Bacon: I would expect the Bouguer gravity anomaly to be larger in magnitude; however there might be a trough near the center due to thickening of the Upper Keweenawan sediments. Dr. White: This large anomaly supports the contention as outlined in my paper on the source of the lavas and mineralizing solutions. Would not the apparent lack of such an anomaly near the eastern end of Lake Superior preclude the presence of Keweenawan lavas in this area? Mr. Bacon: Not necessarily. The indicated low gravity values in the eastern end of Lake Superior may be due primarily to the thickening of the Lake Superior sandstone. 58 �GEOLOGICAL FACTORS AFFECTING BENEFICIATION OF LAKE SUPER! OR IRON ORES by M. E. Volin The geologist finds it convenient to classify formations according to mineral constituents, origin, texture, color, and many other significant features. In evaluating his discoveries or expectations for discoveries towards reaching a decision on how far to pursue his exploration objectives, the geologist applies some general cut—off factor related to the economics of utilization of the ore minerals, be it grade, metallurgical response, or a combination of many such things. Thus he brings to bear an appreciation of the principal problems involved in converting his potential raw material into a marketable product. The mineral dressing engineer who receives the samples sent by the geologist is singularly interested in their response to his techniques of beneficiation methods. He assumes that the samples represent the average character of a mineraNzed body of significant size, and it is his objective to find an economic way to recover the minerals in a useful form. Some of the geological records may be helpful to him in guiding his first estimate of how the mineral dressing problems can be attacked; the degree of usefulness will depend on the geologist's understanding of the problems in applying the beneficiation processes. Our panel subject may seem somewhat of a departure from the theme of geological exploration, but in proposing this subject it was my hope that the discussions would emphasize some of the geological information about the Lake Superior iron formations that can be of interest to the mineral dressing engineer and would point out factors that the geologist can bring into clearer definition as a help in attacking the mineral dressing problems. Exploration is an initial and very important phase of building and maintaining mineral enterprises, but the successive phases in reaching production are a series of logical steps in overcoming interrelated problems. The best possibility of success is teamwork by people who are experts in their particular lines but are informed on all the phases, and the need for this kind of coordination is more apparent as the problems become increasingly complex. The changes that have taken place in iron ore mining in Minnesota set a pattern for this industry in the Lake Superior region. We have seen the production picture change from all direct—shipping ores to increasing tonnages of beneficiated ores from larger and more corrvpJex plants until today we have the first huge taconite plants. This same trend with some different characteristics is underway here in Michigan, and it is being hastened by the competition from premium grade imported ores. As the low—grade iron resources come more and more into the picture, it is evident that a greater degree of teamwork between geologists and mineral dressing engineers is needed to resolve the problems of utilization. Just as the geologist has developed classifications of the iron formations to aid his search for ore, the mineral dressing engineer needs classifications of the formations, or other resource segments, in terms of metallurgical response. The geologkt can provide a lot of information helpful in dealing with the mineral dressing problems. The need for this sort of approach was pointed out as long ago as 1933 by Dr. T. M. Broderick, then research professor at the Michigan College of Mining and Technology, in his AIME publication entitled "Application of Geology to Problems of Iron Ore 59 �Concentration. We have for speakers men who have worked on the many problems of the Lake Superior ron ores and have an appreciation of the complex character of the low—grade resources. Each has been closely associated with the particular phase of the subject he will present. Although our discussions will largely be concerned with the Michigan iron formations, we are fortunate in having two of our Canadian neighbors here to tell us about the problems of the siderite ores in their locality; their information should be helpful to us in appraising the possibilities of the Michigan siderites. Pane I GEOLOGICAL CHARACTERISTICS OF MICHIGAN IRON ORES AFFECTING BENEFICIATION by Alan T. Broderick (Abstract) The amenability of an iron—bearing rock to beneficiation by physical methods depends principally on its mineralogy and grain size. In the case of sedimentary iron formation, these features were determined by events in geological history which can be conveniently divided into three periods. During the sedimentation—diagenesis period the original mineralogy and texture were established in response to the sea bottom and pre—lithification environment. If the principal iron mineral were magnetite in coarse enough grains, the amenability of the rock to magnetic concentration was established then without any later geological process being necessary. If, on the other hand, the principal mineral were hematite rather than magnetite, the formation would not be workable today without the grain—coarsening effect of metamorphism because the fine grind necessary for liberation is too fine for the flotation process. In some very restricted areas the siderite in carbonate—facies iron formation is pure enough to be of possible interest as a source of sintering ore. Silicate—facies rocks, since the iron in them is chemically bound to silica, cannot be made to yield a desirable product by physical methods regardless of the grain size. The grains of pyrite in sulfide—facies rocks are too fine to be upgraded by known physical methods. During the metamorohism period, the iron minerals adjusted to the new environment by increasing in grain size and/or by forming new minerals. In centers of high—grade metamorphism (garnet zone and above) the hematite and magnetite in iron formation of the oxide fades were so increased in grain size that the rock was made amenable to beneficiation by flotation. Under intense metamorphism, silicate, carbonate, and locally oxide facies rocks alter to coarse grunerite and are therefore not treatable physically. There is no appreciable volume of sulfide—facies rock in high—grade metamorphic areas in Michigan. During the oxidation period, the hematite of the oxide facies rocks was not altered. Magnetite altered to martite. The carbonate—and—silicate—facies rocks, particularly in low—grade metamorphic areas, were profoundly altered. If the carbonate and silicate layers simply oxidized in place with little or no addition of iron, the result is a banded rock containing layers of earthy hematite and/or goethite which is not treatable by gravity or flotation methods. However, magnetic roasting may be applicable. If, on the other hand, iron moved during the oxidation period and locally enriched the 60 �iron layers sufficiently, the result is a rock made up of bands of hard, dense direct—shipping grade material alternating with lean cherty or argfllaceous layers. Some of this type of formation can be and is being treated by gravity methods in Michigan. Table I shows graphically the relationships between the products of these three periods of geologic history. In order of decreasing tonnage available in significant widths at ledge in Michigan, the geological types of iron formation are listed below. Where a beneficiation plant is in operation or has been contemplated, it is listed with its type. I. Oxidized/Low-grade metamorphic/Carbonate and silicate facies 2. Unoxidized/Low-grade metamorphic/Carbonate and silicate facies 3. Low-grade metamorphic/Oxide facies 4. Unoxidized/High-grade metamorphic/Silicate fades, silicated carbonate and oxide facies 5. High—grade metamorphic/Oxide facies Book Mine, Iron County Empire Mine, Marquette County Humboldt, Republic Mines, Marquette County Groveland Mine, Dickinson County 6. Unoxidized/Low—grade metamorphic/Sulfide fa c I e s 7. Oxidized/High—grade metamorphic/Silicate facies, silicated carbonate and oxide facies 61 Ohio Mine, Marquette County �Minerals resulting Minerals resulting from OXIDATION from Principal Mineral Minerals resulting in from Minerals resulting from METAMORPHISM *-SEDIMENTATION 3 METAMORPHISM 3 OXI DATION and (Biatite Lane & (Garnet Lane & Diagenesis Facies Below) Specularite E Specularite (3) Martite 4— Magnetite (3)* Abave) — Hematite -3 't-l—5i02—3 Specularite (S)t> Specularite Hem. & Lim. Grunerite —3 e Magnetite —3 Magnetite (5) — Martite Hem. & Lim. Grunerite -.3 '>-I-5i02 -3 * * Hem. & Lim. ())<Siderite (2) <— Siderite Hem. & Lim. (1)4—Silicates (2) 4 Silicates 3 Grunerite (4) -3 Martite Hem. & tim. e Pyrite -9 Pyrite & Pyrrh?3 Limanite Limanite E Pyrite (6) Grunerite (4) —3 Martite (7) Hem. & tim. (7)* * Existing & contemplated beneficiatian plants in Michigan Numbers shaw approximate order of decreasing volume available at ledge in Michigan. Table 62 1 �THE RELATIONSHIP OF DIAGENESIS, METAMORPHISM AND SECONI)ARY OXIDATION TO THE CONCENTRATING CHARACTERISTICS OF THE NEGAUNEE IRON-FORMATION OF THE MARQUETTE RANGE by G. J. Anderson and Tsu Ming Han Introduction Over the past few years all of the major mining companies in the Lake Superior District have been focusing a great deal of attention on methods and techniques to benefic late the large low—grade reserves of iron formation distributed in this area. The Cleveland-Cliffs Iron Company has conducted extensive research on the Negaunee Iron Formation of the Marquette Range, and as a result have three properties in operation and a fourth which will be developed within the next few years. We have found that microscopic studies have played an important part in this research and have contributed considerable information to the development of the low—grade ores. These studies reveal that the methods and degree of concentration are governed by the geological processes to which the primary iron formation was subjected. The purpose of this report is to discuss the various types of iron formation produced by these processes and their concentrating characteristics. There have been at least two major theories regarding the origin of the iron formation. The earlier of these proposed a single—facies theory which suggests that all the iron was deposited as iron carbonate. A recent theory by Dr. Harold James may be considered a multiple—facies theory in which he proposes primary sulfides, carbonates, silicates and oxides. We are not advocating any particular theory; however, according to the information we have derived from our studies, we feel that we are in position to make some suggestions. We have found that the iron in the iron formation was largely deposited as iron carbonate which has been completely re—crystallized. There are virtually no sulfides present on the Marquette Range, so we cannot consider this type. There are iron silicates present in large quantities, but we believe they have probably formed by diagenesis of the carbonate iron formation plus fine clay and/or fine clastics. This is suggested because the silicates are intimately associated with fine clastic sediments and the plates penetrate into carbonate grains and replace clastic materials. A large portion of the iron formation is in the form of magnetite chert which may be formed either by the diagenetic replacement of the carbonate iron formation or by the diagenetic recrystallization of the primary magnetite iron formation, if it is present as Dr. James has indicated. There has possibly been some primary hematite and magnetite deposited locally, but they are present in very minor quantities. The hematite is usually associated with clastics and occurs as submicroscopic plates or grains. The magnetite is usually associated with chert and carbonaceous materials and occurs as irregular sub—microscopic grains. In summary, the information that we have available suggests that the iron formation, to a large extent was primarily deposited in the form of iron carbonate with some clastics, followed by diagenetic 63 �and metamorphic processes, ond then subiected to secondary oxidation. The mineralogy and mineral grain disposition of several samples from the Marquette Range are described below exemplifying the various types of iron formation. Types of Negaunee Iron Formation A. Diagenetic Iron Formation — Direct Magnetic Separation Magnetite—chert with some carbonate 2. Magnetite—silicates with carbonate chert 3. Magnetite—silicates with clastics 4. Cherty magnesium-iron carbonate 1. B. Oxidized Iron Formation - Magnetic Oxide Conversion I. Martite—chert 2. Martite—clastics 3. Goethitic hematite—chert 4. Goethitic chert C. Metamorphic Iron Formation — Froth Flotation I. Specular—hematite—chert with or without sericite 2. Magnetite—chert with some chlorite and locally garnet 3. Grunerite wth chert magnetite or garnet General Description and Concentrating Characteristics of the Various Types of Iron Formation A. Diagenetic Iron Formation — Direct Magnetic Separation The metallurgical characteristics of this type of iron formation are governed by the magnetite content, magnetite size, and mineral association. I. Magnetite—Chert with some Carbonate — The results of our studies which included both microscopic and metallurgical testing have shown that this material has the most favorable concentrating characteristics. The reasons for this are the simple mineral composition, uniformity of grain size, and sharp boundaries between the magnetite and the chert, Fig. 1. 2. Magnetite—Silicates with Carbonate Chert — Our studies have shown that this material can be concentrated, but is not as favorable as No. I because of the presence of fine silicates and finer magnetite which necessitate longer grinding for liberation. The magnetite is more closely interlocked with the gangue minerals, Fig. 2. 3. Magnetite—Silicates with Clastics — In this material the magnetite is not uniform in size some being as coarse as —65 mesh and some as fine as a few microns, Fig. 3. As a result, this material is treatable, but yields a low percentage iron recovery with a high mineral loss in the tailings in comparison with No's I and 2, due to the loss of fines embedded in the matrix. 64 �4. Cherty Magnesium—Iron Carbonate — A large part or the total of the iron in this material is tied up in the form of carbonate, Fig 4. The magnetite can be liberated when present, but generally the percent iron recovery is extremely low and the iron loss in the tailings is great. B. Oxidized Iron Formation - Magnetic Oxide Conversion The metallurgical characteristics of this type of iron formation are governed by the degree of oxidation, particle size, mineral texture, and the mineralogy. 1. Martite—Chert — Microscopic and metallurgical studies have shown that this material appears to be the most favorable for concentration by magnetic oxide conversion because of uniform crystal size and sharp boundaries between the martite and chert, Fig. 5. 2. Martite—Clastics — Studies have shown that this material is moderately favorable and that the martite can be concentrated; however, a large part of the iron is tied up as hematite in the matrix of the clastics, Fig. 6. As a result, the percentage of iron recovery is comparatively low and the iron loss in the tailings high. 3 & 4. Goethitic Hematite—Chert and Goethitic Chert — Studies have shown that, atthe present time, this material is undesirable for beneficiating by magnetic oxide conversion. This is due to the irregular forms, the fineness, and softness of the mineral particles, Fig. 7. As a result, the concentrates always contain an appreciable amotnt of silica and there is a considerable iron loss in the tailings. A microscopic statistical sampling study on the —65, -1- 100 mesh portion of the oxidized iron formation samples from one of the Cleveland—Cliffs Iron Company drill holes has been conducted. The results are indicated in Plate I which reveals the concentrating characteristics of the materials in this particular hole. C. Metamorphic Iron Formation — Froth Flotation The metallurgical characteristics of this type of iron formation are related to the crystal size of the minerals and the mineral assemblage. I. Specular Hematite—Chert with Sericite — The specular hematite in this material occurs as fairly oriented plates ranging from as coarse as 48 mesh and as fine as a few microns, Fig. 8. This material is the most favorable for concentrating by froth flotation because of good liberation of the ore particles and the fact that a very high grade concentrate can be obtained by grinding to approximately —65 mesh. 2. Magnetite—Chert with some Chlorite — Because this material is coarse—grained, Fig. 9, it can be treated by standard flotation methods or magnetic separation, but at our operating properties, it is being treated only by flotation. 3. Gruneritic Rock — This rock varies from pure grunerite to magnetite—grunerite, and grunerite— chert, Fig. 10. Locally, garnet appears as one of the chief constituents. This material is not economically treatable at the present time, based on the magnetite content; and it is not favorable for flotation. A correlation has been made between the mineral assemblages of the metamorphic iron formation 65 �PLATE I 0 MATERIAl. CLASSIFIED %SILICA WI COlIC. I$T*_o GMlMIIII 20 40 OVE$SUNOEN Most Ot$ul*etL — P1$IR*$Lt — WIOESIAA$4E MOST 111025111*$LI — — MIGROSCOPC SAMPliNG p10 METALLURGICAL. CHARACTERISTICS OF THE OXIDIZED PdEGAUNEE IRON-FORMATION -10 - IS TYPE OF $ATERIAb IN SO ClIENT LOOM OMMIEO MRTIOZ QLWr = IS AO % FlIM GOSOEC MARQUETTE RANGE CHARACTER8TICS OP THE MATERIAL RTITE -GOETH. clIENT MAflOt cmci MM1UT. cWlIT SO MANTttt'CH(Rt 3$ II 3 $$(7$IO45$ 34 3 12 tOMTtFE -OlIERT II MRTLV OXIDiZED 11231491 cR011120 MARTITE I 32511 #400*) NETALLURMCAL RESUISS EXPECTED DESIR*OLE lOG 2O 140 77 45 N*2tITE -OIlER? 34 SI TI1t- 0N.-CH. 40 24 I3' I I NT-S1W GiL GOETNITE IS FINELY INTERL000EC SlIM CHERT I 3 I $ 15 INIQI$IVEL* OXIOIEED cR$L 5#MIID NANTITE (lOOM - 325W) MU MOST UNOE$AILE CC$*MU IE)PT MS MART 0* S MART QOCITIL 011 SANE AS l30-I4DEXCGPT IT CONTAINS *002 NEMAIIIC-CHERI I uiosio.st 110 3 4 MAWflTE IS FAIRLY COARSE - ONOLILD *440 INTENSIVELY OXIDIZED ISO I I SAME AS 140- 445 (20011 T 44011) MARTITE -ClIENT DESIRAILE : . 200 3 47 TWO 2*702112 SIZES OF MAFTITE 2) ft 1 2*0 lOOM TO 400 N 1 i - _jj *440 400 N * l-bO' E!CEt 11 cONTAINS (5IH4TE }-IE44SEP1 IT COIITAINS GOCYMITE 540 IU U 250 Il. *00 IS MARTITE - 3) 40 30 3 I00 NT: NJ Oc:I:ITITE 19101510454.1 $00 310 $40 IAIITSIT - ClIENT 2 IMMATITE -ClIENT ISO 14lITt -Q*fit 310 ILW*TUE-CHEWT 24 MARTITE 0112441 MIXED WITH HEMATITE ClIENT . 30 SI lO $0 101Th1T2 S SOIL I** 102 FINELY INTE0I.OCNETi WITH DENT 33 ILMAT1TE *440 WETIII?2 ARE F$IELY INTERLOCKED SlIM DLXI HEMATITE ClIENT *11(20 *1111 11*17171 ClIENT 36 33 23 42 MOST UIID€$1NAILE UNOESI090LE MOST 491IE$IA*SU 400 420 31 3) 21 45 24 6$ 3$ IIEMI*T1T( ClIENT MIXED WISH 00*912 20*1025 NARTITE OHIO? UIPE$I44*$LL 00*1)42 ORAIIIED .ARTIT$ CIIERT MIXED WITH NIIMTFTC 0*41*5 0CMLE NARTITE GNENT $ HEMATITE -ClIENT . • 440 400 2* IMMATITI -OW S - $oImlT1-aIlRT MMTITE—GNCRT 450 S 4EMAT1TE $ SOETINTE ARC NIT449!ELT 1111(0200200 51141 ClIENT MARTITE SIZE MIlLS FROM 15W TO 32$ N MOST LIMCEINSIU MOST OCIINULE �in one of The Cleveland—Cliffs Iron Company diamond drill holes and their actual metallurgical test results obtained from the Cleveland—Cliffs lron Company Research Laboratory. The correlation is diagrammatically illustrated in Plate 2. Conclusion ln reviewing the types of iron formation it may be concluded that the diagenesis and metamorphism are constructive processes of ore beneficiation while secondary oxidation is not a favorable process. NOTE: The term "chert" mentioned in this paper optically is a fine—grained to medium— grained quartz which was re—crystallized from chert by diagenetic and metamorphic processes to various degrees. PLATE CHARACTERISTICS CONCENTRATING OF THE METAMORPHIC %SILICA IN CONCENTRATE 0/ IRON CONTENT IN TAILING 10% I-FM 0 0 20% 10% fERBURDEN SERICITE SCHIST 0 100 r rz (I) C) 200 I- SPECULAR - HEMATITE - CHERT L&i Iii Li 2 — 300 r MAGNETITE -CHERT C- DIA BA SE I- LU MAGNETITE -GRUNERITE DIABASE C MAGNETITE -GRUNERITE DIAGRAM SHOWING THE MINERAL ASSEMBLAGES TO THE DISTRIBUTION OF SILICA AND IRON PRODUCED BY FLOTATION. 67 IN RELATION IN THE PRODUCTS 2 �41 '44 4 r Fig. I Fig. 2 - Magnetite-carbonate—silicate. l25x Polished Section. Magnetite, white; carbonate, light grey; silicate plates, grey; and pits black. — Magnetite—chert with some carbon— 125x. Polished Section. Magnetite, ate. white; chert, grey; carbonate, light grey; and pits, black. It ' N pa Fig. 3 - Magnetite—clastics. Polished Section. Magnetite, white; gangue (quartz, Fig. 4 — Cherty magnesium iron carbonate. 200x. Thin Section. Carbonate, granular chlorite, etc.) grey; and pits, black. grey; and chert, white. Fig. 5 - Martite—chert. 125x. Polished Section. Magnetite remnants, greyish white; martite, white; chert, grey; and pits, black. Fig. 6 — Martite—clastics, screen openings: —400 mesh. Polished Section. Magnetite remnants, light grey; martite and hematite, white; gangue, dark grey; and pits, black. 68 �p. ft fr. 4 0. S 0 ': , a a d;f2 A.ti 'P 1F Fig. 8 — Specular hematite—chert. 125x. Polished Section. Specular hematite, white; gangue, grey; and pits, black. Fig. 7 — Hematite—goethite—chert. 125x. Polished Section. Hematite, white; geothite, light grey; gangue, dark grey; and pits, black. •r p I -l p N :' ' Th A Fig. 9 — Magnetite—chert. 125x. Polished Section. Magnetite, light grey; martite, Fig. 10 — Grunerite—chert. 100x. Thin Section. Grunerite, grey; chert, white; and white; gangue, grey; and pits, black. magnetite, black. 69 �THE NATURE AND BENEFICIATING PROPERTIES BY MICHIPICOTEN SIDERITES PART I - DISTRIBUTION AND NATURE by A. M. Goodwin Distribution A principal iron formation of the Michipicoten district extends in faulted segments from the Helen Mine northeastward to the vicinity of the Algoma Central Railway, a total distance of II miles. From west to east the individual segments are, a) Helen — Victoria — Alexander — presently producing 1.4 million tons annually; b) Siderite Hill — presently being prepared for production; c) Lucy; d) Ruth; e) Josephine — a former producer of hematite ore; and f) Bartlett — representing a reserve of siderite ore, Plate 1. Structure The iron formation is situated on the south limb of an east—west trending sync line which, at the Helen Mine, rakes eastward at 60 to 70 degrees. The limb has been overturned. Thus, the formation dips southward yet tops are to the north. Northerly trending, vertical faults and flat thrust faults are common. Offsets on the vertical faults, which are generally east side to the north, range up to 2 miles and on the flat thrusts in the order of 200 feet. Stratigraphy at the Helen Mine The iron formation is enclosed in volcanic rocks. Basic volcanics typically overlie the iron formation and acid volcanics typically underlie it. Overlying basic volcanics The basic volcanics overlying the iron formation have the appearance of normal pillow andesite. Pillow structures are well preserved and consistently indicate tops to the north. The contact between basic volcanics and underlying iron formation is generally abrupt. Iron Formation The iron formation consists of the following ternary succession in descending order, Fig. 1. Top Bottom Banded chert member Pyrite member Siderite member Banded Chert Member: This member ranges in thickness from 200 to 1000 feet and averages 500 feet. it consists of thin—bedded chert interbanded with siderite, pyrite, and magnetite. Local zones of graphitic chert contain up to 14 percent carbon. In contrast to other Precambrian iron formation, jasper is negligible. 70 �r / c aanzr4Y SARI fI tLJC/7X' I ,tj • - • -— SIDERI'E HILl. 1 /7 atZLAKE ,Th //< DSTRtBkJTION OF HELEN-BARTLETT IRON FORMATION. Heron LEGENO: — J. scole:- 60 MiFes Ob4.QSEME. 1—0_EG-WRE fr*o VOCSSTIOJI1 see eti.c #oi.cn,ct ;t $CMI - P tUOI3MII$$ Plate I — Distribution of Helen—Bartlett Iron Formation. Pyrite Member: This member is consistently located at the contact between chert and siderite. It ranges from 10 to 50 feet thick and consists of mixed pyrite, siderite, and chert. The member increases in thickness and purity towards the west end of the range. Sulphur has a marked limiting effect on the sintering process as will be described later. Siderite Member: This member averages 200 feet thick within the limits of present mining. There are variations in thickness of considerable magnitude as a result of faulting and original thickening and thinning. The siderite, for the most part, is of massive, uniform structure. It contains variable siliceous impurities which are present either as, a) evenly disseminated grains and patches of chert, or b) relatively thick, uniform chert zones. One such zone in the Victoria mine, called the Central Silica zone, ranges in thickness from 10 to 60 feet. It is formed of relatively coarse grained, essentially structureless chert. A persistent zone of banded chert typically separates siderite from the underlying acid volcanics. It is 5 to 15 feet thick and is similar in appearance to the main banded chert member. It contains considerable amounts of argillaceous impurities. Two principal diabase dykes transect the ore body. The siderite adjacent to the dykes has been partly altered to magnetite. The zone of alteration ranges in thickness from 10 to 50 feet. Magnetite presents certain beneficiating problems as will be described later. 71 �4OE..LIZED GROSS-SECbON OF IRON FORMATION — AFItA COLLINS & QUIRKE — —BAS1C VOLCANICSr E"CO CHERT MEMBER ). —iRON FORMATlOi— PYRITE MEMBER MEMBIR -/ , 1 —Ac1D YOLC*NJCS'— 200 O Feet Fig. I — Idealized Cross—section of Iron Formation. Chemical Composition Table I illustrates the chemical composition of a) average siderite, b) siderite-magnetite complex ALGOMA ORE PROPERTIES, LIMITED Jamestown, Ontario A B C 5.26 0.82 3.40 6.56 AlO Fe 36.7 510 1.65 0.16 43.8 40.2 1.44 Mn 2.20 2.30 MgO CaO 6.31 6.67 3.10 S 1.74 3.88 0.79 Ignition Loss 25.32 10.22 2.44 0.20 22.9 29.20 A. Siderite ore. D.D.H.U-3-57; 960-970 ft. B. Siderite—magnetite ore alongside diabase C. dyke. D.D.H.U—3-56; 930—940 ft. Pyrite-bearing ore. D.D.HI 256; 680—690 ft. Table alongside 1 — Analyses diabase dykes, and c) pyrite—rich siderite. The table illustrates, I) the sintering action of 72 �diabase dykes, 2) the abundance of magnesium in the ore relative to calcium, 3) negligible aluminum, 4) the manganese content. The ore is essentially a self—fluxing, manganese—bearing iron carbonate. Wall—Rock Alteration in Underlying Volcanics The chemical and spectrographic characteristics of wall—rock alteration in the underlying volcanics are being investigated at present. Alteration consists essentially of the addition to the volcanics of iron, manganese, magnesium, sulphur and carbon dioxide, together with the removal of silica and calcium. The degree of alteration increases upwards through the underlying volcanics and is most intense in the 100 — foot interval below the iron formation. There are also lateral variations in intensity away from the area of the present mine working. Origin The available evidence indicates that the iron formation originated in a submarine, volcanic environment. Iron, manganese, sulphur, and carbon dioxide are considered to represent products of fractional crystallization which occurred toward the end of a volcanic cycle. Acid volcanics likewise represent end products of the same fractionation, hence their persistent stratigraphic location beneath the iron formation. The iron formation is considered to have formed at the chemical plane on the sea floor where ascending, acid groundwaters of volcanic origin came in contact with alkaline to neutral sea water. The broad, horizontal chemical plane separating these two contrasting chemical environments is considered to have resulted in formation of the ternary succession which is so characteristic of the iron formation. In this manner banded chert was deposited as a chemical sediment on the sea floor. Siderite and pyrite members formed largely by replacement of basal portions of the banded chert member; replacement was controlled by increasing pH and decreasing pressure as the sea-water environment was reached. 73 �THE NATURE AND BENEFICIATI NG PROPERTIES OF MICHIPICOTEN SI DERITES PART II — BENEFICIATING PROPERTIES by D. R. Dorrance Introduction At the Helen Mine, the ore is beneficiated by two processes, namely heavy—media separation and sintering. All the ore is sintered, but that part which will not make sinter grade is first put through the sink—float plant. The cut—off between sinter grade and sink—float grade is between 7.5 and 8.0 percent 5i02. The sink—float operation will be described first. Sink—Float Operation The sink—float operation consists of separating minerals of different specific gravities by immersing them in a medium of high specific gravity. Minerals having a higher specific gravity than the medium will sink and those of lesser gravity will float. Siderite has a specific gravity of 3.60 and the gangue has a specific gravity of 2.40 and 3.10. By using a gravity of 3.30 a separation is made of ore and gangue. The heavy media used consists of finely ground ferrosilicon suspended in water. The ferrosilicon has a dry specific gravity of 6.9 and contains approximately 15 percent silicon. Theorebroughtup from underground is minus 4 inches in size and is stocked on either low—sulphur or high—sulphur piles. The ore is further reduced to I 1/2 inches by a system of screens and crushers in the sink—float plant. It is then subjected to intensive washing in order to remove all fines. In the separators the gangue material floats to the top bath and discharges out the end through a chute. The sink material sinks to the bottom and is raked ahead by means of a spiral to the head of the separator where it discharges onto screens. The excess medium is drained off to a 20—foot thickener. The underflow from the thickener is pumped to a 48—inch Dings magnetic separator where the ferrosilicon is reclaimed. Specific gravity determinations are taken on the separator every half hour. The specific gravity is kept around 3.30. Samples of the feed, sink, float and sands are taken each shift. The plant handles both high and low sulphur ores and makes a good separation. The ores high in magnetite give the most trouble because the magnetic fines cannot be cleaned out of the ferrosilicon and they then lower the specific gravity. The maximum magnetite that can be handled is 15 percent. Ores in which silica and pyrite are intimately mixed present a problem since the relatively heavy pyrite causes siliceous rock to sink. 74 �Sintering Operation The sintering operation consists of roasting siderite in order to drive off carbon dioxide and induce oxidation, thereby producing a high grade sinter ore in a physical form suitable for furnace feed. Roasting is accomplished by putting crushed ore and coke on oil—fired sintering machines. Hiah ignition temperatures result in dissociation of siderite. The gases are withdrawn by forced air drafts. Ore is brought from the Helen Mine to the sintering plant by means of an aerial tramway 15,000 feet long and by railroad cars. The tram carries approximately 3,600 tons per day and the railroad about 2,500 tons per day. The ore is transported by a system of conveyors to crushers and screens to produce a 1/4—inch feed. The feed to the sintering machines is made up of a mixture of screened siderite ore and screened coke. Proportioning of the components is done at each individual sinter— ing machine. The operator controls the rate of flow from the bins to a pelletizer where water is added. Mixing of the feed must be done so that an intimate blendng of ore, coke and moisture is obtained; in addition, the mixing should be done so that the mixed feed is thoroughly aerated and is in such physical condition that maximum porosity is obtained. The mixed feed is fed to the machines through reciprocating swing chutes. The finished sinter is dumped over bar grizzlies into bins and thence to railway cars. Maximum permissible limits in the sinter are 5102— 11.20 percent; 5— 0.100 percent. In order to stay within these limits, the feed must not contain more than 7.90 percent 5i02 and 4.0 percent S. Considerable care must be exercised both in mining and beneficiating to remain within these limits. Discussion Mr. Volin: The information in all of these papers is very gratifying to me. To have this subject included in a purely geological symposium was somewhat of a concession but I think we can see that geology ties up with beneficiation processes and of course the two of them go together in order to achieve the final result of bringing a property into production. 75 �DiSTRIBUTION OF TRACE ELEMENTS IN SOIL FRACTIONS by D. H. Yardley Geochemical prospecting is a relatively new scientific tool in the search for hidden ore deposits. It is so new that more papers have been published in this field since 1951 than in all preceding years. An investigation of some aspects of geochemical exploration was begun near Ely, Minnesota in late 1953. The test area is near the Kawishiwi River along the basal contact of Duluth gabbro with Giant's Range granite, Fig. 1. Funds for the study have been provided by the Graduate School of the University of Minnesota and the Minnesota Institute of Research. Fig. I — Index map, and outline of the Duluth Gabbro (after Schwartz & Davidson). The primary object of the investigation to date has been to obtain data on the distribution of trace elements in glacial materials in northern Minnesota. It was felt that such data would demonstrate whether or not soil samples would reflect the presence of a known mineralized zone below glacial till and some idea might be gained regarding the pattern of distribution to be expected in soils with a 76 �similar climatic history and of similar origin. To date the study has concerned itself with data on the distribution of Cu and Ni in glacial soil, Summary of Geology The Duluth gabbro is one of the world's largest basic intrusives and has been defined as a lopolith (4)*. It intrudes rocks which range in age from Keewatin to middle Keweenawan. Within the test area the gabbro is in contact with granite except for short sections where the gabbro is in contact with remnants of iron formation. Sulphide mineralization occurs very near and parallel to the basal contact of the gabbro for a distance of several miles. Schwartz and Davidson (10) have described the geologic setting of the mineralization and roted that the sulphides occur at the base of the thickest part of the gabbro. The sulphides occur disseminated n all the silicates and also as small interstitial masses but are most abundant in the plagioclase. A few tiny veinlets of sulphide are present but these may be deuteric. The sulphides found include chalcopyrite, cubanite, pentlandite, pyrrhotite and minute amounts of bornite. The sulphides are repor'ed to be syngenetic (10, p. 702), (II). The ratio of Cu:Ni is about 4:1. This ratio of copper—nickel content is based on analyses of samples from various outcrops. The average of seven surface samples (10, p. 702) is 0.57% Cu and 0.13% Ni. The average of 29 grab and chip samples from about 12 outcrops was 0.59% Cu and 0.17% Ni. The average for 30 surface samples obtained from 20 different 40—acre tracts (II) is 8.72% Fe, 0.44% Cu and 0.11% Ni. The average content of the above 66 samples is 0.53% Cu and 0.14% Ni, a ratio of 3.8:1. Test Procedure The chromograph method (13), which was used for all tests, makes use of a reaction between the metal being tested for and special reagent paper to form a colored spot. The colored spot obtained is compared to colored spots prepared from samples of known metal content. The chromograph enables one to apply a fixed volume of test solution to a fixed area of reagent paper under a fixed suction head. The variable is the amount of metal present in the test solution. Sample Treatment The dried soil samples were screened, a 0.1 gram portion fused with 0.5 grams of potassium bisulphate flux, the fused product digested in 13% sodium citrate solution, diluted to 5 ml and filtered. The pH of the filtrate was then adjusted to >8.5 and 0.2 ml used in the chromograph for the Ni test. The pH of a portion of the remaining filtrate was adjusted to 4.5 and 0.2 ml used for the copper test. Demineralized water obtained from a Barnstead Bantam Demineralizer was used for diluting and for cleaning equipment. Reagents were purified with dithizone solution where necessary and procedures carefully standardized so that the only variable would be the heavy metal content of * Numbers refer to bibliography at the end of paper. 77 �the samples. When it was necessary to prepare new reagent paper, new standard color spots were prepared so that any variation in the strength of the reagent paper would tend to cancel in color spot comparisons. All standards were made up using blank soil from the test area. pH Discussion Repeat tests by chromographic analysis in the early stages of the investigation often failed to check. Quantitative variations of 50% and occasionally more were common. Nickel tests on slightly basic test solutions would sometimes be blank or very low and show a very definite color on a repeat run; less often erratic copper tests were encountered. A series of tests on known samples, and on made-up samples, was run for Ni and Cu for a range of pH values. These samples contained Ni, Cu, and Co ions known to be present in anomalous parts of the test area. Table I illustrates the intensity readings of one series of colorimetric spots on test solution containing 500 ppm of Ni, and 500 ppm of Cu. Table I Ni Cu pH. p.p.m. 0 75 3.0 3.0 500 500 200 4.0 4.2 4.5 4.8 5.4 6.2 6.7 7.0 7.2 7.5 8.8 500 500 p.p.m. 7.0 7.2 7.5 8.2 8.5 9.2 9.5 10. 300 400 400 425 425 II. 425 500 500 450 400 300 300 500 1500 2000 reproducible results can be obtained within the general accuracy limits of ± 30% for the method, over a pH range of about 8.5 to 11 for Ni and 3 to 5.5 for Cu. The results demonstrate that Table I also shows that for either metal tests run at a pH of 5.5 to 8.5 are not reliable. The high Cu readings at pH >7.2 can be explained by precipitation of Cu, Co, and Ni by rubeanic acid reagent in ammoniacal solution (13, p 3). The low readings at pH 5.4 to 7 are perhaps (2, p 79) at which cupric Cu tends to precipitate as hydroxide or basic salt dilute solutions. Leach (7) used this explanation in interpretation of hydrogeochemical tests for Cu near Butte, Montana. related to the pH of 5.3 from The tests demonstrate that the pH of the test solutions is very important and that a standard pH within the ranges given above should be used when testing field samples. This point, perhaps, has 78 �not received sufficient emphasis in the literature, although the chromographic procedure used by the Geochemical Section of the U. S. Geological Survey does adjust the pH to the desired range. Sampling Procedure Sampling was carried out along five north—south traverse lines across the gabbro—granite contact. Insofar as possible, samples were taken at 100 foot intervals. The surface soil samples were taken at an average depth of about one foot which was below the high—humus surface layer and into clean till. At some sampling points, samples were taken at each foot of depth down to bedrock in order to obtain data as to vertical distribution and distrhDution below swamps. An auger and a Swedish type peat sampler were used in sampling down through swamp materials; casing was used where necessary. A hand auger—drill was used in taking samples in till. Areal Distribution Contours and Profiles Plotting of Cu, Ni, and Co content in contour form (Fig. 2) shows that anomalous amounts of Fig. 2 — Total Cu, Ni, & Co, in glacial till — Ely District, Minnesota. these metal ions occur in till over and closely adiacent to mineralized areas of the gabbro. Contouring nickel content alone, or the copper content, outlines the same target area. Contours of the copper 79 �content provide a more distinct anomaly than nickel because of the higher copper concentration: The position of the northern boundary of the anomaly implies that the mineralization is parallel to but not quite at the base of the gabbro. This is confirmed by 3 Bureau of Mines drill holes (3). Distribution by Soil Size Testing of soil samples for any geochemical campaign involves a decision whether the sample should be screened, and if screened what soil fraction should be selected for testing. The glacial overburden in the area displays a wide range of particle size. For this reason it was necessary to select the soil fraction which most likely is representative of the true heavy—metal content. The finer soil fractions generally are to be preferred in soil sampling, because suiphides would tend to weather to finer size (6, p 530). Exceptions to this general rule do occur. Sergeev (12, p 46), comparing the tin, tungsten, and chromium contents of —1mm. fractions with 5mm. and coarser sizes in the part of the halo nearest the deposit states, "The content of the valuable element is approximately the same in both. In places, however, the coarser fraction contains somewhat more of the valuable element. Lean samples (a remote or the train part of the halo) have a lower content of the valuable element (down to zero) in the coarser fraction, although its concentration is stable in the finer fraction. It may be concluded that dispersion takes place chiefly at the expense of the finer materials. And also, "Remembering that halos of saline genesis are characterized by secondary compounds less directly related to the massive rock, the advantages of observing the halos in the fine deluvial fraction become evident. Such samples provide a reliable expression of the dispersion halo in its largest spatial development." Sergeev refers to elements which are resistant to chemical weathering and are dominantly residual in nature. Ground—up coarse fractions which contain one or more large pieces of ore mineral would test high in metal. However, even those elements which occur in resistant minerals conform to the general rule in the train part of a halo. A factor which also favors the selection of the fine soil fractons, in addition to the tendency of sulphides to weather to finer sizes, is the probability that transportation of heavy metals by capillary solutions may be important in the formation of some geochemical halos, and capillarity would be most effective in materials within the finer size ranges. Bischoff (1, p 58), provides some indirect support for this view, "Gravel and coarse sand on the contrary proved very unfavorable, probably because of rapid drainage," and "The depth of favorable overburden through which ground water would bring appreciable quantities of heavy metals to surface was surprising. The practical maximum overburden is now considered to be 30 to 50 feet for clay and 20 to 30 feet for fine sand." Bischoff also noted a blanketing or masking effect of sand and gravel ridges. Distribution in Soil Fractions The much greater number of soil particles in a unit weight of fine materials would be much more likely to include some particles of mechanically derived ore mineral than would the coarser fractions. The finer sizes also provide a much larger total surface area and so could absorb more metal ions from percolating soil solutions. Thus the finer materials would tend to "fix" relatively larger amounts of metal ions; we might say that they have a larger total adsorptive capacity and so would be much more 80 �likely than the coarse fractions to refrect the presence of anomalous concentrations of trace elements. Samples were sieved through a 9 mesh screen and some were sieved into three sizes, —1—9 mesh, —9+80 mesh, and —80 mesh. Stainless steel screens were used to avoid possible contamination. Tests on blank samples of cleaned St. Peter sand before and after screening showed no contamination from abrasion of the screen. The screens used were all Tyler screen scale. Table II compares the metal content of the +9 mesh and —80 mesh fractions from ten sample locations. The +9 mesh material was crushed in an agate mortar before fusion. Table II Nickel p.p.m. +9 mesh Copper p.p.m. -80 mesh +9 mesh -80 mesh 5 7 0 0 30 0 5 15 0 0 10 5 25 375 250 0 250 100 10 100 5 0 120 50 160 25 50 300 400 350 0 70 5 250 10 10 5 15 0 5 830 140 70 Approxrra'e percentage detected in +9 mesh fraction: (compared to -80 mesh fraction) 1977 Nickel = 8% Copper: 7% One can cor'clude that for all practical purposes the heavy metals do not occur in the +9 mesh soil size, at least for the concentration rangesNshown. Table Ill is a comparison of the nickel content of —9+80 mesh and —80 mesh soil fractions. Although the —9+80 fraction contains a distinctly lower proportion of nickel, about two thirds as much, the anomaly would not be missed by testing only the —9+80 mesh fraction. A comparison of the Ni content for 30 samples on a parallel traverse showed that the —9—1—80 fraction averaged 62% as high as the —80 fraction. Again the anomaly was obvious, using either soil size. It seems reasonable to conclude that a mixture of the two sizes (all the —9 mesh material) will give dependable results for field comparisons. The preceding figures show that for most field work the finer soil sizes are more indicative of geochemical anomalies. To confirm this view a study was made of samples known to contain appreciable quantitks of Cu and Ni. The samples were screened to six products and five chromographic analyses were made for Ni and five for Cu. Agreement of analytic results was best in the finer size samples. Fig. 4 illustrates the distribution; in each case the p.p.m. of metal is the arithmetic mean of five analyses. 81 �Table Ill Comparison of Nickel content of -80 mesh soil fraction and —9+80 mesh fraction. 100 foot sample spacing. Line 5 Nickel p.p.m. .948Q me -80 mesh 0 0 tO 20 0 0 0 10 0 0 300 250 300 400 500 300 75 100 350 400 100 150 70 150 400 700 75 2795 0 1865 1000 900 800 Copper 700 600 S z p400 / / Nickel 01 300 4, 200 0' , 100 0 +9 +32 +80 +150 +200 -.200 Nesh Soil Fraction Fig. 4 — Cu and Ni Distribution. Average of 4 samples, 5 tests per soil fraction for each sample. (Each point represents 20 determinations.) 82 �The notable feature is that there is an increase of metal content with decreasing soil size in the coarser materials, but for the —80 mesh and finer fractions there is no increase, but rather a roughly equivalent metal content. The only exception to the above trend was one sample of "rubble—like" material consisting of more than 50% of +32 mesh size. In this case the +9 mesh material tested substantially higher than the —9+32 size. The normal trend applied for the fractions smaller than 32 mesh. Certain general conclusions which may be drawn from the above tests are: 1. —9 mesh material would be satisfactory for most field work but samples of only —80 mesh material will give more reliable results. 2. Use of —80 mesh soil is to be preferred where anomalies of small magnitude might be expected. 3. The levelling off of metal content in the sizes smaller than —80 mesh shows that nothing is gained by any attempt to screen to a size finer than 80 mesh. 4. There is no general distribution relationship between metal content and available surface area of the finer particles of soil. This is significant in any consideration of the processes by which trace elements move and are fixed in soils. 5. Tests of distribution of metal in various soil sizes should be carried out as a preliminary guide in new sampling areas. A pertinent question is whether the 0.1 gms. of soil used in a test is representative of the several grams of soil in the field sample? Or, stating the problem another way, "Is it necessary to use any special methods of mixing to insure that the test portion is representative of the whole sample?" Repeat tests show that sample results can be reproduced within the limits of accuracy of the method without any formal mixing other than that inherent in screening. The accuracy is sufficiently high so that there appears to be no danger of not detecting an anomalous metal content through failure to mix the samples formally. In addition, the test sample is as representative of the field sample as the field sample is of its area of influence. Hawkes and Lakin (5, p. 291) compared ground and quartered bulk samples of 500 gms. with grab samples of 5 gms. and concluded that "there is no significant loss in accuracy of data by substituting grab samples for bulk samples" Scooping of Samples All samples tested in this investigation to date have been carefully weighed on an analytical balance. However, a volumetric scoop designed to provide about 0.1 gms. of soil adds to the speed and ease of field methods for testing soils. Use of a scoop is recommended by several authors and has been found to give satisfactory Held results. The variation in soil sample weight when a scoop is used rather than a balance has been considered by Huff (6, p 531). Huff found that the error caused by scooping ranges from 3 to 11 per cent and averages about 7 per cent in any one area. Table 4 is a comparison of scoop weights for soil samples from the Ely district. The variation of weight for scoops of a particular soil size is small and is well within the accuracy of the test method. However, there are significant weight differences between equal volumes of different soil fractions from the same sample, and also between the same soil fractions from separate areas. Although the study is not comprehensive the results do indicate that scooping samples can lead to 83 �TABLE 4 Weight, in Grams, of Sail Sample Fractions Measured by Using a Valumetric Scaap Na. of Mesh Samples jStd. Deviation Weight (grams) Max. 74in. 2 x Std. Deviation Mean Grams 3T Grams 2.3 0.006 5 % 4.6 -9 40 0.138 0.123 0.130 0.003 -9-1-80 40 .132 .115 .125 .005 4 .010 8 -80 40 .109 .095 .101 .005 5 .010 10 —9 40 0.169 0.145 0.158 0.006 3.8 0.012 7.6 —9-4-80 40 .151 .127 .138 .007 5.1 .014 10.2 -80 40 .130 .114 .120 .004 3.3 .008 6.6 2 rather large variatians in weight af sample with cansequent variations in camputed metal cantent. If a scaap is used far sample measurement ane shauld check the mean weight af the soil size fractian selected far the different sail types encauntered. Then if necessary a carrectian factar can be applied ta the camputed results. Anamalous metal cantents are aften sa much greater than backgraund content that a correction factor for scoop weights usually can be ignored in field work. However, where the anomalous content may be of small magnitude the possible error due to using a volumetric scoop could be significant. References 1. Bischoff, C. T., Testing for Copper and Zinc in Canadian Glacial Soils. T.P. 36761, Trans. A.I.M.E., ppS7-o1, 1954. 2. Britton, H. T. S., Hydrogen Ions. Chapman and Hall, Ltd., London, p 79, 1942. 3. Grosh, Pennington, Wasson and Cooke, Investigation of Copper—Nickel Mineralization in Kawishiwi River Area, Lake County, Minn., U.S. Bureau of Mines R.I. 5177, 1955. 4. Grout, F. F., The Lopolith, an igneous form exemplified by the Duluth gabbro, Am. Jour. of Sci. 46, pp 516—522, 1918. 5. iRvkes, H. E. and Lakin, H. W., Vestigial Zinc in Surface Residuum Associated with Primary Zinc Ore in East Tennessee. Econ. Geol. Vol 44, pp 286—295. 1949. 6. Huff, L. C., A Sensitive Field Test for Detecting Heavy Metals in Soil or Sediment. Econ. Geol., Vol. 46, pp 524-540, 1951. 7. Leach, P., Simple Chemical Tests to Aid Prospectors. Eng. and Mm. Jour., Vol. 148, No. 10, p 79, 1947. 84 �8. Lovering, 1. S., Huff, L. C., and Almond, H., Dispersion of Copper From the San Manuel Copper Deposit, Pinal County, Arizona. Econ. Geol. Vol. 45, pp 493-514, 1950. 9. Salmi, R., Prospecting for Bog—covered Ore by Means of Peat Investigations. Bull. De La Commission Geologique de Finlande, No. 169, 1955. 10. Schwartz, G. M. and Davidson, D. M., Geologic Setting of the Copper—Nickel Prospect in the Duluth Gabbro near Ely, Minnesota. T.P. 33461, Trans. A.I.M.E., pp 699—702, 1952. 11. Schwartz, G. M. and Harris, J. M., Notes on Field Work in the Copper—Nickel Prospect Area, Lake County, Minnesota. Minn. Geol. Surv. Summary Report No. 6, 1952. 12. Sergeev, E. A., Geochemical Method of Prospecting for Ore Deposits. Selected Russian Papers on Geochemical Prospecting for Ores. Translated by V. P. Sokoloff and H. E. Hawkes, U. S. Geological Survey, p 46, 1950. 13. Stevens, R. E. and Lakin, H. W., The chromograph, a New Analytical Tool for Laboratory and Field Use. U. S. Geological Survey Circ. 63, 1949. 85 �TRENDS IN GEOCHEMICAL EXPLORATION by H. E. Hawkes The art of mineral exploration is at the present time passing through a period of revolutionary development. In the brief ten years since the war, radically new techniques of appraising ground for the possibilities of buried ore deposits have not only been perfected but have demonstrated their effectiveness by contributing to the actual discovery of new deposits. Whereas in the past, mineral discovery almost invariably started with the work of the independent and often untrained prospector, the new methods now available make it possible for large, well-capitalized exploration companies to carry out their own programs of primary exploration. The result has been an acceleration in discovery rate comparable with the increase in discovery of petroleum reserves with the development of advanced geophysical methods in the two decades before the war. Two outstanding features characterize the coming—of—age of mineral exploration techniques. The most spectacular of these is the perfection of technical methods of mineral reconnaissance of large tracts of unexplored ground by observations from aircraft. The airborne magnetometer, first of the low—unit—cost reconnaissance methods, has been credited with the discovery of a substantial number of our new deposits of magnetic iron ore. Airborne radiometric techniques have been applied widely in exploration for uranium. More recently, airborne electromagnetic surveys have been effectively used in detecting electrical conductors, a few of which already have led to the discovery of large deposits of basemetal sulfides. Air photographs are now generally used as a guide in interpreting regional geologic structures that may make favorable conditions for the emplacement of ores. The outstanding characteristic of all airborne surveys is extremely low cost per unit area, even though the over—all cost of equipment and operation may seem higher than that of the more conventional methods. The other new development in mineral exploration is the diversify of exploration techniques that is now commonly brought to bear on each individual problem. Whereas conventional exploration has been guided primarily by outcrop search and geologic study, followed immediately by drilling, the tendency now is for independent appraisals of a tract of ground by several or many methods — geological, geophysical and geochemical — and the synthesis of the indications from all methods in the interpretation of the economic possibilities. Geochemical methods of mineral exploration are playing an important part in the evolution of our mineral exploration techniques. The purpose of this paper is to point out the kinds of contributions that can be made by geochemical techniques to exploration with special emphasis on application in the glaciated terranes of the Canadian Shield. A "geochemical" method of mineral exploration is a method based on mapping variation in the chemical composition of some naturally occurring material, and the interpretation of the resulting chemical pattern in terms of possible mineralization in the vicinity. The chemical elements measured are most commonly the ore metals themselves, present usually only in trace amounts; the material sampled may be rock soil, stream sediment or water, glacial deposits, or vegetation. 86 �Geochemical Reconnaissance Probably the oldest method of locating bedrock ore, other than by simple outcrop search, is the panning of stream gravels for resistant heavy minerals such as gold, and the tracing of the trail of increasing values upstream to the bedrock source. More recently the waters of streams have been sampled and analyzed for traces of metals as a method of determining the existence of metalliferous deposits upstream. A similar pattern can be traced by sampling sediments collected from stream channels for traces of "exchangeable" metal (metal that is in equilibrium with the water, and hence that can be dissolved in weak chemical reagents). In all these methods, one sample, properly chosen and properly analyzed, either mineralogically or chemically, will tell the prospector how much of a chance he has of finding an orebody in the area drained by the stream. These potentially are methods of mineral reconnaissance of very considerable power. Within the last three years, geochemical reconnaissance based on determinations of the exchangeable "heavy metal' (mainly zinc) content of stream sediments has been applied on a large scale to exploration in New Brunswick and the Gasps Peninsula of Quebec. This method has, or soon will be, described in detail H the literature (Bloom, 1955; Hawkes and Bloom, 1955 and in press). The present discussion, therefore, will be limited to a brief summary of the principles and operation of the method. Sampling cons!sts of collecting a number of small samples of stream sediment at sites selected on the basis of optimum coverage. Experience has shown that the chances of missing an important zinc— bearing deposit is relatively slight if samples are taken within two miles downstream from the deposit. Common practice is to collect four samples at each site, two from the sedimentary material in the active channel of the stream, and two from the flood plain within a few feet of the active channel. Samples should be collected in non—contaminating containers, such as aluminum tins or waterproof envelopes, and brought back to field headquarters for analysis. One or two ounces of sample is ordinarily adequate. Samples are prepared for analysis by drying and sieving to minus 80 mesh, and discarding the coarse fraction that does not pass through the sieve. Analysis is by a technique described by Bloom (1955), in which a standard volume of the sample is shaken with a cold aqueous solution of ammonium citrate to which is added a solution of the reagent dithizone in xylene or toluene. Exchangeable zinc, and to a lesser extent lead and copper, in the sample is dissolved in the aqueous citrate solution, and then reacts with the dithizone to give a color change that is quantitatively proportional to the amount of metal extracted. The xylene solution of zinc—dithizone is a brilliant red, in strong contrast to the green of the original dithizone solution. Where insufficient zinc is present to react with all the dithizone available, the resulting color is a mixture of green and red, the hue of which depends on the relative amounts of unreacted dithizone and the zinc—dithizone complex. By selecting one of these intermediate colors, such as gray, for a standard endpoint, it is possible to determine the quantity of zinc extracted from the sample by adding barely enough dithizone solution to the system to reach the gray endpoint, and then recording the total volume of dithizone solution added. This test requires only very simple equipment that can, if desired, be packed as a compact kit for field use. lnterpretation of the data is facilitated by plotting the values for exchangeable metal directly on a posting map. In the absence of significant concentrations of metallic mineralization in the drainage basin above a sample site, the sample will ordinarily contain less than 4 parts per million of exchangeable metal. Samples containing over 10 ppm exchangeable metal may be considered a promising 87 �indication, depending on the size of the stream and the general geologic environment. containing over 40 ppm are strongly anomalous. Samples Follow—up of the most promising indications is carried out most conveniently by carrying a portable chemical test kit, and making the tests on the spot without drying or sieving. The original sample site should be revisited, and freshly collected sediment tested again to make sure that the high values were not due to contamination or to a local source of metal of no significance. Then, the trail of increasing metal values should be followed upstream to determine as far as possible the source area. Sediment analysis for exchangeable metals apparently outlines the same geochemical patterns as water analysis. It has distinct advantages over the water analysis in that the analytical technique is much easier and more reliable, the metal content does not fluctuate with the weather, dry stream beds can be sampled, and samples can be stored for future reference. Both methods, of course, have many limitations. All they can tell is that an unusually rich source of metal exists in the area upstream or upslope from an anomalous metal indication in the stream. They rarely lead to the exact location of the source, which must be determined by some other method. They also do not tell whether the source is a high grade deposit, or a broad zone of disseminated metal of no economic value. They cannot obtain a response from a deposit that is not undergoing active oxidation and leaching, such as might occur beneath a lake or swamp. However, even though these methods may miss some deposits, and give strong indications from disseminations of no value, they provide the prospector with extremely valuable ore guides at a very low cost per area covered. Geochemical Methods in an Integrated Exploration Program Although geochemical reconnaissance has certain serious shortcomings and ambiguities, the data of airborne magnetic and electromagnetic surveys also are fraughtwith uncertainties in interpretation. Geological mapping, furthermore, can only point out areas where, by analogy with areas of known mineralization, ore ought to occur. In detailed work in areas of glacial cover, geochemical soil anomalies are commonly associated with bedrock ore; unfortunately, the anomalies are many times displaced for considerable distances downslope or down-glacier from the suboutcrop of the ore. Still more unfortunately, strong geochemical soil anomalies have been found and mapped in areas of no important mineralization, where the source is weakly disseminated metal scattered through a large volume of rock. Geophysical patterns in detailed work can be equally ambiguous, though in different ways. Geology again can only tell where the ore ought to be, not where it Is. Because of this complex of uncertainties, it has become common practice in Canadian exploration work to prepare a series of maps as transparent overlays, each one of which shows the targets indicated by one particular method. Then the localities where the greatest number of target areas overlap is considered for more detailed exploration. The purpose of the entire schedule is the narrowing down of target areas for the final and most expensive phase of exploration, the diamond drilling. The cost of one wasted drill hole could often pay for a very considerable amount of preliminary reconnaissance or detailed exploration work. Mention might be made of a few actual examples of such integrated exploration programs in the Bathurst District of New Brunswick: (I) Airborne electromagnetic surveys were used for primary reconnaissance; electromagnetic 88 �anomalies were checked on the ground by geochemical soil surveys; localities where both methods showed anomalies were drilled. (2) Primary reconnaissance was by airborne electromagnetic surveys; anomalies were checked on the ground by both geochemical soil surveys and gravity surveys; where both ground methods showed anomalies, the localities were drilled. (3) Primary reconnaissance was by geochemical stream sediment analysis; anomalous wreas were detailed with geochemical soil surveys and ground electromagnetic surveys; localities showing both electromagnetic and geochemical soil anomalies were drilled. (4) Areas for airborne electromagnetic surveys were selected on the basis of regional geochemical patterns indicated by stream sediment surveys; anomalies were checked on the ground by geophysical methods. Geological studies accompanied all of the above programs. It should be mentioned that a number of other exploration schedules have been successfully applied in the Bathurst District that did not include the use of geochemical methods. Future Trends in Geochemical Exploration Geochemical methods of exploration, like geophysical methods, are at the present time going through a period of rapid development in which new or improved methods are continually being developed and successfully applied. At the moment, there is no sign that this sharp upward trend is starting to level off. However, it is still possible to make a few guesses as to what the future may hold in store. There is every reason to suppose that methods of geochemical reconnaissance based on analysis of stream water or sediment for metals other than zinc can be developed. Particular mention might be made of copper, molybdenum, and uranium as being particularly hopeful. The sampling and analysis of sediments from the bottom of fresh—water lakes shows promise as a means of locating sources of metal in the surrounding country; this would be particularly attractive in the Canadian Shield where aircraft can land on lakes, and samples can be taken without beaching the plane. Studies of the fine-grained fraction of glacial till holds some promise as a method of appraising the possibility of mineralization up—glacier from the sample site. Additional experimental work on the movement of metals from a source in the bedrock up into transported cover such as glacial moraine may lead to more reliable interpretation of geochemical soil anomalies in glaciated terrane. The most important trend in geochemical exploration is a human one. More and more geologists are becoming familiar with geochemical methods of ore finding, and are learning what these methods can and cannot do. More than ever before, exploration geologists are able to view these new techniques in their proper perspective with respect to the other available tools, and can integrate them into well-balanced exploration schedules. References Bloom, Harold: A Field Method for the Determination of Citrate—soluble Heavy Metals in Soil and Alluvium: Econ. Geology, vol. 50, p. 533, 1955. Hawkes, H.E., and Bloom, Harold: Geologic Application of a Test for Citrate-soluble Metals in Alluvium; Science, vol. 122, No. 3158, p. 77, 1955. 89 �Hawkes, H. E., and Bloom, Harold: Heavy Metals in Stream Sediment as an Exploration Guide; Mining Engineering. (In press.) Discussion Dr. J. W. Gruner (University of Minnesota): Are there any interfering ions in this ion—exchange work? Dr. Hawkes: In the first place, it is well to remember that what you measure with the Bloom Test is the group ofelements thatreactwith the reagent, dithizone. The principal metal is zinc, but the group also includes copper, lead, cobalt, mercury, and platinum, etc. As for interferences, you run across samples on which the method will not work and where you never know exactly why. Such effects can result from excesses of iron and manganese which are known to interfere with the dithizone reaction. Mr. M. P. Walle (Minnesota Department of Convervation): Has any geobotanical work been done in New Brunswick? Dr. Hawkes: I thnk that only a very small amount of experimental geobotanical work has been done in New Brunswick. The reason that the geobotanical method has not been more widely used is that you can usually find the same patterns by soil sampling, and with much less effort than you can with plant sampling. Mr. Neil B. Ivory (University of Minnesota): Would geochemical methods be useful for detecting deposits under the lakes by dispersion of metals into the lake—bottom sediments or water? Dr. Hawkes: This question opens up a field that we know very little about. On the surface of it, yu would say "No", but yet the fact is that you do find strong anomalies in some lakes that must be due to mineralization lying beneath the lake—bottom sediments. There are two possible ways that this could come about: one is that metal—rich glacial material derived from the pre—glacial outcrop, is deposited around the lake, then leached by modern ground water and the extracted metal deposited in the lake bottom; the other explanation is that perhaps solution and migration actually do occur in the reducing environment under the lake even though we can visualize no mechanism whereby this could take place. That is not answering your question. I am sorry, I wish I could because I would like to know the answer myself. Dr. W. S. White (U. S. Geological Survey): What has been done with respect to water flowing into swamps and water flowing out of swamps? Dr. Hawkes: Undoubtedly swamps do have an effect similar to lakes in precipitating metal. This effect, however, is not as universal or striking as you would expect. Ordinarily, metal—rich waters will retain most of the metal content on their way through a swamp. You cannot say the same of lakes; you do find strong anomalies in waters going into the lakes, that are absent in the water draining the same lakes. My hunch is that the effect in the lakes is due to plankton that scavenge the metal and then die and collect at the bottom; you do not get this condition in swamp waters. Water that filters through the muck of swamps would at first undergo a change in composition but in the course of time the metal content of the muck would come up to an equilbrium value, and then nothing further would happen. One limnologist some years ago published an account of the variation in copper in a glacial lake in Connecticut: he found that the copper content was distributed in three ways — 90 �one was ionic copper, another copper in living organisms (plankton), and the third was copper in dead organic material. The limnologists have technical names for all of these. Depending upon the time of year, the weather, the sunshine, and the composition of water entering the lake, the ratios between these three kinds of copper varied tremendously. The content of ionic copper in the lake was much more a measure of the season than of the copper content of waters entering the lake. Incidentally, he found that the ionic copper content of the inlets went up by a factor of 10 in the middle faIl when the leaves were rotting. Dr. Gruner: Has any work been done on peat with respect to the concentration of heavy metals? Dr. Hawkes: Yes, there has. Empirical work has shown that peat does absorb just about every metal. The agricultural people are also concerned about this same problem as muck farms are very valuable for raising certain kinds of produce. While I can say that a lot has been done, I would not dare try to summarize it here. In general, muck serves as a trap for trace metals. There was one muck farm in New York State adjoining a zinc—bearing Silurian dolomite formation; the zinc leached from the surrounding rocks accumulated in the muck until in spots the dry weight of the muck was as much as 16% zinc oxide; some of the ashed samples contained nearly 100% zinc oxide. In reply to a question from the floor I would say that "heavy metals" refers to a group of minor elements that react with the reagent dithizone. This reagent is most sensitive for zinc which is also the metal that is most likely to be in the stream sediment in major quantities. In our work the only other metals that were present in sufficient quantities to give a positive response were copper and lead; excesses of copper over zinc can be distinguished by the different color of copper—dithizone complex. I am sure you realize that in most ore deposits, metals go together in characteristic groups. Thus if you have a nickel deposit you will probably find copper; if you have a silver deposit you will probably find lead and zinc. Hence even with a method that measures only copper, lead and zinc you can get an indication of the majority of ore types. There are, of course, a good many you may not be able to detect, as for example high—grade silver deposits, tungsten, columbium, tin, etc. Dr. Yardley: I wish to call attention to a paper on "Prospecting for Bog Covered Ore by Means of Peat Investigations" by Dr. Martti Salmi of Finlandt It presents some very interesting data in connection with peat and muck and the effect of humic acid on their fixing powers. Trace elements in these organic materials are multilplied by 7, 8 and as high as 20 times that of clay minerals; they are a very powerful fixative agent. We have done a little work in northern Minnesota on this and we do find anomalies at a depth of 3 or 4 feet, that is considering the vertical profile. The shape of these apparently reflects whether it is essentially a transported anomaly or a non—transported anomaly. That work has not gone very far yet, but there is a little information on these peats. Dr. Gruner: Dr. Yardley mentioned humic acid. Now there is some information on humic acid available from investigations that are being conducted by the Chemical Engineering Department of the University of Minnesota. I got hold of some of it the other day and I thought I would try to see whether I could absorb uranium with this pure stuff because peat absorbs uranium very rapidly. got a negative result with humic acid. I Dr. Dutton: One phase of geochemical prospecting that Dr. Hawkes did not mention is in drill holes. Would you tell us something about it, Dr. Hawkes? * Reference 9, p. 85. 91 �Dr. Hawkes: Several of the oil companies, one in particular that I know of, are using geochemical logs for stratigraphic correlations of their holes. They find that by analyzing for particular elements (1 am not sure which ones they are, but I think there are four that have been found useful) and plotting the values on vertical sections, they can get very good drill hole correlations just as you do with electric logs, gamma ray logs or other types of geophysical logs. They take very large numbers of samples and feed them through an instrument known as a quantometer or automatic spectrograph. The samples are poured in at one end, and the analytical data comes out on punched tape at the other end. Something like this might be helpful in the Iron Ranges of Lake Superior where you want to correlate, or even find out whether you have, a stratigraphic section in the sequence. Some work of this kind has, in fact, been done on titanium. Dr. Dutton: Dr. Hawkes refers to some work in the Cuyuna district in Minnesota. In this area the iron formation, which is primarily interbedded siderite and chert, or silicate and chert, lies between slates and siltstones. The question arose as to methods for distinguishing sediments that were younger than iron formation from those older than iron formation. In a bulletin of the Minnesota Geological Survey, resulting from a cooperative investigation of the Cuyuna by the Federal and the State surveys, several of 12 or 15 chemical analyses have an exceptionally high content of TiC2 for sediments; some of these analyses ran as high as 2%. The samples with high Ti02 were in what was presumed, on the basis of the mapping done in the mines, to be hanging—wall materials. Dr. M. Fleischer of the Geochemical and Petrology Branch in Washington was asked whether or not it was likely that the titanium content would be sufficiently persistent and sufficiently characteristic that it could be used for stratigraphic purposes. He replied that he did not know actually, but it so happened that some of the chemists in the Branch had just perfected a field test for titanium and they were interested in trying it. Two chemists came to the Cuyuna district and in three days made 75 determinations. The determinations can be made in 10 minutes from the time the sample is selected and the cost is 10 cents. In three days they were able to show that there was a very diagnostic split in the titania values for the iron formation, for the rocks below the iron formation, and the other rocks above. The iron formation was the lowest of all three — less than a 1/2%. The rocks below the iron formation were approximately 1 to 1 1/2%, and the rocks above the iron formation 2% or more than 2%. This has been a most useful tool in working in the Cuyuna district inasmuch as within the vicinity of the mines, the only exposures of bedrock are in the pits themselves. There has been much drilling but unfortunately most of it has been churn drilling so only cuttings are generally available. Mr. R. G. Schmidt of the U. S. Geological Survey has run thousands of titania determinations on cuttings and it has been a tremendous help to him in tracing out the stratigraphic sequence in areas between mines and from that the structure in the Cuyuna district. The general method of this field test for titanium was published in Economic Geology*. I think that other things of a similar nature might very well be used. The matter of trace elements for stratigraphic purposes is a tool of which as yet we do not recognize the full potentialities and it is simply a matter of trying to find techniques which are sufficiently perfected that they can be used readily in the field. An offshot of this titanium test came from one of the Oliver Mining Company's geologists and concerned the rapid determination of iron content in a sample. In the titantum test a reagent is added to put the iron into solution so that it does not mask the color by which the amount of Ti02 is determined. In a field test for iron the general procedure is similar, but this decolorizing reagent is omitted. The sample solution is diluted a proper amount in accordance with having calibrated a photographic light meter with chemically analyzed samples. The photographic light *Shapiro, Leonard, and Brannock, W. W.: A Field Method for the Determination of Titanium in Rocks, Econ. Geol. Vol. 48, No. 4, pp. 282-287, 1953. 92 �meter is then used to determine the amount of iron in the digested sample at the same dilution. is a quick, easy method for field determination of iron. A member: How accurate is that? Dr. Dutton: I would be inclined to say within W% accuracy but I am not sure. 93 This �APPLIED PHOTOGEOLOGY by W. Warren Longley (Ira nscription) In the beginning 1 should mention that Aero Service Corporation, Philadelphia, Pennsylvania, is sponsoring this talk, and affiliates of that company, Knox, Bergman and Shearer of Denver, Colorado, have assisted me in preparing some of my material. I wish to discuss the general field of Photogrammetry and procedure followed in the Denver office in interpreting photographs. Most people know the value of aerial photographs for geological purposes, but few are familiar with the detailed procedures from the photography through to the final geological report. 1 regard it as a serious matter that so few geologists recognize what can be accomplished in Photogeology. find this is true not only with the general public, but with my associates in the field of Geology as well; and it is particularly annoying that at times 1 am not able to convert my own students who are studying Photogeology. shall, therefore, mention some facts in order that you may recognize the many uses of aerial photographs, and then 1 want to discuss in detail the problems of photo-interpretation in the Canadian Shield. It should be pointed out that geological interpretation of aerial photographs in the Canadian Shield, including western Upper Michigan, is quite different from that in most sections of the oil areas of this country. I 1 In regard to photogrammetry, all branches of interpretation depend on the quality and character of the initial photographs, and for that reason we must have good coverage and good photos in our initial work. Insofar as the historical development of photography in geology is concerned, 1 believe that some of the early efforts were made in the Canadian Rockies where horizontal photographs were taken from one mountain peak to another and in that way some aid was given to geological mapping. As time progressed we find that our first true aerial photographs were taken during World War 1. Following that, the equipment and techniques developed during World War 1 were applied, and in the late twenties and early thirties extensive use was made of oblique photos. Oblique photos can still be used to a certain extent in aiding geological investigations, but they do not have the advantage of the verticals. My first work with vertical aerial photographs was in 1936. From that time on the quality of the photographs and the techniques have been improving. I should mention here that Aero Service Corporation has been among the pioneers in the field of aerial photography and photogrammetry. might make here a distinction usually recognized by geologists: photogrammetry is primarily the compilation of various kinds of maps as contrasted to geological interpretaion. Most geologists do not like the tedious work of photogrammetry — they prefer having maps prepared for them and then proceeding to the geological study. Aero Service Corporation works primarily in the photography and photogrammetry fields. In their organization they now employ over 800 people and conduct project in photogrammetry and photogeology throughout the free world. 1 94 �In photogramrnetry, there are several problems to be considered and one of most importance is that the ohotogaphs must beadaptedto the lob in mind. There are many varieties of photography, of lenses, cameras, and final pictures, and in all of these one cannot do a proper lob unless the proper photographs are available. For instance, if you want to make a planimetric map of a city, photographs taken with a long focal—length lens at considerable height would be most satisfactory. If you want to work on geological interpretation and wish vertical control, then you need photographs taken with a short local-length lens. The lens most frequently used in this country has a focal— length of six inches. The focal—length of the lens has an influence on the pictures, and one should know what lens is best for a particular job. Re con na i ssa n c e In general reconnaissance work one wants a rapid coverage of the ground. Photography will be used in studying only major ground features. For such general reconnaissance there are several things we can do, one of which is to take vertical photographs on a scale of about one to 60,000 or one to 70,000. Taking vertical photos at that scale means that the airplane must be fairly high. When I first started work in photography and photo—interpretation, such photographs would not have been possible because the planes could not fly high enough. Another thing one can now do for this general reconnaissance coverage is to use a so—called tn—met camera system in which three photographs are taken simultaneously — left, right, and along the axis of flight. In that way it is possible to get a wide coverage in a single flight that is quite satisfactory for reconnaissance work. Another system being used for a wide coverage is low oblique. This is at an angle of about 120 that is rectified to the vertical plane for study. Thus, in general reconnaissance there are several choices— the vertical photographs, of a scale around 60,000 or 70,000, the tn—met system, or the low obliques. Detailed Reconnaissance In so—called detailed reconnaissance a different problem presents itself. Detailed reconnaissance yields excellent photographs for geological study. In this work a common practice is to employ scales of around one to 20,000, possibly one to 40,000, or occasionally around one to 15,000. One to 15,000 represents roughly 4 inches to the mile. 0n a.photo of this scale, using a magnifying stereoscope, one should be able to see a log across a creek and to pick out individual trees and objects of that kind. Using a scale of one to 40,000, only the major structural features will appear. The photo—interpreter, therefore, must know the general situation, must know his objective, and know precisely what scales are most adaptable. Of course, it is the problem of the photo—expert to appraise any land area or any particular geological region and to advise what photographs will do the best lob toward the desired objective. Detailed reconnaissance can also be done by enlarging photos, such as one to 60,000, but direct photographs are much better. Detailed Surface Mapping Now we come to another stage — that of detailed surface mapping. Detailed surface mapping is used in many engineering projects and also around a mine or mining prolect. For instance, in mapping for petroleum, usually the project will deal with hundreds of square miles. In mine mapping it might be a matter of a few square miles, and for these we might be using scales down to one to 1,000. The problem involved here, with photographs on a scale of one to 1,000, is that the vertical control will require the use of some of the more complicated photogrammetric devices, such as the 95 �Kelsh Plotter, Multiplex, Autograph, or Planograph, but with suitable photographs and the proper equipment one can get very detailed maps. Also, with stereoscopic study there are many features that the trained photo-interpreter can recognize. It must be realized, of course, that photographs do not solve all the problems of geology. Geological field work must accompany the photo interpretation in order to obtain the best results. That is to say, geological problems not solved in the photographs must be solved in the field, and that again leads to the objective of the job. There are many photographic interpretation projects in which the interpreter never leaves his office. The interpretation may be excellent, but one might say that for the best quality map the geologist should do detailed field checking. The photographic interpretation is merely a means whereby a much better final map will be produced at a fraction of the cost of ground mapping. Films Many new developments in the past few years have served as aids to photogrammetry. Panchromatic film is now being used which has a much greater latitude than film available a few years ago. Interpretation can be much more specific from this film, and I suspect we will find many improvements in film over the next few years. Infra—red is another film which has been used extensively in aerial photography in recent years. Infra-red film has some very decided advantages, particularly in forest survey work in some sections of the country. The primary advantage is where one wants to make a distinction between deciduous trees and conifers. If one wants to recognize species, infra—red is not as satisfactory as panchromatic film. I want to emphasize that because in some sections of Canada the ability to distinguish between deciduous and coniferous trees is very significant in interpreting geology, and a sharp contrast is obtained by using infra—red. Infra—red is also important when working in swamp areas, because the ground moisture is more apparent when photographed with infra—red film than with other films. The branch which 1 believe is presently receiving the greatest research attention is color photography. Color film for the usual 9" x 9" photograph is several times more expensive than panchromatic film. In a newer development, attention is focused on 55 millimeter film, and most of you are familiar enough with color to know that because of the "grain" one can use much smaller negatives of color than of black and white for the same final quality of picture. Interest is generated here, for in studying many geological features with color, detail obtained cannot be matched by black-and-white photography. I believe, therefore, that color photography in Geology has a great future. Some places where color differentiation may have a particular advantage are around metal deposits, particularly those of hydrothermal origin. It might be said on theoretical grounds that there should be extensive rock alteration around hydrothermal deposits. An increase in certain metal constituents in the soil should be reflected in the vegetation. It is believed that the different soil conditions and different metal constituents have an influence on vegetation. It can be demonstrated that certain species oF vegetation do absorb greater amounts of certain metals than other species. An area of primary research now is related to the effect of unusual soil on the initiation of the growing season and on early or late ripening. Another very significant factor is autumn coloration. If any great strides along these lines are to be made, it must be recognized that photography must be done at very specific seasons, and we hope that we can make some very significant contributions along this line. 96 �Control Also to be considered is the control of aerial photography. Any one using vertical pictures taken many years ago undoubtedly has been annoyed by flight strips going apart and coming together and by all kinds of gaps and irregularities. Through the application of radar principles we have developed procedures whereby it is possible to control a flight line. In trackless country a flight line can be laid out by radar which the airplane can follow specifically to get complete coverage and avoid the weaving for which the pilot cannot be blamed. Adding some shoran principles, we can determine the instantaneous position of the airplane, and I believe at the present time with some of our procedures we can spot our airplane position within 25 feet, and the position of the photograph center within 75 feet. Thus, when necessary, not only can we fly very straight parallel lines, but we can determine the precise relative position of the individual photos. With this principle we have tremendous potentialities for precise mapping which, of course, can be used directly with our geological work. Magnetics In connection with geological interpretation, we have new additions in other branches. The airborne magnetometer has contributed very greatly to photo interpretation, and new electromagnetic airborne equipment promises a revolution in magnetic work. Involved with the electro—magnetic work is a wide range of possible applications. This airborne instrument work is lust now in its infancy, and I am sure that over the next few years we are going to find tremendous applications of it as an assistance in photo interpretation. Commercial Photogeological Evaluation Methods Although various applications of photogeologic evaluation are used in ground water geology, hard rock geology, soil analysis and general geology, the major percentage of photogeological evaluation conducted today is directed towards oil exploration. The following discussion, therefore, focuses upon the principal method used today in compilation of data from the stereoscopic examination of air photographs for purposes of oil exploration. Consulting geological firms that specialize in photogeological evaluation are not equipped to compile air photograph coverage. They depend upon commercial and governmental agencies such as Aero Service Corporation and the Commodity Stabilization Service as a source for air photograph coverage. These agencies also offer mosaic coverage. Initial Procedures A three—fold operation initiates a photogeologic evaluation: Geological research, indexing and filing, and base—map construction. Geological research is conducted throughout the project area. This research is aimed towards the compilation of all geological data available from the literature both as regards structural geology and stratigraphy. Inasmuch as the entire geological evaluation must be based upon criteria observable on air photographs, any aid in the way of published field data facilitates the photogeological evaluation. While research is being conducted, the air photographs, mosaics and other materials used in the analysis must be properly indexed and filed. This routine task is important for the smooth operation of a photogeological evaluallon. The third 97 �process, initiated at the inception of a project, is the construction of base maps and accrual of control data for subsequent use in the drafting processes intimate to the final photogeological map compilation. If aerial mosaics are not available from either governmental or commercial agencies, the photo— geological firm must be prepared to construct mosaics. Mosaic construction, initiated prior to the geologic interpretation of air photographs, must be completed prior to geological evaluation so that the photos used for mosaic construction can also be used for geological interpretation. Photogeologica I Evaluation Upon conclusion of research, indexing and filing, the photogeological interpretation of the air photos is commenced. This geological study, the most important phase of photogeological evaluation, consumes a majority of the total time expended. In an area of considerable size the photogeological evaluation proceeds on 15' quadrangle increments. Each IS' quadrangle is assigned to a geologist for photo interpretation. After the geologist annotates every other air photograph and ties the photogeological interpretations within flight lines as well as between flight lines, the annotated photographs are submitted to a second geologist who studies the area to ascertain validity of the initial geological interpretation. At the termination of this geological evaluation, all of the final map data, except for the land network and drainage, are shown on the air photographs. These data include structural geology, stratigraphy, and culture. Mosaic Posting The posting of mosaics is a common step between the annotation of the air photographs and compilation of geological data to a land network. Either semi—controlled or controlled mosaics at a scale of 1/48,000 or 1/63,360 are used in this process. Mosaic annotation is not made directly on the mosaic emulsion surface. Thin acetate overlays, affixed to each mosaic, receive the pencil annotations. This method has two direct advantages: one, the acetate has a uniform surface that is amenable to pencil annotation, and two, upon completion of the acetate annotation, a preliminary print can be made from the annotated acetate for an early examination of the photogeological results. Cartographic draftsmen transfer data shown on air photographs to aerial mosaics. At the completion of geological interpretation and mosaic annotation, a set of preliminary maps printed from the acetate overlays is available to the client. At this time a geological field check of the photo evaluation is conducted. The field check is not aimed towards making a field map out of the photogeological evaluation, but rather to confirm the stratigraphical identification of rock units as well as questionable structural interpretations. All field derived data are shown on the aerial photographs, the aerial mosaics and on the final maps. Drafting Procedures Where photogeological evaluations are used in oil exploration, it is mandatory to orient the geological data with respect to sections, townships and ranges. Hence, compilation of photogeo— logical maps is inseparably related to land network identification. During the geological evaluation of air photographs, section tine fences and roads as well as prominent cultural detail are identified, and these control data are recorded on the pictures and 98 �annotated on the mosaics. A fair density of control is, therefore, available for orienting geological patterns with respect to the land network when the drafting stage is approached. If control data are scarce, various literature is used to further control identification. This literature includes topographical sheets, General Land Office plats, County Highway planning maps, and township plats. If mosaic construction is of average quality, an imperial linen base map tracing is placed over the annotated mosaic, and geological data are traced on the imperial linen in ink. The control established prior to drafting is used to orient the base map over the annotated acetate. After the map is completely drafted in ink, a geological and cultural legend and title are affixed thereto. The final map is colored with printer's ink and prepared for submittal. A photogeological report that sets forth the salient features of the evaluation plus conclusions in regard to oil exploration is prepared to accompany the final photogeological map. The Canadian Shield I will now go on to the next stage, that of particular applications of photogeology to the Canadian Shield. In oil areas one usually finds erosion in a satisfactory stage; the most ideal circumstance for photogeology is the mature stage of the erosion cycle, together with arid conditions. In the Canadian Shield there is a general cover of glacial till. Combined with this in many areas is a heavy timber cover. Consequently, conditions for photo interpretation in the Canadian Shield are somewhat undesirable, but there are many things that can be done. Insofar as metal deposits are concerned, we recognize a relationship between these deposits and certain kinds of igneous rocks; we also recogifize the relationship between metal deposits and fault and shear zones. This means that if we can make some distinction between rock types and detect fault and shear zones, we have made a contribution toward the ultimate goal in hard—rock geology of finding a mineral deposit. Another situation I should mention is the great scarcity of outcrops. When we start our photo— interpretation, therefore, we have to rely on slight relief and on drainage. On the photographs the only things we have are color tones and textures. Using stereo photos, the primary features to be searched for are linear structures on the upland areas, linear segments in streams, and also any linear distribution of the vegetation, Steeply dipping faults and shear zones have a rather linear expression, while low—angle faults do not have a true linear expression and will be more curved. In regard to vegetation, it is possible by careful analysis to recognize whether there is a deep or thin covering of soil; a thin one is helpful at times. If all one can do is pick out shear zones, why not pick them out on the ground and save trouble? I might point out one example on which I worked: I knew that there should be a strong fault zone going through a certain area, and I knew within a mile where it should be. When I first went to the field, did not have air photographs, and I searched that place back and forth for over two weeks trying to pick up the fault zone which I knew should be there. On the ground I could not find it because of till, low relief, and timber. finally got the photographs and within five minutes of studying them I was able to pick up the fault zone; there could be no question of its location, and one could trace it through the area. The point that I want to bring I I out is that many features can be seen and traced on the photographs that cannot be seen on the ground. In Precambrian areas careful topographical representation is significant because slight changes can mean a change in rock type. Of prime importance in Precambrian mapping for mineral deposits is complete delineation of sedimentary belts and lava belts, and their relationship to the surrounding igneous masses; minor changes in topography may show up these characteristics. Of course, detailed topographical expression can be worked out only with instruments such as the Kelsch Plotter, but even form—line sketching or contour—line sketching can be a tremendous help in presenting geological 99 �features. Another significant feature is the drainage. In initial geological work a very detailed of all streams is helpful, because even though till covers the bed rock, the stream distribution and the stream pattern may be significant in interpretation. plotting In the Precambrian areas such as I have worked on, the field checking procedures are far more extensive than in ordinary petroleum work. This means that it is necessary to have a photo interpreter in the field with a crew for ground checking and with some liaison between field crew and office men, the latter working with instruments that could not be carried out in the field, e.g., the Kelsch Plotter. plotting devices that Itis proved its accuracy and simplicity and is regarded as one of the more significant of the instruments in geological work. The Kelsch Plotter is one of the years in recent In regard to Canadian work, in summary and conclusion, I can just say that it is a difficult lob; many geologists express the opinion that the details of geology cannot be worked out from photographs. It is my opinion that a tremendous contribution can be made by photography, and at the present time with the use of the airborne magnetometer, we have an additional field. Recently I was rechecking one of my field lobs after airborne magnetic work had been done, and in several places where I was still in doubt after detailed photo study and field checking, I was able to settle the problems without question from the results of the airborne magnetic work. By combining airborne magnetometer work with photography, we are in a position to get a rather detailed map —- one from which we can select the more favorable areas for subsequent exploration. I believe that the application of these procedures will result in geological information, I should say rather than maps, many times more complete than has been available without the photographs, particularly with the additional information from magnetometer work. I believe that the careful application of these procedures will lead us to some new mineral deposits more readily than we have been finding them. In regard to discovering mineral deposits, the previous speaker employed a rather difficult method of approach. The way I have suggested is equally difficult and, of course, it will be recognized that this work that I have taken up will be preliminary to such work as he has suggested in geochemistry. A significant factor in the discovery of a Gaspe', Quebec, copper deposit was the easy way that I suggest you all try. One geologist who used his head more than his feet walked in to see my chief at that time, Dr. I. W. Jones of the Quebec Department of Mines. He lust said, "I want a copper deposit, a large deposit of low—grade ore. Where is one?" Dr. Jones turned to him and told him where to go in Gaspe' to look for it, and there it was waiting. For many years Dr. Jones had done much mapping in that region. Most geologists thought that there were no mineral deposits of importance south of the St. Lawrence River in Quebec, and few had looked there; so when the gentleman came along, it gave Dr. Jones an opportunity to tell him where there really was some copper, and this information led to the discovery. I suggest, therefore, that you try that way first, and if it does not work, you will have to resort to photogeological work along with geochemical work. Discussion Dr. H. E. Hawkes, Jr. (Massachusetts Institute of Technology): In what way does photogrammetric work have an advantage over what the geologists have been trying to do otherwise for some time? Dr. Longley: I can give an example applying detailed photogrammetry to the geologic interpretation. Around 1946 I mapped the Bachelor Lake area in the Province of Quebec and showed the prospectors where the ore was. I did a rough contour job using form lines which helped considerably, but I was criticized because, as the detailed work around the mines showed, the elevations did not check with mine, and the engineers said my map was not accurate. It was not intended to be 100 �accurate. Had that same lob been done with a Kelsch Plotter or Multiplex, for example, it would have been a far superior map and would have been of far more help to the mining engineer in his operations and also helped in geological interpretations. Photogrammetry would have yielded a superior map to the one I was able to produce by the routine procedure of photo interpretation. For the geologist making up a map in critical areas, there would be considerable advantage to a detailed map made by the more precise mapping instruments. That was the only place I did run into severe criticism because my map was not good enough. To the people using the maps, the form lines were interpreted as contour lines and they proceeded accordingly. The general situation is that physiography is very important in the interpretation and presentation of geological features, Detailed mapping of surface features, such as can be done with a Kelsch Plotter or Multiplex, provides an excellent physiographic base to aid in the geological interpretation and presentation. 101 �MODERN TECHNIQUES OF PHOTOGEOLOGY AND PHOTOGRAMMETRY IN NATURAL RESOURCE DEVELOPMENT by John C. Bayless Aerial photography has come a long way since the days following World War I when Talbert Abrams helped pioneer aerial surveying and the cameraman hung over the side of the cockpit with a hand—held camera. Today, a military jet can photograph for reconnaissance purposes a 490-mile strip across the United States in less than four hours. But photography and photogrammetry for geologists and engineers are long past the reconnaissance stage and have become precise tools and desirable components of nearly all mapping operations. The aerial camera is the modern surveying instrument in the search for minerals and fuels to support our national economy. The principal value of aerial photographs is that detailed maps can be made from them. The photogrammetry of overlapping pairs of aerial photographs for quantitative data is so perfected that virtually no ground detail is too small to be measured and plotted. Applications in the fields of natural resource development, engineering planning, and area mapping are almost without limit. Photogrammetrically plotted maps are an important supplement to aerial photographs as contact prints because, in plotting, the radial distortion of scale and displacement of images on the photograph due to tilt or relief has been rectified to an orthographic projection. Thus accurate distances and directions can be measured. Topographic contours or control points for structural contours in absolute elevations are often plotted. For field work in densely vegetated areas or in areas with only faint geologic clues, an accurate topographic map has distinct advantages in locating oneself on the photograph and in the field. A geologic map in the full meaning is a geologic contact map with topographic contours. By relating contacts to contours a detailed interpretation is best accomplished. Reconnaissance contact maps are usually prepared by transferring the pattern of formational outcrops from individual photographs onto photographic mosaics. Geologic maps are compiled by photogrammetric plotting using stereoprojection equipment. The production of geologic maps by photogrammetric methods effects savings by reducing the number of supplemental control points which must be obtained by ground survey. In addition, when higher altitude photography is used, the increased area covered by each model, and the fewer models required with less time spent setting up and joining detail between models, result in savings in stereocompilation. From the viewpoint of the photogeologist, stereoprojection instruments partly solve the problems of relating or transferring geology to base maps. These instruments also combine stereoscopy in orthographic projection with the ability to make many measurements more easily than those he now makes on the ground. The trend today is for specialized teams of photogrammetrists to work with teams of photogeo logic 102 �interpreter specialists to produce geologic maps.* Such joint operations bring together the planes, laboratories, photogrammetric instruments, plotting techniques, field operations, reproduction processes and technical and professional staffs to provide an integrated interpretation and mapping program. This seems to be a reasonable approach to applying two specialized techniques to the expanding requirements for geologic mapping and the need for more detailed mapping. Planimetric maps can be constructed by geologists or engineers from aerial photographs using a system of radial—line plotting based on the usual surveying principles of intersection and resection. These methods are not very accurate and most photogrammetrists and engineers, who are concerned with precision mapping, consider them to be of reconnaissance value only. Greater accuracy is obtained by using stereoprojection plotters. The development of new first— order plotting instruments has hastened the adoption of Kelsh and Multiplex photogrammetric instruments by geologists by making available these less elaborate plotters which today generally have a supporting role in mapping for precise engineering projects. A Kelsh stereoscopic projection plott&r is shown in Figure I. Projectors are mounted above a plotting table in such a way that they exactly duplicate, on a reduced scale, the altitude, tilt, and position of the aerial camera at each picture station along the flight line. Working in a dark room the operator sees a three—dimensional image of the topography. By means of a small tracing table which can be moved freely on the plotting table, he traces the ground plan, controlled by known ground stations and corrected for tilt, radial distortion, and scale. Topographic contours can be plotted by using a floating dot in the stereoscopic image of the topography and some known ground elevation control points. The operator can set the dot correctly at elevation control points and, using the contour scale selected, move the dot and tracing table along the given contour, automatically tracing the line on the map. The principles of photogrammetric mapping also apply to structure contouring. If a topographic contour map is not to be prepared, the geologist selects on aerial photographs evenly spaced points along the formation or marker bed boundaries to serve as structure contour control points. He pin— pricks them through the photograph and identifies each on the back. Depending upon the scale, 15 to 30 points per square mile are selected. The photogrammetrist determines the elevations and sometimes the coordinates of these points so that the geologist can then contour the structure on a key bed. Such methods may be three to four times faster and also are more accurate than plane table mapping. In recent years a trend has developed toward the use of special photography flown to suit the needs of given projects. It is often cheaper to fly new photography correctly designed than to attempt to use older photography designed for some other purpose. The best opportunity to save money and time is at this point. For example, when Kelsh plotters are used with a 5X projection enlargement ratio, 1:60,000 photography can be plotted directly to 1:12, 000 map scale. Three to five 1:60,000 photographs cover the area of about thirty 1:20,000 photographs, the usual available scale. The use of this small—scale photography may save one—half to two—thirds the plotting time, some flight costs, and considerable ground control. On the other hand, there is also a demand for new large—scale photography. Stratigraphic and * Abrams Aerial Survey Corporation, Lansing, Michigan is affiliated with Doeringsfeld, Amuedo and Ivey, Denver, Colorado for integrated photogrammetry and photogeologic interpretation. 103 �Fig. I. Kelsh type stereoscopic projection plotter. Spatial model is created by projection of 9" x 9" glass diapositives made from aerial photographic negatives. Tracing of ground plan and measurement of altitude are accomplished by a tracing table which rolls over the manuscript with a pencil lead directly under the illuminated floating dot. geomorphic columnar sections may be better interpreted from stereoscopic study at large scales. Columns showing hard layers and ridge makers are particulary useful to photogeologists. As in the case of precise structure contouring, thicknesses of stratigraphic units are best measured by photo— grammetric techniques. A convenient medium for speeding the work of the interpreter to the user is a reproducible photo— mosaic on the same scale as the contact prints. A recent development is printing the mosaic image on the under surface of reproduction linen. While viewed over a light table, the geology can be transferred to the clear top surface using a stereoscope and the original annotated contact prints. If topographic and structure contour maps are also accomplished on linen at the same scale, these can be fitted and traced directly onto the mosaic. Topographic contours are usually traced on the back side over the mosaic while structure contours are drawn on the top side with other geology. The result is a photograph of the region and superimposed geology with contours which can be viewed separately or together. There is also the advantage of a durable drafting surface on which changes can be made without affecting the photographic image. 104 �The historical principles of interpretatiai of oiogic maps appty to the interpretation of aerial photcphs. In the training of a geologist todoylt is difficult to determine which should be studied fiat because there are Ixisic similarities, diffe-ences, and limits to each. Culture is shown in full detail on aerial photographs while the geologic map depicts only the landmarks considered essential by the mapper. Tie photograph indicates generally what is at the surface and the geologic map usually indicates an interpretation of bedrock beneath the mantle. However, in this latter regard, aerial photographs frequently revl subtle tones, patterns, forms or relief which are keys to the bedrock or structure not evident to a person on the ground. Photographs when viewed as stereo—pairs under a stereoscope revI relative relief while a geologic map compiled photograrnmetrically has topographic contours which indlte actual relief as detailed as required. The fact is. that modern geologic maps are likely to be based on the it-iterpretation of photographs, and have been compiled photogrammetrically. Pitoto—interpretatlon involves more than the identification of features. The interpreter supplements hi direct observation by deduction and by visualizing obscure or hidden features with the guidance of previous experience and reasoning. This is an essential difference between photo—reading and interpretation. The value of the map increases with the degree to which the latter is applied. Both havi a :ommon starting point, the recognition of diagnostic features. Many extellent emples of photogeology are in company files but generally are not available for publication. However, a good list of outstanding photographs has been prepared by the American Geological Institute as Report No. 5 j95J, and isa source of materials for training programs. There are two basic phases of photogeologk 4nterpretaflon. One is the mapping of rock types and formation units and the other is the determinatton of rock 4ructure. Each of these is somewhat specialized in the several fields of economic geology but the objective in any case is the compilation of a geologic map. Consolidated sedimentary rocks are recognized by their stratification which appears on photo-' graphs as banded outcrop patterns, If the beds are horizontal, the contacts will be horizontal and their surface traces will parallel topographic contours. Beds that have been titled and subsequently truncated by erosion crop out as belts. Where streams cross the outcrops a V—shaped pattern develops with the V1s pointing in the direction of dip. Folded beds are often expSssed at the surface by belts which form parallel ridges and valleys, or looped and zigiag ridges wbh canoe—shaped valleys. Antic lines and sync lines are differenttated through analysis of the dip of beds. If the stratigraphic sequence is recognized, anticlinal axes are located along the oldest beds exposed in the center. In a synclin:e the opposite is true. Sedimentary rocks are distinquished on photographs mainly on the basis of stratification, and differentiated by comparative color and resistance to erosion The latter are suggestive only Color depends on the character of the rock and the vegetation at supports Resistance to erosion depends not oniy.on the physical and chemical characteristics of the rock but on the climatic environment as well, Limestone and dolomite, for example, are very susceptible to erosion in humid regions but frequently form ridges in arid regions. Pure limestone and dolomite are characteristically light but impurities produce darker colors. Frequently, distinctive horizon markers rather than formation units are selected to map structure even through the lithology may be unknown. Extrusive igneous rocks are distlnuished mainly by their surface Irregularity, a ground plan �which suggests a mobile form, and association with vents such as cones or fissures. More recent flows are barren and usually dark in color. Geologically ancient lavas may not be recognizable except by a field check of lithology or structure. Massive, intrusive igneous rocks usually appear to cut across stratified rocks with discontinuous contacts. Dikes are recognized on photographs by their linear form, group pattern and by their cross—cutting relations. Petrographic distinctions are rarely possible even though color tone is used to determine form and structure. Joints and fractures are recognized by angular patterns in the drainage or by a grooved or striated appearance of the bedrock. Faults are conspicuous where the outcrop pattern has been offset or interrupted. Fault traces unnoticed on the ground may be prominent on aerial photographs as linear boundaries between areas of contrasting vegetation and soil coloration. An escarpment and color contrast mark the line of a fault in igneous rocks in Figure 2. Fig. 2 . Huronian lavas in upper part of photograph faulted down against intrusive igneous rocks in lower part, Marquette County, Michigan (Photography by Abrams Aerial Survey Corporation). 106 �Iv'Sore widespread ue of color photography is just around the corner for photo—interpretation. Where browns, yellows and greens may be diagnostic, details in rock strata, soils and vegetation may be lost because these colors photograph as,about the same shade of grey on black-and-white photo- grapiy. Another advantage of color photography is that the eye can differentiate about 200 shades of grey in the tone scale between black and white. In contrast, there are about 200,000 different combinations hi the color scale. Reds and whites, gradations in yellows, and even some gradations in whites can be seen on color photographs. Usually one cannot differentiate features depending on these color cfcnges on black—and-white photographs. In this respect, color photography has been particularly useful in outlining areas of leaching around mineralized zones. In the past few years it has been thoroughly demonstrated that bleaching and discoloration by hydrothermal alteration can generally be mapped more rapidly, effectively and accurately using color aerial photography than by ground methods alone.* In some areas blanket alteration up to four miles across has been mapped on color photographs and in others alteration effects limited to the immediate walls of ore bodies can be observed. Alteration mapping on color photographs is being used as a guide to uranium exploration on the Colorado Plateau. Color photographs must be relatively large—scale to register adequate color separation suitable for alteration mapping. Where individual veins are to be delineated, photography should probably be I" — 250' to I" = 500'. Up to I" z 1500' may be used for reconnaissance of mineralized areas. If stratigraphic boundaries, lateral variations, and structure are to be interpreted, scales as small as I" = 2500' may be used. Proper exposure and haze filtration are always critical in color photography. Colored acetate sheets can be used to correct some errors in color reproduction. Filter sheets are also useful In emphasizing certain colors for interpretation purposes. The trend toward wider application of photogeology and photogrammetry in geologic interpretation and mapping is paying off in better maps at lower costs. The details of areas mapped are commercial secrets of the client. However, it is well known that most of the major oil companies and many mining companies are using these exploration techniques at an accelerated rate. As the integration of photogrammetry and photogeology gains momentum, increasing economies can be expected. Many factors have conspred to make this a very brief discussion of the subject. The literature, such as "Photogrammetric Engineering" published by the Society of Photogrammetry, reports many of the newer applications. I will be very glad to correspond at any time on questions concerning the applications of modern photogeologic and photogrammetric techniques. * Abrams Aerial Survey Corporation is affiliated with Colorado Exploration Company, Golden, Colorado for geological and geophysical contracting to the mining industry. The writer is indebted to that company for some data on interpretation of color photographs. 17 �Di Sc U55 iOn Mr. R. A. Spencer (Consolidated Mining & Smelting Company): What are the costs of color photography as compared to black and white? Mr. Bayless: Color aerial photography costs at least twice as much as black-and—white aerial photography. However, what is the cost of aerial photography? It is the sum of the costs of mobilization of a plane and crew, the film, and laboratory processing and is a function of scale, the size of the project, the geographic location and the contractor's estimate of the expected weather conditions. The latter is of particular import in color photography and the requirement for absolutely clear weather usually necessitates much longer stand—by times. Color film costs four times that of black_and_white film but the laboratory costs may be about the same if only color transparencies are delivered. Very small color photographic projects of a few square miles in Michigan may cost about the same as black-and-white photography because of the high unit area mobilization for all small projects. However, black and white photography of medium size projects at 1:6000 scale costs $60 — $100 per square mile and color photography would be more than this. About $20 to $40 per transparency is a representative cost for vertical color photography. This does not appear at first consideration to compare favorably with "government" black-and-white photography which so many of you use. However, the usual government photography is at 1:20,000 scale and is contracted, for large areas, under very competitive conditions for $3 to $6 per square mite. We are faced with similar problems when giving generalizations on costs of photogrammetry and stereo—plotting. Plotting of topographic maps may range from pennies to dollars an acre depending your scale, contour interval, content and relief of the areas. Ground control is hard to estimate until you know the availability and location of existing control and what must be done to bring it to the project area. Control can cost from 50 cents a square mile to 50 cents an acre. Dr. A. W. Jolliffe (Queen's University, Kingston, Canada): It seems to me that these papers have stressed the geologic interpretation of aerial photographs. I think it should be noted that to some extent the photographs themselves are most useful in geologic mapping. I am speaking now from long experience in the northwestern part of the Canadian Shield where we have a lot of barren outcrop and not much overburden as in the area Dr. Longley referred to. Here it is very difficult to make interpretations despite good exposures and the abundance of linear features, and the chief use of the photographs is as an actual base for geologic plotting. One other point in regard to Dr. Longley's procedures: We utilize every available piece of geologic information prior to the interpretation of the photographs and field check afterwards and I suggest that any geologic interpretation is just as accurate as these two necessary procedures. Again, on the basis of my experience, the use of photographs seems to me to be chiefly as bases for plotting. This is heresy to anybody who makes such extensive use of complicated photogrammetric apparatus but my point is this that the geology does not warrant too much in the way of detailed rectification of plotting. The radial—line method is of sufficient accuracy for mast geologic maps. Dr. A. M. Goodwin (Algoma Ore Properties, Limited, Canada): Are there examples in which the difference in cost between color photography and black and white is warranted in the finding of a mineralized area? Mr. Bayless: There are indeed such examples and I am embarassed for not being able to give you 108 �the names of the districts. The work was done by an affiliate of our organization in some of the old Colorado mining districts. Some of the work was done around Aspen. There resulted a number of new discoveries that were identified by colors associated with leaching in areas that had been walkea over for many years by field men who knew the geology. Of course, there are other aerial survey companies besides those represented here tocav. A ne California firm has a large color contract in South America about which you may have reaa National Geogrphic Magazine. They showed recently in Chicago some of the color photog-ap / that was being done in a copper district. I cannot say whether or not they show anything that was not already known but they were or are photographing and presumably interpreting and mapping many square miles. Color photography is one of those things that is looked upon highly by photogrammetrists. I found this when talking to the Atomic Energy Commission people in Grand Junction, Colorado. Photogrammetrists praised the technique though geologists thought black and white was serving their needs about as well on the Plateau. It may be a reluctance to accept something new. There is also the matter of higher costs. We are doing color photography, but I do not want to over sell color. As a matter of a fact it is so touchy" that we are very happy to work in black and white. I should like to make a comment on radial plotting. I do not mean to belittle it. Certainly there is more radial—line plotting than any other type today by individuals and by mining companies with interpretation sections. Many of the things that I have talked about are on the verge of becoming more universally accepted. The use of stereo plotting instruments as a tool for geologists is something that is coming and developing fast. But it is certainly true that there are many projects in which the accuracy of simple radial control is quite satisfactory. There is another trend that has not been mentioned thus far. That is the integrated program of natural resource development in which bed rock geology, soils, and forest and water resources are mapped for engineering planning and design and for exploitation. This program involves the work of many specialists. Projects of this kind are going on abroad, and similar work is being planned in this country too. A question may be raised as to why foreign photogrammetric equipment is being used by many American aerial survey companies. Swiss, German and Italian instruments are all being introduced because they are more efficient and offer control extension capabilities. 109 � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1956 Description An account of the resource Institute on Lake Superior Geology: Geological Exploration. Michigan Institute of Mining and Technology, Houghton, Michigan, May 11-12, 1956. Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Publisher An entity responsible for making the resource available Michigan College of Mining and Technology Date A point or period of time associated with an event in the lifecycle of the resource 1956 Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/405166bf219ff4b76df37c11e3bf0e6f.pdf 21229acc65385c1616b30862a339fe8c PDF Text Text �TABLE OF CONTENTS Page i Program 1 The Petrology of the Beaver Bay Complex ... . .... 2 3 The Critical and Transition Zones of the Eastern Part of the Bushveld Complex . Harry ......... ... Eugene 11. Gehrnan N. Cameron Electrical Methods of Geophysical. Prospecting in the Lake Superior District ......................... C. V. Keller, C. J. Zablocki, F. C. Frischknecht Magnetic Susceptibility and its Correlation with Magnetite Content in Taconite . .. . , i.,.., • ., Charles E. Jahren 5 Geophysical Studies in 7 Geological Implications of Magnetic and Gravity Data of the Lake Superior Basin 8 9 Geology of the Menominee Michigan District, ..... ..... Gordon Northern Minnesota .,.. • S... 12 Iron.-Bearing RichardW. 15 Carl. E. Dutton Problems of the Division of Precambrian Time •.,.,,.............,...,.. Dating of Precambrian Iron Formation The Relation of Shear Joints to a Fault in the Sturgeon Quartzite Problems -- Solved (?) and S. S. Goldich,A. 0. Nier ........ S. S. Goldich, A. 0. Nier, W. Krueger, J. H. Hoffman Tear Unsolved -- In James Trow the Glacial History of Northeastern Minnesota 17' Bayley Stratigraphy of Pre.-Keweenawan Rocks H. 13 Bath George M.. Schwartz in Parts of Northern Michigan U D• H. E. Wright, Jr. A Study of the Iron Silicate Minerals with Special Emphasis on the Iron.Formation in the Cuyuna District, Minnesota ................... Rolland 18 Petrography of the Western Mesabi Range, Minnesota ...... 19 The Mineralogy .of the Metamorphosed Biwabik Iron Formation,Eastern Mesabi Range, Minnesota J. C. L-. Blake A. Beckman Novotny Gundersen �TABLE OF CONTENTS (Continued) Page 20 Alteration Studies at Helen Siderite Mine ,.,.,,.,.,....., A. N, Goodwin 21 The Anim.kie Sea . 2 The Properties of Silica Gel and its Possible Relationship to the Development of Lake SuperiorType Iron Ores .-.......................... 23 2 W. Bartley M. The Role of Interstitial and Combined Waters in the Development of Lake Superior Iron Ores ....... CedrieL. Iversorr G. H. Spencer, Jr. The Mineralogy, Paragenesis, and Origin of the Cuyuria Sulfide Deposits T. M. Han 25 The Genesis of the Lake Superior 26 Peat Research at the University of Minnesota ,........ Moses Passer 27 Recent Spodumene Discoveries in Northwestern 28 Iron Ores of the Pacific Northwest 2 30 Copper Deposits ... Ontario •4 Finds in Northwestern Ontario ... C, Arnstutz G. W. L. C. Greer L. C. Binon Characteristics of Some Iron-Bearing Formations in Northern Wisconsin Recent Iron .. E. .. .. . L. B*ctner ...... .... E • R. Mead �I UNIVERSITY OF MINNESOTA Center for Continuation Study Duluth 12 Institute on Lake Superior April 21-22, 1958 Geology PROGRAM Monday Morning-April 21, 1958 SciencØ Auditorium, University of Minnesota, Duluth 9:00 9:15 General Meeting of the Institute .. GeneraJ. Chairman, Ralph W. Marsden J, M Nolte Welcome ••Øi.$Ia• SESSION I Co-chairmen: 9:30 9:55 H, M. Gehman: E.. N. Cameron: 10:20 (3. V. Keller*, 1O:45 C. E. Jabren: Henry Lepp, Thomas E. Stephenson PETROLOGY OF THE BEAVER BAY DIABASE THE CRITICAL AND TRANSITION ZONES OF THE EASTERN PART OF THE BUSHVELD COMPLEX C. J. Zablocki & F. C. Frischknecht: ELECTRICAL METHODS OF GEOPHYSICAL PROSPECTING IN THE LAKE SUPERIOR DISTRICT MAGNETIC SUSCEPTIBILITY AND ITS CORRELATION WITH MAGNETITE CONTENT IN TACONITE 11:10 11:35 (3. 12:00 LUNCH GEOPHYSICAL STUDIES IN NORTHERN MINNESOTA GEOLOGICAL IMPLICATIONS OF MAGNETIC AND GRAVITY DATA OF THE LAKE SUPERIOR REGION MAIN BALLROOM, KIRBY STUDENT CENTER 3, D, Bath: M. Schwartz: Co-chairmen: 2:00 R. W. Bayley: 2:25 C. E. Dutton: SESSION II John W. Gruner, Ralph W. Marsden GEOLOGY OF TH MENOMINEE IRON-BEARING DISTRICT, MICHIGAN STRATIGRAPHY OF PRE-KEENAWAN ROCKS IN PARTS OF NORTHERN MICHIGAN S. Goldich*, A. 0. Nier: PROBLEMS OF ThE DIVISION OF PRECAMBRIAN 2:50 S, 3:15 S. S. Goldich, A. 0, TIME Nier, H. N. Krueger*, H OF PRECAMBRIAN IRON FORMATIONS J. Hoffman: DATING COFFEE BREAK LI: : 10 James Thow: 35 IL 7:00 RELATION OF SHEAR JOINTS TO A TEAR FAULT IN THE STURGEON QUARTZITE SOLVED AND UNSOLVED PROBLEMS EN THE GLACIAL HISTORY OF NORTHEASTERN MINNESOTA MAIN BALLROOM, KIRBY STUDENT CENTER -- E. Wright, Jr.: DINNER Speaker: Howel Williams Topic: "VULCANISM AND GLOWING AVALANCHES" Tuesday Morning, April 22, 1958 SESSION 9:00 III Co-chairmen: Jack V. Everett, Josiah Royce R. L. Blake: A STUDY OF THE IRON SILICATE MINERALS EMPHASIS ON WITH SPECIAL THE IRON FORMATION IN THE CUYUNA DISTRICT, MINNESOTA �ii Lake Superior Geology 9:20 9:40 C. A. Beckman: J. N. 10:00 10:25 A. M. 10: C. L. L15 M. W. 11:05 G. H. 11:25 T. M. 12:00 LUNCH PETROGRAPHY OF ThE WESTERN MESABI RANGE, MINNESOTA Gundersen: THE MINERALOGY OF THE METAMORPHOSE]) BIWABIK IRON FORMATION, EASTERN MESABI RANGE, MINNESOTA ALTERATION STUDIES AT HELEN SIDERITE MINE Goodwin: Bartley: ANIMIKIE SEA Iverson: THE PROPERTIES OF SILICA GEL AND ITS POSSIBLE RELATIONSHIP TO THE DEVELOPMENTOF LAKE SUPERIOR TYPE IRON ORES Spencer, THE ROLE OF INTERSTITIAL AND COMBINED WATERS IN THE DEVELOPMENT OF LAKE SUPERIOR IRON ORES Han: THE MINERALOGY, PARAGEMESIS, AN]) ORIGIN OF THE CUYUNA SULFIDE DEPOSITS - MAIN BALLROOM, KIRBY STUDENT CENTER Jr.: SESSION IV Robert L. Heller,. Fred 1 Jensen Co-chairmen: 1:30 1:50 2:10 2:30 2:50 . C. Arnstutz: 3:10 E. R. Mead: * Passer: W. L, C. Greer: Moses L.. C. Binon: E. L. Buetner: Indicates THE GENESIS OF LAKE SUPERIOR COPPER DEPOSITS PEAT RESEARCH AT THE UNIVERSITY OF MINNESOTA RECENT SPODUMENE DISCOVERIES IN NORTHWESTERN ONTARIO IRON ORES OF THE PACIFIC NORTHWEST CHARACTERISTICS OF SOME IRON-BEARING FORMATIONS IN NORTHERN WISCONSIN RECENT IRON FINDS IN NORTHWESTERN ONTARIO speaker FACULTY C1 AMSTUTZ •.. M. ,. .. .•..,.. Department of Geology, Missouri School of Mines, Rolla, Missouri , Bartley, Creer g W. BARTLEY Associates, Port Arthur, Ontario, Canada G. D. BATH U. S. Geological Survey, Menlo Park, California R. W. BAYLEY U. S. Geological Survey, Mineral Deposits Branch, Menlo Park, California C • A. BECKMAN ., FRED Z. BERGER , . •,. . ..... Mines ... ,,, . , .. L. C. BINON E • L. of Minnesota Director, Center for Continuation Study, University of Minnesota Northern Pacific Railway Company, St. Paul BUETNER ... . ... . ROLLAND BLAKE Experiment Station, University .. .. . . Jones g Laughlin Steel Corporation, Pittsburgh, Pennsylvania ...... Graduate Student, Department of Geology, University of Minnesota E. M. CAMERON ,..,,.,.,.. Professor of Head, Department of Geology, University Wisconsin, Madison, Wisconsin �ila. Superior .Lake Geology MERRILL K. CRAGUN . ., .. Course Coordinator, Center for Continuation Study, University of Minnesota C E. Regional Geologist, U. S. Geological Survey, University of Wisconsin, Madison, Wisconsin JACK V. EVERETT Geologist, W. S. Moore Company, Duluth H • M. GEMMAN . . , . 0.• • • • . S. S GOLDICII Jersey Production Research Company, Tulsa, Oklahoma Professor of ceology, University of Minnesota A • N. GOODWIN ,... .... .-. Ge'blogist, Algoma Ore Properties, Ltd., Jamestown, Ontario, Canada W. L. C. GREER .. . JOHN W, GRUNER J• Bartley, Greer & Associates, Port Arthur,. Ontario Canada Professor of Geology, University of Minnesota 4. GUNDERSEN Graduate Student, Department cf Geology, University cf Minnesota T., H, HAN Cleveland-Cliffs Iron Company, Ishpeming, Michigai ROBERT L. HELLER Associate Professor F Head, Department of Geology, Duluth Branch of the University of Minnesota C. L. IVERSON Oliver Iron Mining Division, U, S. Steel Corporation, Duluth C. E. JEHREN Assistant Professor of Science, Junior College and U. S. Geological Survey, Austin FRED 'F JENSEN .,........, Snyder Mining Company, Chisholin, Minn. G• V • KELLER H• W • . . . . . . . .. . . KRUEGER HENRY LEPP ... U. S. Geological Survey, Geophysics Branch, Denver, Colorado of . .. . • • . • . . . Department .. .. • .. ... Associate Professor of Geology, of the University of Minnesota Geology, University of Minnesota Duluth Branch RALPH W. MARS DEN Geological ManageD of Investigations, Oliver Iron Mining Division, U. S. Steel Corporation, Duluth E. R. MEAD Bartley, Greer & Associates, Port Arthur, Ontario, Canada J. M. NOLTE ........•.,.... Dean, General Extension Division, University of Minnesota �iv Superior Geology ES PASSER Department of Chemistry, Duluth Branch of the University of Minnesota LREMINGTON .......•.,. Resident Manager, General Extension Division, University of Minnesota, Duluth Branch SIAH ROYCE . ., .. . . , , , , . Geologist, Pickands, Mather Company, Duluth N. SCHWARTZ ............. Professor, Director, Minnesota Geological Survey University of Minnesota H • SPENCER, Jr. . LIIOMAS E. STEPHENSON JAMES TROW ti Xis .. rn Li rmrrtirr flI\.L.3UL, UL\ y' Geologist, Oliver Iron Mining Division, U. S. St'eel Corporation, Duluth Resident Geologist, Jones •g Laughlin Steel Corporation, Virginia Geology Department, Michigan State University,, East Lansing, Michigan Associate Professor of Geology, University of Minnesota �1 THE PETROLOGY OF THE BEAVER BAY COMPLEX Harry N Gehman Three gabbroic intrusions, with minor associated rock types form the Beaver Bay complex in southeastern Lake County, Minnesota. The gabbros intrude the Middle Keweenawan North Shore volcanic group. The oldest intrusion, the Beaver River gabbro, contains calcic plagioclase (An65), medium olivirie Xenoliths of (Fa40-.55), titanaugite (Ca4Mg38Fe22), and accessory mInerals. anorthosite are abundant locally in this unit, together with a few xenoliths of leucocratic granite, The second intrusion, the Beaver Bay ferrogabbro, shows marked composiDifferentiation tional variation from the lowest to the highest exposures. through crystal settling has produced a progressive change in the composition o].ivine, clinopyroxene, and plagioclase. of the primary precipitate minerals: The progressive change in olivine composition from Fa66 to Fagg allows subdivision of this unit into hortoriolite-, ferrohortonolite- and fayalite-ferrogabbro. High-calcium clinopyroxene likewise shows a progressive change in iron and magnesium content from augite (Ca3gMg33Fe28) to ferrohedenbergite Pigeonite, inverted pigeonite, and primary hypersthene are (Cai13t4g02Fe55). present as interprecipitate phases in the lower part of the intrusion; however, rocks with olivine more iron-rich than Fa82, ferroaugite is the only pyroxene present. Absolute iron-enrichment of the rocks is indicated by chemical analyses of samples from varying heights in the intrusion.. Silica— and alkali enrichment become apparent only in the upper fayalite-ferrogabbro where large in amounts of micropegmatite and thick sodic plagioclase rims are present. The Black Bay gabbro forms dikes and small sills surrounding and intruding the ferrogabbro. It is generally coarse-grained with numerous coarser pegIts chemical and mineralogical composition is very similar to matitic zones. that of the numerous pegma-titic veins and schlieren common to fine-grained gab— broic sheets throughout the world. �2 THE CRITICAL AND TRANSITION ZONES OF THE EASTERN PART OF THE BUSHVELD COMPLEX Eugene N. Cameron Structural and petrologic features of the Critical and Transition zones of the eastern part of the Bushveld Complex, disclosed by detailed mapping and study of selected areas, throw further light on the evolution of the complex and suggest additional investigations that may be fruitful. Both Critical and Transition zones vary in composition and sequence of rock units. The Critical Zone, the more intensively studied of the two, is divisible along strike into at least three sectors, differing in sequence of maIn the southern and central jor units. The northern sector is poorly exposed. sectors, the Critical zone consists of a lower pyroxenite series and an upper anorthosite series, but the sequences of units in these series are not the same in the two sectors. Relations between sectors are obscured by faulting and folding along the line of the Steelpoort VaJ.ley. Cognate enoliths, discontinuities, and. irregularities in the layered structure of the Critical tone, together with tepetitions of rock types, indicate formation from a moving rather than a static magma. Penecontemporaneous folding and fracturing indicate local disturbances during consolidation, but clear evidence of major disturbances is not at hand. The occurrence of blocks of metamorphosed sediments at points well above the floor of the complex is a feature deserving further study. The xenoliths may be a part of the more general problem of adjustments of the floor and roof of the complex during differentiation and consolidation. At present, such movements cannot be fully distinguished from movements that took place after consol. idation. Many of the rock types of the Critical zone are satisfactorily explained by a combination of fractional crystallization, gravitative settling, and mechanical sorting of crystals due to variations in velocity of magmatic curThe more extreme types of anorthosites, pyroxenites, and chromitites rents. Possible eactions during and afappear to require supplementary processes. ter burial of settled crystals, and the influence of thermal gradients between the magma-accumulate interface and the roof and floor of the complex appear to deserve further study. �3 ELECTRICAL NETHODS OF GEOPHYSICAL PRCSPECTING IN THE LAKE SUPERIOR DISTRICT G. V. Keller, C. J. Zablocki and F. C. Frischknecht The electrical propertie of ores -and host rocks and Ithe uses of electromagnetic methods of prospecting have been studied in the Lake Superior iron and copper districts, Both borehole and laboratory measurements of electrical properties were made. The investigations suggest that electrical surveys may be a useful sup. plement to magnetic surveys. In many cases, for example, iron ores could be distinguished from the adjacent rocks because of their higher conductivities. Similarly, in the native copper ores from the southern shores of Lake Superior, polarization was found to correlate with the amount of copper. electrical Experimental electromagnetic surveys were made in three areae where the A conductive zone in iron-formation is covered by 100 feet of glacial till. the hanging wall could be traced in these areas, but the effect of the ironThe possibility of distinguishing beformation itself could not be detected. tween the effects of induced and remanent magnetization was also indicated by the electromagnetic measurements. �4 MAGNETIC SUSCEPTIBILITY AND ITS CORRELATION WITH MAGNETITE CONTENT IN TACONITE Charles E., Jabren Magnetic susceptibility measurements have been made on samples of drill. core from iron-formations and'other magnetic rocks in northeastern Minnesota. The relation k = 0.001157 V1.39' where k is the susceptibility and V is the volume percent rnagnetite between the limits 10 and 1i0 percent was found to hold for taconite in the eastern end of the Mesabi range. Susceptibility was measured by inserting each specimen change tite in self-inductance o the into a HelmhQltz coil and recording the coil as indicated by an ac greatly. were Magne- content for each depth interval was determined by magnetic separation. The susceptibility of individual samples from the same rock ed bridge. formation differ- In an effort t get reliable averages, as many as 250 samples measured from some holes, �5 GEOPHYSICAL STUDIES IN NORTHERN MINNESOTA Gordon D Bath The physical properties of rocks in northern 'Minnesota are being studied to obtain a better understançling of the regional geology. A major part of the investigation consists of studying the magnetic properties of large rock units to determine their effects on the earth's magnetic field. Other phases of the work include regional gravity measurements in the Cuyuna district, varius types of electric logging in drill holes, and eJ.ectromagnetie surveys to trace the iron-formation beneath glacial drift. Many of the aerornagnetic anomalies over iron-formations in areas cf moderate to intense metamorphism are attributed to the effects of regional remanent magnetization alone. Such anomalies occur over iron-formations of the East Mesabi, Gunflint, Vermilion and South Cuyuna districts, and in th ironformations of the Cogebic district near Mellen, Wisconsin. In the Duluth area, magnetic lows caused by remanent magnetization are found over thick sequences of gabbro and extrusive rocks near the base of the Duluth gabbro. During tjie past years traverses were run along roads using a totalfield magnetometer. These measurements siow there is remanent magnetization in the lower cherty member of the Biwabik iron—formation in the Main Mesabi. district, and locally in the iron-formations of the North Cuyuna district. �6 GEOLOGICAL rMPLICATIONS OF MAGNETIC AND GRAVITY DATA OF THE LAKE SUPERIOR BASIN George M. Schwartz The great syncline which is partly occupied by Lake Superior presents many problems which have been only partly solved. Geophysical data accumulated In recent years from many sources furnishes evidence regarding some of the problems. There has long been a suggestion responfault the straight shore-line and deep water offshore along the Minnesota coast. Flights with the airborne magnetometer across the syncline including as well as gravity and geological data, fail to confirm the exist- structural sible for the lake, that a is ence of th fault and it is of reasonable certainty that such a fault does not exist. The Douglas fault, which is well defined on geological evidence,, is characterized by a very large negative magnetic anomaly. Another problem has been the possibility of an extension of the Duluth Gabbro beyond the abrupt ending of outcrops to the north of the St. Louis River at West Duluth. Aeromagnetic profiles fail to indicate any large, near surface mass of gabbro south of Duluth. If the gabbro at Duluth were continuous with gabbro on the south limb in Wisconsin, it would be expected that it would also outcrop around the southwest end of the syncline. Such does not seem to be the case. Local details of the aeroinagnetics furnish important data on the geology where the rocks are buried beneath a heavy cover of glacial drift. A local magnetic low occurs along the west contact of the gabbro as was shown by ground work in l9L2 and confirmed by aeromagnetic data. The lower part of the gabbro (layered series) and the flows beneath the gabbro surprisingly are characterized by a regional magnetic low, but the flows above the gabbro and associated diabases generally produce a magnetic high, as expected. .A large, broad magnetic high in the vicinity of Culver, between Cloquet and the Mesabl, may result from a deeply buried iron formation. Work is being continued on these anomalies by the United States Geological Survey. �7 GEOLOGY OF THE MENOMINEE IRON-BEARING DISTRICT, MICHIGAN Richard W. Bayley The Menominee iron-bearing district includes 150 square miles in southern Dickinson County, Michigan. In the period 1877 to 1936, 85 million tons of iron ore were extracted from its mines, most of it of Bessemer grade, but the district is now virtually inactive, The district has been recently studied by geologists of the U. S. Geological Survey and the Geological Survey Division, Michigan Department of Conservation, as a part of a continuing project to re evaluate the Precambrian iron ranges of Michigan. The r'ocks are mostly of Precambrian age, capped here and there by Cainbrian sandstone, and extensively covered by Pleistocene glacial deposits. Two main divisions are recognized, lower Precambrian rocks (Archean of older reports), and middle Precambrian rocks, the Animikie series (Huronian series of The rocks of the two major divisions are separated by a proolder reports). found unconformity. The Animikie series, which corresponds in the middle and upper parts to the Animikie group of Minnesota, is composed of three groups of From oldest to youngest, rocks separated from one another by unconformities. The these are the Chocolay group, the Menominee group, and the Baraga group. Mafic dikes and sills of AnMenominee group contains the major Iron-formation. imikie age cut every formation. The gross structure of the district is a northwest—striking trough. The trough is underlain by steeply folded Animikie rocks, which are flanked by domal areas of lower Precambrian (pre-Aniinikie) gneiss, granite and greenschist. The older rocks north of the trough are chiefly gneiss, overlain unconformably by Animikie strata. The older rocks south of the trough are altered volcanic rocks which are cut, in turn, by quartz diorite, and granite, both large scale in.trusives. The internal structure of the trough is dominated by three major strike faults which separate the Animikie rocks into monoclinal blocks, and separate the Anirnikie rocks from the pre-Aniniikie rocks along the south flank of the trough. The two central fault blocks form northwest-striking ridges, The formations of the ranges referred to as the north and south iron ranges. dip steeply south or are overturned and dip north. Both ranges show second order folds, most of them west-pitching right-lateral folds, some overturned, some faulted along over-extended south limbs. Most of the high grade iron ore bodies mined in the district were related to such structures, particularly to pitching synclines. The iron-formation of the Menominee group is composed chiefly of quartz and iron oxide minerals, and averages approximately 32 percent iron. The prospect for finding new high grade ore bodies is not encouraging, but some favorable areas have not been explored. The economic utilization of the iron-formation entails problems of beneficiation similar to those encountered with Mesabi �e taconjtes. The area of iron-formation close to the surface in the district is roughly 14,000,000 square feet, which equals about 140,000,000 tons of ironformation, or about 70,000,000 tons of concentrate, for a depth of 100 feet. the Brier slate member, which lies between the two iron-bearing members of the Vulcan formation, and which contains an average of 18 percent iron, could also be beneficiated, mining would be simplified and the quantity of oricentrate from a given property would be increased by 30 percent. If �9 STRATIGRAPFIY OF PRE-KEWEENAWAN ROCKS IN PARTS OF NORTHERN MICHIGAN Carl E. Dutton U. S. Geological Survey Professional Paper 3]MC cf the ahove title, pre- pared by H. L. James, summarizes the results of 15 years of cooperative investigation with the Michigan Geological Survey in the study of Eron and Dickinson counties.. The areal and structural basis of the principal nomenclature, as shown in the following table modified from the report, will be discussed. �_____________ _______ ____________ _____________ ___________ 10 LITHOLOGIC SEQUENCE OF PRECAMBRIAN ROCKS IN IRON AND DICKINSON COUNTIES, MICHIGAN Upper LecamL7rlan Dabase dikes and 1 Keweenawan i V sills (probable age about 1100 million years) Intrusive contact V 3rani intrusive, rocks (probable age 1LOO million years) intrusive contact - Metadiabase and V V metagabbro Intrusivecontact— Fortune Lakes slate Stambaujh formation Hiawatha graywacke Paint River V - Middle V V - V Michigamme slate Baraga Animikie series V Wauseca pyritic member Badwater greenstone Precambrian V Rivertoñ iron-forrriation Dunn Creelc slate with Group OUP Amasa formation Fence River formation Hemlock greenstone with Mansfield and Bird iron-bearing slate members I V V Goodrich quartzite V Unconformity Loretto - slate member Curryiron-bearing member Brier slate member formation Traders iron-bearing member Feich formation Vulcan iron- Menominee gr P - - V —----unconformity Randville Chocolay group dolomite Saunders formation Sturgeon uartzite - Fern Creek formation Unconformity — V V Gneissic granite and other crystalline rock Intrusive or replacement contact ? _? Six-Mile Dickinson Lower Precambrian - Skunk Creek member East V V V V -- Lake amphibolite So].berg schist, with V Branch arkose Unconformity Granite V V OrlQ) - gneiss V V Quartzite and schist (small bodies included in granite gneiss) j 0' �11 PROBLEMS OF THE DIVISION OF PRECAMBRIAN TIME S. S. Goldich and A 0. Nier Division of the Precambrian based on rock types or degree of metamorphism is unsatisfactory. A0/K10 dating now in progress supports .a three-fold division of the Precambrian in the Lake Superior region. Although many problems remain to be solved, tentative dates for the three divisions are. as follows: Late Precambrian Middle Precambrian Early Precambrian 1.6 2.5 0.5 b y - 16 b y older than 2,5 b y The oldest A0/K0 date obtained f or rocks in the Lake Superior region It appears likely that present day radioactive dating methis about 2.7 b y. ods may prove inadequate to resolve time beyond 2.7 b y, although geologic evidence clearly indicates that sedimentary processes were activa before this date. The end of Middle Precambrian time is marked by folding and metamorphism of Animikian and equivalent sediments in an east-west belt extending from Minnesota to Michigan. Deep-seated metamorphism was accompanied by intrusion of granitic magma. The Keweenawan North Shore volcanic group and the Duluth gabbro complex are assigned to middle Late Precambrian. The main gabbro intrusion is dated at 1.1 b y, but folding and metamorphism of the extent developed at this time in the Grenville Province remains to be recognized in the Lake Superior region. �12 DATING OF PRECAMBRIAN IRON FORMATIONS S. S. Goldich, A. 0. Nier, H. W. Krueger, J. H, Hoffman Precambrian iron formations have been studied intensively by geologists and problems of origin and correlation have ranked high in these investigations. Progress of an investigation to date the iron formations of the Precambrian of North America is reported. A0/K10 dating indicates that iron formations were involved in each of the major orogenies of the Precambrian of the Canadian Shield. Soudan-type of iron formations in Minnesota and Ontario were folded in an orogeny dated at 27 b y. Mesabi-type of iron formations in Minnesota, Wisconsin and Michigan Iron formations in Quebec (Ungava— were involved in folding at about 1.7 b y. type) were folded in Geologic the 1.1 b y Grenville orogeny. data suggest that iron formations were deposited during each of three major divisions of the Precambrian, as well as at different times within the divisions. Further geologic studies are needed. the Two periods of mineralization are inferred for the Soudan Mine in Minnedates on samples related to mineralization following folding in Early Precambrian times A younger sericite (1.7 b y) indicates that the deposit was reopened at the time of the Middle Precambrian (post-Animikian) orogeny sota by A'40/K40 of sericite. The older sericite (2.5 b y) is �13 THE RELATION OF SHEAR JOINTS TO A TEAR FAULT IN THE STURGEON QUARTZITE James Trow Six miles east of Norway, Michigan, adjacent to a dam across the Sturgeon River, slates and conglomerates of the Fern Creek formation and the Sturgeon quartzite are overturned and dip steeply northeastward. These strata are cut by northeast-trending tear fau1ts that dip steeply southeastward. In the slates, east—striking slaty cleavage anomalously dips vertically and not at a mc'e gentle angle than the overturned beds. In the quartzites, conjugate shear joints strike essentially east; one set dips gently north, the other gently south. A third set of joints is parallel to the faults. This discussion concerns the relation of the conjugate shear joints to one of the faults. A simplified solution for A, B and C tectonic axes in brittle (competent) rocks is here presented: Instead of bisecting the actual acute angle between conjugate shear joints as plotted on a stereogram to find the direction (C) of maximum shortening of the rock, as proposed by Bucher (1920, Jour. Geology, pp. 716-717), here the obtuse angle between the face poles lie on the ACplane; the contemporary B.. fold, axis is perpendicular to this plane. this area, the slaty cleavage (AB—plane) in the Fern Creek formation axis as determined by bisecting the angle between shear joints of the quartzite. Both structures, therefore, are presumed to be contemporaneous; both are presumed to be younger than the overturning of the strata. The angle between shear joints increases from 414 away from the fault In is perpendicular to the C to a maximum of 92° adjacent to the fault. parallel to the fault. Contours of these values trend Two promising hypotheses are examined to explain the geographic relation between conjugate joints and the fault: (1) The more traditional explanation involves uniform stress anisotropism imposed upon a rock unit of geographically varying internal properties; i • e,, the quartz ite near the fault was, more ductile (less competent) than elsewhere during jointing because of aqueous solutions and high temperatures of hydrothermal origin. This hypothesis is rejected because the timing required by the hypothesis does not correspond to the paragenesis of structural events as inferred from field and thin section evidence. (2) A less conventional explanation involves geographica1ly non-uniform stress anisotropism imposed upon a rock unit of geographically uniform properties so that in the vicinity of the pre-existirig fault, rejuvenated fault movement acted as a safety valve to relieve local stress on the rock. Trigonometric stress analysis based on Coulomb's equation for friction suggests that for angles between joints here observed, local diastrophic force farthest from the fault was 2.' times as much as local stress on the rock adjacent to the fault, all other things being equal. The latter hypothesis, reached through inductive reasoning from field data, is further corrobo- �IL& rated by Seigel (1950, Trans. Am. Geophys. Union4 pp 611-619) who reached the same conclusion on theoretical grounds alone4 through deductive mathematical logic. A U-stage petrofabric study of the quartzite and a model experiment are planned for further investigation of these phenomena. The economic applicatioi of this principle lies in the marked savings that should result from such a study of joints in planning an exploratory drilling program for direct shipping iron ore at. the intersection of an iron formation an iron formation should indicate (1) the the most steeply dipping of the conjugate (gently dipping — not parallel to the fault) shear joints, (2) the strike and dip of the tear fault through the quartzite from a statistical analysis of the steeply dipping joints (parallel to the fault), and (3) the expected direction of refraction (if any) of the fault as it passes from the quartzite into more ductile (less competent) beds, and a tear fault. Jointed quartzites, or other brittle roøk, near location of a tear fault nearest to �15 PROBLEMS - SOLVED (?) AND UNSOLVED IN THE GLACIAL HISTORY OF NORTHEASTERN MINNESOTA H. E. Wright, Jr4 Recent field studies of glacial deposits in northeastern Minnesota, pursued with the support of the Minnesota Geological Survey, have revealed the record of fluctuations of three late Pleistocene ice lcbes: (1) The Superior lobe of red' drift, perior basin,. whose source was the Lake Su- (2) The Rainy lobe of dark gray to bro'p. drift, brought by ice from the northeast. (3) The St. Louis sublobe of the Des Moines lobe, composed of yellowish—brown drift of northwestern source. Earlier Pleistocene drifts are exposed in the iron mines but their relations are obscure. As currently interpreted, the sequence of glaciation in the late Pleistocene is as follows: (1) Cary subage of Wisconsin glacial age. Rainy and covered entire northeastern quarter of State.. (2) Cary-Mankato intervaL. Superior lobes Ice retreated into Lake Superior basin. Superior lobe readvanced to Lake Mile Lacs. Rainiiobe may have stood at Vermilion moraine. (3) Mankato subage.. (4) Mankato-Valders interval (Two Creeks interstadial). treated into Canada. Large lake in Superior basin. (5) Ice re- Valders subage. Superior lobe readvanced out of west end of basin, extending west to Lake Mille Lacs and north to Mesabi Range, bringing red clayey till and reworked lake clays. Contemporaneous advance of St. Louis sublobe from west to a broad zone of junction with the Superior lobe extending from Aitkin (Aitkin County) to Aurora (St. Louis County). (6) Late Valders. Retreat of ice, with formation of glacial lakes Aitkin, St. Louis and Duluth. The above sequence is based on stratigraphic and geomorphic relations and is supported by radiocarbon dates from adjacent regions. These dates place the Cary. subage about 13 ,000 years ago for this area, the Mankato about 12,000 and the Valders about 10,500 years. �16 em Some of the major unsolved problems in the glacial history of northeast Minnesota include the following: (1) Relationship between the Rainy and Superior lobes during the Cary. (2) The extent of deglaciation during the interstadial intervals, (3) The source of carbonate in the red Valders drift of the Superior lobe. (4) The relation of the Valders advance to the development of Lake Agassiz in northwestern Minnesota. (ilacial (5) The nature of the junction of Superior and St. Louis sublobes dur— ing the Va].ders, and the associated drainage relations. Discovery of buried soils, bones, peat and wood, in any of these younger glacial deposits will aid in solving some of these problems through their conThe basic task, tribution to climatic reconstruction and radiocarbon dating. however, is field study of stratigraphic and geomorphic relations, accompanied by appropriate laboratory work. �17 A STUDY OF THE IRON SILICATE MINERALS WITH SPECIAL EMPHASIS ON THE IRON-FORMATION IN THE CUYUNA DISTRICT, MINNESOTA Roiland L. Blake Petrographic and mineralogical studies were made on samples of relatively unoxidized, silicate-rich iron-formation from the central part of the Cuyuna District and from the Troy pit, near Eveleth, in the Mesabi District. Most f the open pit and drill core samples from. the Cuyuna District re-a present the thin-bedded facies described by Schmidt of the U. S. Geological Survey. The open pit samples are from the maL' iron-formation and some drill Textures and structures of core samples are from the upper iron-formation. Minerals identified were carbonate, sti]-pnomelane, these rocks are described. minnesotaite, chlorite, a kaolinite-type mineral that is not greonalite, non—. tronite, amphibole, quart, magnetite., hematite and goethite. Evidence will be presented to show that the iron carbonate is usually rich in manganese; this carbonate appears to be the primary sourceof manganese found in the manganifMineral associations as related to metamorerous iron. ores of the district. phism are discussed. Samples of silicate-rich rock from the upper cherty member of the Biwabik iron-formation at the Troy Pit are described. The rock contains a green silicate with a kaolinite-type structure and varying amounts of either fine hematite or of coarse magnetite and martite. Three samples of stilpnomelane and one of minnesotaite were purified from fissure-fillings in the main iron-formation of the Cuyuna District. Their chemical analyses, optical properties, DTA curves, and X-ray diffractometeD powder patterns are. presented and results of several other tests are discussed. �18. PETROGRAPHY OF THE WESTERN MESABI RANGE, MINNESOTA C. A. Beckman About 200 samples from the Western Mesabi (Hibbing to the West Itasca County line) have been studied. Most of the samples are from unoxidized Biwabik formation, with a few samples from the Virginia and Pokegama formations, and with very few samples in or near any known ore bodies. The Virginia formation occasionally shows development of lineation as a result of the recrystallization of clay minerals, and other minerals include quartz, siderite, chlorite, graphite and pyrite. Most of the samples of the Virginia are fresh and show only slight decomposition for a few feet at the very top. Minerals in the Upper Slaty member are mainly quartz, siderite and stilpnomelane, with minor magnetite and chlorite. Quartz, siderite and stilpnomelane are quite often intimately intergrown, with quartz and siderite occasionally present as microspherulites. Granules are rare in the Upper Slaty. Fresh material from the tipper Cherty member is found east of Keewatin, with. very little, if any, fresh material west of Keewatin. The chert granules almost always show some recrystallization. The Lower Slaty member is thin In the West Mesabi, usually about 15 feet thick, locally up to kO feet thick, and pinches out west of Coleraine. The only fresh material was found east of Keewatin. Fresh material from the Lower Cherty member west of Nashwauk is usually found only in drill holes close to the southern boundary of the Biwabik formation outcrop. There appears to be a persistent zone of oxidation west of Nashwauk, which includes the Upper Cherty, Lower Slaty and about the top one hundred feet of the Lower Cherty.. Minerals in the Lower Cherty are chert, minnesotaite magnetite, greenalite, stilpnomelane, siderite, calcite and chlorite. Minnesotaite and greenalite are often intimately associated; carbonate has often replaced the silicates and chert granules; and the chert granules often show syneresis cracks and occasionally appear broken. Thin magnetite bands of tn show minor shearing and brecciation. The amount of carbonates and sillcatés appears to increase toward the bottom of the Lower Cherty.. The "red basal taconite" was found in every hole which cut the Pokegama formation. This was the only unit in which oolites were found. Hematite is very fine-grained, with much of it being less than .005 mm. in diameter. Other minerals are quartz, carbonate and chlorite. The Pokegama formation contains quartz csf igneous, metamorphic and sedimentary origin, usually with some feldspar and, occasionally, a chlorite cement. �19 THE MINERALQ\GY OF THE METAMORPHOSED BIWABIK IRON FORMATION \EASTERN MESABI RANGE, MINNESOTA J. Novotny Gundersen For subdivided cores from ination of the purposes of this investigation, the Biwabik iron formation was into 2L jneinbers that can be identified in. almost all diamond drill the Eastern Mesabi Ranges, In summarizing the mineralogical inforthis brief report, the less appropriate but more common terms, cherty and slaty, will be used Stratigraphic control, presumably by reason of initial composition, is most apparent from the almost ubiquitous occurrence of olivine near the bottom of the Upper Cherty and throughout the Lower Slaty and from the relative scarcity of olivine elsewhere in the strata. Some hypersthene and minor amounts of grurierite may have originated during the formation of these magnetite-quartz-olivine hornfelses. Minor amounts of idocrase, wollastonite and andradite also reflect the initial composition of the carbonate horizons above the Upper Slaty. Metasomatic mineral assemblages occur in all taconite horizons intruded Within the intruded taconite horizons, hedenbergite, CaFe rich carbonate, ferrotremolite, potash and plagioclase feldspar, chalcopyrite and pyrrhotite are the most obvious metasomatic additions. Hypersthene, alinandite and epidote occur only locally adjacent to the pegmatites and are probably controlled by the initial composition of the taconite horizons in The peginatitic veins consist of varying amount of quartz, which they occur. potash feldspar and ferrotremolite with subordinate amounts of biotite (now mainly chlorite), pyrite, chalcopyrite, Ca-Fe rich carbonate, hypersthene and plagioclase and minute amounts of muscovite and molybdenite. by pegrnatitic veins. Olivine-bearing hornfelse, as well as taôonite containing metasomatic mineral assemblages, are of varying grain size, depending upon their proxim.The coarse-grained, ity to the gabbro or pegmatite contacts, respectively. recrystallized or reconstituted rocks are only slightly replaced by grunerite but most of the material bedded between magnetite layers or lame llae of the prevailing less coarse-grained taconite more distant from these contacts now consists mostly of grunerite. Within the transitional rock types between these two extremes, the late replacement or reconstitution nature of grunerite is clearly distinguished from the earlier olivine, hypersthene, hedenbergite and chert-magnetite assemblages that are replaced by grunerite. The chert—magnetite assemblages are commonly present as relics preserving granules and other primary sedimentary structures. �20 ALTERATION STUDIES AT HELEN SIDERITE MINE A• M Goodwin The Helen iron. formation and associated siderite ore bodies is contained in an assemblage of Precambrian volcanic flows and pyroclastics. The asseinblage has been tilted nearly vertical; the erosion surface thus presents stratigraphic cross-section. The nature of the volcanics and their relationship to iron formation are reviewed. Large-scale outpouring of basic volcanics led to explosive discharge of acid to intermediate volcanic types followe4 by development of iron formation4 Attention is directed to wall rock alteration which occurred largely during development of iron formation. Chemical alteration of volcanics underlying iron formation has been investigated by means of chemical analyses of diamond drill core. Principal chemical changes during alteration were removal of silica, calcium and alkalies and addition of ferrous iron, carbon dioxide and manganese; aluminum and titanium remained essentially constant. Volcanics were considerably altered to a stratigraphic depth of 150 to 200 feet below iron formation; below this depth, alteration was reduced in intensity and of uniform degree. Volcanics underlying iron formation are composed of acid and basic zones, the acid zone lying to the west. The degree and nature of chemical alteration varied someThe acid-basic contact zone, though gradational and what with volcanic type.1 irregular, p1unge eastward at roughly '5 degrees with respect to the present erosion surface. The contact zone may be related to original volcanic f issures or similar linear features. Quantitative determinations indicate that the weights of silica leached from volcanics on the one hand and present in iron formation and ore body on the other, are similar in magnitude. Ore constituents, though, have been added throughout anan outside source is indicated. Possible sources are considered. In general, relations suggest that hot-spring type activity operated during development of iron formation and closed the volcanic cycle. �2]. THE ANIMIKIE SEA / M. W. The great sea from which the Animikian sediments were deposited during the Proterozoic era was responsible for major iron ore deposits of the Canad-' Ian shield. The variations in lithology, minera)ogy and, in some cases, attitude of the beds are due to fades changes and differing metamorphism, not to dif- fering ages of deposition. Periods of orogeny, followed by extensive erosion is the cause of the present localization of the iron-bearing hoZizorLs as opposed to previous postulation that the iron formations were deposited in restticted basins by local, small bodies of water. �22 THE PROPERTIES OF SILICA GEL AND ITS POSSIBLE RELATIONSHIP TO tHE DEVELOPMENT OF LAKE SUPERIOR TYPE IRON ORES Cedric L. Iverson It is assumed that the silica in the iron formations was deposited in the form of hydrous silica ge1. a mixture of polysilicic It is suggested that natural silica gels ave acid and hydrated silicates. Adsorption by silica gel and the effect of pH and the chemical nature of the surrounding medium on this property, is discussed. It is suggested that silica deposited under alkaline conditions will contain adsorbed magnesium, calcium, alumina and, possibly, oxygen while gel deposited under acid conditions may adsorb only alumina and carbonaceous matter. The effects of age, pressure and temperature on the dehydration of these gels are considered.. major factor in dehydration Heat is considered to b the Late stage dehydration reactions consist of the release of hydroxyl ions, oxygen and free electrons. It is considered pos- sible that late stage reactions could result in the formation of hot alkaline cxidizing solutions. It is suggested that solutions derived from silica gels which were laid down under certain restricted conditions, may be capable of oxidizing and leaching the iron theyecape during dehydration formation along the •channelways through which �23 THE ROLE OF INTERSTITIAL AND COMBINED WATERS IN THE DEVELOPMENT OF LAKE SUPERIOR IRON ORES C. H. Spencer, Jr A hypothesis is suggested to explain the leaching of silica from iron formation which may explain the development of some of the Lake Superior iron ores. is suggested that connate waters trapped in the original fine-grained, iron-rich sediments under certain restricted conditions were sufficiently abundant to later form a solvent for part of the silica during diageriesis or metamorphism. The conditons necessary to effect solution of the silica are believed to be moderate emperatures in the range of 100 to 1500 C, and suf- It ficient fracturing of the iron formation to aUow escape of the silica charged waters. Magnesium, hydroxyl, and possibly imentation and released during diagenesis may oxygen ions adsorbed during sedhave furnished reagents which Other products of this breakdown, break down iron minerals to the oxide form. notably alkali bicarbonate, assist in the solution of silica in the channelways along which the escaping waters migrate. The necessary temperatures could be furnished by regional metamorphism, shearing, simple depth of burial or intrusives. Fracturing could be accomplished by all of these forces, possibly including differential rates of compaction. This hypothesi is .distinguished from other ideas on the origin of Lake Superior iron ores in that any set of geologic conditions which will produce the necessary temperatures and fracturing will start the ore-making process in an iron formation with the necessary chemical composition, water content, and geologic environment. �2 THE MINERALOGY, PARAGENESIS AND ORIGIN OF THE CUYUNA SULFIDE DEPOSITS T. N, Han in southThey are normally ovenlain by about O feet of gla- The sulfide deposits are located in south cetitra]. Aitkin and western Canton counties. cial drift,. The depoLts are essentially made up of a sulfide-bearing black slate, composed of qta'rtz, senicite, chlorite, biotite, ilmenite, leucoxene, amorphous carbon, calcite, magnetite, pyrrhoUte, pynite, marcasite with traces of chalcopynite, marmatite, arsenopynite, and antigonite. It is believed that the deposits are a metamorphosed sulfide iron formation of the greenschist facies. They are underlain by and gradational into a thin bedded recrystallized chenty carbonate iron formation. The iron is thought to have been primarily deposited as iron sulfide resembling the pyrite in the black slate of the Iron River-Crystal Falls DisSubsequently, it was subjected to regional metamorphism which led to trict. the formation of pynite and marcasite from pyrrhotite. The conclusions are supported by geographic, stratigraphic, mineralogic and geochemical evidence. Core specimens from thirty drill holes in the area were studied. The paragenesis of the iron sulfide minerals and their relationships are pictorially illustrated. �25 b THE GENESIS OF THE LAKE SIJPERIOR COPPER DEPOSITS* G4 C. Ainstutz The Lake Suprior copper deposits are best explained by a uniform single The field evidence and the microscopic, paragenetic statistical and geochemical analyses lead to the conclusion that the copper is a normal co-magmatic syngenetic constituent accumulated in the hydromagmatic phases of the Lake Superior basalt magma. origin.. First, the copper was brought up in and with the lavas and stayed in the hydromagmatic and hydrothermal portions of th lavas or escaped into the sediments and fractures. After the lavas ceased to extrude, the volatile fractions still continued to leak out from the same magma chambers as hydrothermal fluids, most of which reached the surface and formed the exhalative sedimentary red bed coppers of White Pine, etc.. * (The basis for this paper is experience gained while working for the Bear The author acknowledges the Creek Mining Company in the summer of 1957. Company's permission to publish this paper and emphasizes the fact that opinions expressed therein are his own and not those of the Company.) �26 PEAT RESEARCH AT THE UNIVERSITY OF MINNESOTA Moses Passer About 50 per cent of the United States peat supply is found in Minnesota -- some 7 billion tons in some 7 million acres that comprise about l per cent of the area of the State. With the objective of developing utilization of this resource, the Iron Range Resources and Rehabilitation Commission in l95t established the "Chemical Products from Peat" project at the University of Minnesota. This is a cooperative research project conducted in three departments of the University; Department of Chemical Engineering, Minneapolis Campus Department of Soils, Institute of Agriculture, St. Paul Campus Duluth Branch Department of Chemistry, Duluth Campus The general research activities of these three groups are aimed at de— veloping basic chemical information about peat, its constituents and its derivatives, with the viewpoint of developing chemical. products from peat that may be useful as industrial chemicals and/or in agricultural applications. The project is at Preent engaged in the following areas: (a) Development of processes for preparing high-nitrogen organic fertilizer products nd special amendments for humus—deficient soils. Chemical studies of the products. (b) Agronomic and horticultural evaluation of the experimental soil products. Basic studies of their effects on plants. (c) Fundamental studies of the chemical and physico-chemical nature of peat and its constituents, particularly humic acids Includes functional group analyses, molecular weight studies and solvent-extraction methods. (d) Systematic sampling of Minnesota p.eat bogs. Development of a chemical group analysis for the organic constituents of peat, and analysis of bog samples. (e) Exploratory studies of new and potentially economic chemical applications for peat. (f) A complete survey of the world's literature on peat and related topics has been established in the form of a punched card system. (g) During the summer of 1957, members of the project participated in the "Technical Peat Exchange Mission to the USSR". This mission made a thorough study of the Russian peat industry, visiting their fundamental and applied research laboratories, experimental peat bogs, chemical pilot plants, agricultural experiment stations, and full-scale establishments for the various processes of peat production and its consumption, both as a fuel and for chemical purposes. �27 RECENT SP000MENE DISCOVERIES IN NORTHWESTERN ONTARIO W. L. C. Greer Intensive prospecting following a discovery at Georgia Lake early in 1955 resulted in the finding of at east four major deposits of spodumene. Drilling has indicated reserves in excess of eight million tons, grading 1% Lj20 or better, Most of the showings are in the 1eardmore area. Post—ore diabase sills and dikes have complicated the situation from the mining point of view. production has been had from any deposit as yet. No �28 IRON ORES OF THE PACIFIC NORTHWEST L. C, Binon The existence of iron deposits in the States of Washington, Oregon, Montana and Idaho has long been known. The first use of these ores was as a flux in the smelting of non-ferrous ores. A small iron mining industry has existed intermittently on markets in the non-ferrous smelting, cement and paint industries. Several early attempts to establish an integrated steel industry in the Puget Sound area failed for a number of reasons, one of which The discovery of Precambrian sedimentary was the lack of suitable iron ore. iron formations in eouthwestern Montana and eir preliminary exploration during the past three years by large experienced mining companies indicates that a detailed study of this long-desired goal may now be practical. Fifty or more iron deposits of ten different types are known in the The Precambrian sedimentary iron formation and contact replacement deposits offer the atest immediate economic potential. Large tonnages of ferruginous laterite and titaniferous beach sand ores are available but the complex metallurgy has retarded their development. Ferruginous schists and siderites of sedimentary origin, bog ores, massive sulfide deposits and aSssociated gossans, and veins of primary iron oxide have all been explored or considered as resources for the production of metallic iron. Occurrences of each type are described, together with an evaluation of their economic potenarea. tial. �29 CHARACTERISTICS OF SOME IRON—BEARING FORMATIONS IN NORTHERN WISCONSIN E. L. Beutner Increased. interest in lean ores during recent years has led to re-examination of drift-covered areas in northern Wisconsin where magnetic anomalies had indicated the presence of iron-bearing rocks but here little, direct geological information was available. Exploration drilling was done at Magnetic Center in Iron County and near Butternut, and in Agenda Township in Ashland County. The characteristics of the iron formations and related rocks are described. It is suggested that the sedimentary and volcanic environments in which certain Middle and Upper Huronian sediments were deposited in the East Gogebic Range area also existed to the south and west in Wisconsin. While part of the iron bearing sequence resembles the typical banded cherty iron foniations of the better known ranges, there is also much material which, while iron bearing, contains little welldefined chert. The presence of abundant other minerals such as chlorite and mica seems to indicate that mud, possibly of volcanic origin, as well as silica, was being deposited with the iron-bearing sediments here. The rnagnetite-grünerite iron formation and black slate association in Agenda Township closely resembles the metamorphosed Upper Huronian Bijiki formation on the Marquette Range. �30 RECENT IRON FINDS IN NORTHWESTERN ONTARIO E. R. Mead Modern beneficiation techniques have changed the economic outlook for low grade iron deposits in the Canadian Shield. iron Most of the previously kncwn formations have been staked and inten prospecting has led to many new discoveries, The occurrences are discussed in belts groups according to the sedimentary in which they lie.. Studies of the new finds and their enclosing se- quences should throw new light on the complicate1 stratigraphy of the area1 �UNIVERSITY MINNESOTA Cohtiiuation Study of the General Extension Division . Center for Minneapolis il'. InstItute on April 21 - 22, 1958 Lake Superior Geology Registrants Aase, James H. 207 Christie Building Duluth, Minnesota Mair, Donald L. 2230 East Second Street Duluth, Minnesota Amborn, Ivan 2202 Ogden Avenue Superior, Wisconsin Amstutz, G, Chris Department of Geology. Rolla, Missouri Anderson, Cleveland-Cliffs Iron Company Ishpeming, Michigan 1958. Gerald J. Anderson, Jule R. 107 West Lincoln Avenue Tomahawk, Wisconsin Avery, John U. 551i. Jasper ail1y, Paul A. 3361 Republic Avenue Minneapolis 26,.Minnesota Bakkila, .Bartley, Henry N. U. Street Ishpeming, Michigan 11121 South Twelfth Street Virginia, Minnesota 213 Park Street Port Arthur, Ontario, Canada Bath, Gordon D. k Homevood. Place Menlo Park,. California Bayley, Richard. W. U. S. Geological Survey Homewood Place Menlo Park, California Beckman, Charles A. 635 Belobraidich, William Bennett, Hugh F, 1950 Erie Street Southeast Minneapolis lL, Minnesota 723 Sixth Avenue East Grand Rapids, Minnesota Geophysic Department University of Wisconsin Madison 6, Wisconsin 1957 �-2- Lake Superior Geology Beutner, E. L. Jones and. Laughlin Steel Corporation #3 Gateway Center Pittsburgh, Pennsylvania 1957 i6io P. 0. Build.ing Bingham, Janice W. St. Paul 1, Minnesota 1950 Binon, Layton C. Northern Pacific Railway Company St. Paul, Minnesota Bleifuss, B. L. 11r832 Grand. Avenue. Duluth, Minnesota Boyce, Forrest U 11.31 Arlington Roa& Hoyt Boyuni, Burton H. Brernner, .Peter C. 1952 . Lakes, Minnesota 1952 Cleveland-Cliffs Iron Company 1911.1 Ishpeming, Michigan The North Bay Ontario, Canada. Broderick, Alan T. 805 Maurice Isbpeming, Michigan Brinley, Edward. H. 276 North Cumberland. Street Port Arthur, Ontario, Canada Bryan, Russell B.,. Jr. Burgan, Edward C. Burns, B. D. Dyers, Richard. R. Calainan, Joseph 1209 DeYoung Building San Francisco, Qalifornia 239 Bolsam Port Arthur, Ontario, Canada Stanleigh Uranium Elliot Lake) Ontario, Canada 610 Wolvin Building Duluth, Minnesota Box 173 Aurora, Minnesota Cameron, Eugene N. University of Wisconsin. Madison, Wisconsin Campbell, Vernon B. Box 521 Eveleth, Chapman, Rodger H, Minnesot.a 14.0 East 850 South Orem, Utah j Childs, Tappan (Mrs.) 1950 920 East Twenty-first Street Hibbing,. Minnesota 1930 �Lake Suoeior Geology Cotter, Ralph D. -3- i6io P. 0. Building St. Paul 1, Minnesota. Duhling, William N., Jr. 2113 Sixth Avenue East Hibbing, Minnesota Durfee, George A. Box 75 Dutton, Carl E. U. S. Geological Survey Eveleth, Minnesota Madison Effinger, FrederIck D. 1951 6, Wisconsin 14111, North Eighteenth Avenue East Duluth, Minnesota Everett, Jack V. 5325 Otsego Duluth, Minnesota Fegan, 2323- Second Avenue West Hibbing, Minnesota James A. Fetzer, Wa-ilace 1. 14692 West 227th Street Cleveland., Ohio Forbes, Box 711.3 Peter C Wakefield, Michigan Fritts, John 3. white Pine Copper Company White Pine, Michigan 1957 Gair, Jacob E. U. S. Geological Survey Denver, Colorado Gauvin, Jacques Steep Rock Iron Mines Canada Gehnian, Harry M. 3529 East Independence Street 1957 Tulsa, Oklahoma Gulls, Ronald N. 302 West Second Street Duluth Goodwin, A. N. 2, Minnesota Jamestown Canada Ontario, Greer, W. L. .C. 213 Park Street Port Arthur, Ontario, Canada Gross, G. A. eo1ogica1 Survey of Canada Ottawa, Canada Hakala, Harvey J. 5600 London Road. Duluth, Minnesota Rardenberg, Harry J. Michigan Geological Survey Lansing, Michigan 1957 �LakSuDerior Geology Geology Depa'tment Ease, Donald H. State University of Iowa Iowa City, Iowa Heising, Leonard F. Hoppin, Richard A. 1701 Merrrview Lane Ribbing, 1958 Minnesota Geology Department State University of Iowa Iowa City, Iowa Euedepohi, E. B. koO West Madison Illinois' Chicago, Eustad, James B. 616 Wolvin Building 1958 Duluth 2, Minnesota Iverson, Cedric L. 5113 London Road Duluth, Minnesota Jahren, Charles E. 810 Neola Austin, Minnesota Jaksa, Frank Anthony Jensen, Frederick 19)4.9 808 Adams Avenue Eveleth, 1956 Minnesota 370 Third Avenue South Park Falls, Wisconsin, Kelly, 1i11iam. C. 212k Brockrnan Boulevard Ann Arbor, Michigan Kisvarsanyi, Geza Box 631 Aurora, Klinger, P.. L. 521 Eleventh Street North Virginia, Minnesota Koebler, George P. .197 1958 Minnesota 215 Park Street Port Arthur, Ontario, Canada Kral,. Victor E. 1011 North Stephenson Avenue Iron Mountain, Michigan Kundert, Karl H. P. 0. Box ii6, Duluth 7, West Duluth Station Minnesota Leone, Ray J. White Pine Copper Company Lindgren, Donald W. Northern Pacific Railway Company St. Paul, Minnesota Lubker, Robert White Pine, Michigan E. 1728 Huliview Road Minneapolis 21, Minnesota 1957 �Lake Superior Geology Lucas, Raymond C. MacIntosh, A. N, -.5-. 6o. First Avenue Northtest Chisholni, MinnesOta 1957 Michigan College of Mining and. Technology Houghton, Michigan Mancuso, JamesD. Box 631 Aurora, Marsden, Ralph W. Mead, E. R Nillett, Frank Minnesota 6io Wolvin Building Duluth, Minnesota 213 Park Street Port Arthur, Ontario, Canada B., Jr. 1955 3361 Republic Avenue Minueapoli, Minnesota Moerlein, George A. Box 7.2 Mellen, Wisconsin Moore, G. Neely 215 Park Street Port Arthur, Ontario, Canada Moyle, Robert N. 1.032 Robinson Street Duluth, Minnesota Nunter, Yaziner J Eveleth Fee Office, Box 521 Eveleth, Minnesota Mutch, A. D. Falconbridge 1927 Canada Nielsen, Richard Box 606 Mellen, Wisconsin Neilson, J. N. Houghton, Michigan Niles, Harlan B. 917 North Fourteenth Avenue East Duluth, Minnesota Ohie, Ernest L Copper Range Company White Pine, Michigan Orsboro, J. T. 130 Laurie Street Duluth, Minnesota Ostenso, Ned 1950 1957 Geophysics Department University of Wis cons in Madison Owens, John S. 6, Wisconsin Ozark Ore Company Iron Mountain, Missouri 1953 �-6- Lake Simerior Geology palmer, Harris A.. Wisconsin Paulson, H. K. 300 Wolvin Building Duluth, Minnesota- Institute of Technology Platteville, Wisconsin l98 Plumer, Wayne L. 35 Fraser Location Chisho.m, Minnesota Potapoff, P. Falconbridge Ontario, Canada Randolph, B. Richard P. 0. Box I5 Taconite, Minnesota Reaa) William F. Geology Department, Lawrence College Appleton, Wisconsin Reed, Robert 522 Sunrise Court East Lansing, Michigan Reid 5115 Wyoming Street Duluth 14, Minnesota I. L.. Riedel, RobertWRichard Riord.an, . 198 Shuniab Port Arthur, Box 1 Deen'ood, Roberts, Hugh N. 306 Street. Ontario, Canada -Minnesota Lonsdale Building Duluth 2, Minnesota - Rogers, James B. i6io Post Office Building St. Paul, Minnesota Romanuck, Morley S. 1400 Torrey Building Duluth, Minnesota. Royce, J. Pickands, Sadler,. J. Mathers.& Company Duluth, Minnesota Steep Rock Iron Mines Steep Rock Lake, OntarIo, Canada F. Deerwood, Minnesota Sarja, Henry Schmidt, Robert Schwartz, G. G. M. Scofield, Lloyd N., Route 1, Box 19 Lanham, Maryland 237 Bedford Street Southeast nn, Minnesota 14020 Gladstone Street Duluth 14, Minnesota �take Su'erior Geology Sevensma, Pieter II. Slaughter,. Arthur E. 215 Park Street Port Arthur, Ontario, 1111 South Sixteenth Street Escanaba, Sneigrave, A • K, Canada Michigan. Houghton, Niciligan Spencer, George H, Jr., 3512 East Fourth Street Duluth, Minnesota Spiroff, Kiril Michigan College of Mining and Technology Houghton, Michigan Stephenson, 'Thomas E. • Strong, 329 Sixth Street South Virginia, Minnesota Box 126 Crosby, Minnesota Richard Terrel, Ronald L. '3361 Republic Avenue• Minneapolis, Miflnesota Thiel, Edward 2930 University Avenue Madison, Wis cons in Street Torreano, August F. 21.l1 East Fourth Duluth, .Minnesota Torreano, Peter F. Merideü Iron Company. Ribbing, Minnesota Trost, Lawrence C. M. A. rianna Company Crosby, Trow, James Minnesota 2700 Woodruff Avenue Lansing 12, Michigan Tusa, James E. Ishpemlng, Michigan Wade, Henry H. University of Minnesota Mines Experiment Station S Walker, 1958 Harry.C. Minneapolis 14, l955 Minnesota 1915 P.. 0. Box 116, West Duluth Station 1958 Duluth 7, Minnesota • Wier, Kenneth L. Wolff, J. F., Sr. Iron Mountain, Michigan 1515 Vermilion Road Duluth, Minnesota �1 S'Iollenzien, Thomas Peter 719 Great Northern Building St. Paul 1, Minnesota Wverch, U. V. YarcUey, D 1958 216 Second Street Northwest Crosby, Minnesota H 2107 Fairways Lane St. Paul, Minnesota Students Banks, Tom University of Minnesota. Blake, Roland. L. University of Minnesota Buchheit, Richard University Gindzwill, Don Michigan Inztltute of Thnology of Minnesota Gunderson, James in Hendrix, Thomas ti1S COflS Herubin, Robert University of Minnesota Hudson, Iowa' Robert F. State University Johnson, David University of Minnesota Krueger,. University of Minnesota Harold. W. Quirke, Terence T.., Sargent, Kenneth A.. Sato, Ftotoaki Jr. University of Minnesota Iowa 211 Warwick Southeast Minneapolis 1k, Minnesota Scheerer, Paul Wisconsin Trent, Virgil A. 6887 Minock Street Detroit 28, Michigan iihe Ian, James A. Williams, Lyman Gruner, John W. University of Minnesota 0. Iowa State University Iowa State University � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1958 Description An account of the resource Proceedings of the Institute on Lake Superior Geology. University of Minnnesota, Duluth, Minnesota. April 21-22, 1958. Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1958 Format The file format, physical medium, or dimensions of the resource PDF https://digitalcollections.lakeheadu.ca/files/original/1135262d1a5298d29e3c363c4105c2ed.pdf 63c696da89ec3e7d6be8893811b37078 PDF Text Text FTh'PH ANNUAL MEETING INSTITUTE ON LA1 SUPERIOR GEOLOGY April 13 - lIe, 1959 UNIVERSITY OP MINNESOTA Center for Continuation Study of the General Exteneton Division Minneapolis lie �TAJE OF OF CONTENTS CONTENTS Page i. i ii CempuB Buildings Map of CamPUS Parking Facilities FacilitieB Map of CaInPUB Campus Parking 1 Progrwn Program 33 LiBt List 17 of Speakera Speakers Hydrothermal and The Genetic Genetic Meaning Meaning of of the the TerniB Terms Hydrothermal ..... ....,.. Replacement.. .. 2]. • .. . .. .. .. .. .. . . ... ... s1•S .G. CC. • AB1BtUtZ Amstutz in West-Central WeBt-Central Geomorphology in Current Research ReBearch in Glacial Geology and Geomorphology F. Black .•.•••.• ......• ,•, . .... ... .....Robert •1I .Robert F. Wiaconsin..........o. o....o... . 0.. o... e5SGSSG•SS WiBconBin. .. . ..••. .os ai 6 Geology ofof the the Greenwood Mine - Mine - A Hard Ore Producer on the Greenwood The Geology .Alan T. Broderick MarQuette . .. ..,....... .•..•. . MarQuette Range, Range,Micbigan.. Michigan..... 18 H.Dott, Dott, Jr. Jr. Tillite orSubaqueOuB Slide2,..........u.............c..R. H. 25 The The Geology Geology and and S 5 Electromagnetic ..,.......• .••. DepoBitB of the Mount Wright Map Area, Quebec Iron Deposits Duffell •II...S •S •• Duffell ,, ,... SD C ... ••, .. .. .. ... .,• Canada....,..... Canada.... Newfoundland, • Nefodld, ••• ..••.•• . s..... Studies of the Lake Superior Iron RangeB..................c......e.....sF. C. FriBchknecht, E. Ekren Ranges.,.....,,..........c..o..,e.....sF.C.Fri8cfleCht, E. B. B.Ekren 88 AgeB in in the the Northern Northern Cordilleran Cordilleran Region.........PaUl Region........Paul W. W. Gast GaBt precambrian Ages Precambrian 10 Summary of Radioactivity Radioactivity Dating Dating of of the the Precambrian Precwnbrian Rocks Rocks of of Summary of' S. Goldich, A. 0. Nier 2k ProblemB Problems in Northern New England Stratigraphy.....e.,......Johfl Stratigraphy.....e..s.....Johfl C. Green 11 Application of the the Gravity Gravity Method Method to to Iron Iron Ore Ore Exploration....W. Exploration...W. 7. J. Hinze Hinze 7 InveBtigationa Investigations in the Precambrian of the Bighorn Mountains, Mou2tainB, Wyoming..,..................R. A. Hoppin, R. F. Hudson, Wyoming.....................R. Hudeon, K. A. Sargent Origin of Iron Formation...,...............HeflrY Formation,..,,.....,........Henry Lepp 1k The Chemistry ChemiBtry and 27 Structural Structural StudieB Studies in in the the Thom8on Thomson Formation, Formation, Carlton Canton County, County, ,,• • . . .5 MinneBota... ..,,,, ..... . , .•. ,,. ••,•• Minnesota... , .1,Louis ,LouiB •• ...... ...• , . . Mattaon A. Mattson 23 Mineral Exploration Exploration in in Southern Southern Baff Baff in in Island, Island,N.W.T...,JanleB N.W.T....James M. M. Neil8on Neilson 9 Use of Precambrian Precambrian Calcareous CalcareouB Alga]. Algal. Colonia Colonia as a IndicatorB Indicators PoBBible UBe Possible C •• Nordeng £tephan C Nordeng •. . ... .£tephan ,, •• , .. Polar Shifts.. BhiftB........ of Polar ..... . Is•••• . . . ••. ••••• e e s o..,...... �TABLE OF CONTENTS (Continued) Page 19 Geology of the Iron Formation Occurrence Near Keminietikwia, John M. lvi. Ohison Ohlson .. , .• ., • . ..,1John .. . .. .e••, . . . . . ,.... . . . . ,,,.1 . • ., •. Ontario. .. . 11*..... Ontario.... . • . . .. . . .. . . .. 22 Geology of of the the Lake Lake Albanel Albanel Iron Iron Range, Iane, Nistasaini Nistasaini Territory, Territory, Jr. Quirke, Jr. ,Terence Quebec....o..,.................o..s......,....o.TerenCe T. T • Quirke, Quebec... . 12 F. Read Read Geochemical Sampling Sampling of of Lake Lake Bottoms Bottoms in in Winter...,...,..William Winter..,,...,..William F. 26 E. Sloan Sloan The Cretaceous System System of of Ninnesota..00•...,..0•.,..i,o...Iobert Minnesota.00•......0•.,..i,....Robert E. 13 13 M. Swain Swain Amino Acid Acid Distribution Distribution in Lake Deposits..........,..FrederiCk Deposits.,....,..,..Frederick 14. Amino .. .. .. ,•,, ,, ,... . , . . .. • . . .,• • . . . 1 l The Petrogenetic and Economic Implications of the Quantitative Mineralogical Variation Within a Large Granite Complex... Complex. .. .. .. . . . ..... .. . . . .., , . ..... , . .. . ... .E. .E. H. Timothy Whitten ., . . ..,. ......... .. . . .... 20 20 Pleistocene Pollen .fl. E. E. Wright, Wright, Jr., jr., Magnus Magzus Fries Pleistocene Pollen Studies Studies in in Minnesota. Minnesota..H. Fries �\ \\\ S S / p P I R IV ER �I. •IIIIs 1 MINNEAPOLIS CAMPUS PARKING FACILITIES •I C9 096 4— C25 L C - CR3 REA RE NOVEMBER 195B, NOVEMBER 1958, REVISION REVISION CONTRACT PARKING MPLS-ST PAUL BUS ROUTE BUS STOP PARKING LOT -- LOT ENTRANCE $d **V #ItI? �1 OF MINNESOTA MflNESOTA UNIVERSITY OF Center for Continuation Study of the GenerE1 Extension General Extension Division Division 1I Minneapolis l4 Institute on on Lake Lake Institute 114, 1959 April 13 - 14, Superior Superr_Geo]9 Geolo PROGRAM Monday, April 13, 1959 8:00 - Registration 8:"5 8:45 and coffee hour, Center for Continuation Study end SESSION I** Room 14, Room 4, MechLnical Engineering Building Co-Chairmen: E. N. Cameron, Richard A. Hoppin toOrder.....,......,.,......D..........,..,..,...F1'edE. Berger 9:00 Call toOrder.....................D...........,..e..,...FzedE. . . . . . . . . . . . . . .George A. Thiel 9:10 Welcome. . ,................... ...... . OF THE LAKE SUPERIOR ON STUDIES OF ELECTROMPGNETIC STUDIES 9:25 ELECTROMAGNETIC . . . . .. . . . . . •1 , • • . . . . .F. Frischknecht, E. B. Ekren* RANGES. . ORE PRODUCER ON TBE PRODUCER ON THE HARD ORE GREEI'WOODMINE MThE -- A HAR]) 9:50 THE GEOLOGY OF THE GREENWOOD 9 5O ... .. . 10:15 MABQUETrERpNGE,MICuIGAN,,.e........o..s.......AlanT.Broderick MARQUETTE RANGE, MICHIGAN,,.,.,...,....,,....,....A1anT. Broderick INVESTIGATIONS IN OFTHE THE BIGHORN BIGHORN )UNTAINS, PRECAMBRIAN OF INTHE TI PRECAMBRIAN A. Sargent A. Hoppin, Hoppin, R. R. F. F.Hudson*, Hudson*, K. K A. Sargent R P. WYOMING NORTHERNCORDULERPN CORDELLERPN REGION,......PaU1W. W.Gast Gast 10:140 ECAJv1BRIANAGES AGESIN INTHE TI NORTHERN REGION,...ae.Paul 10:40 PRECAMBRIAN CALCP1REOUS ALGAL ALGAL COLON IA AS POSSIBLEUSE USEOF OFPRECAMBRIAN PRECANIPsI' CALCP1REOUS COLONIA AS INDICATORS 11:00 POSSIBLE 11:00 Step in C. C. Nordeng Nordeng POLAR 5HIFTS ,s..s. •, •. OF POLAR SUI'1WRY OF OFRADIOACTIVITY RADIOACTIVITY DATJiG DATINGOF OFTKE THE PRECAMBRIAN PRECAMBRIAN ROCKE ROCKS OF OF 11:25 SUMMARY A. 0. 0.Nier Nier MNE3OTA,.,...,.oo..,,,.....o.o.g.......,S,S. Goldich*, S. Goldich*,A. 12:00 Luncheon, Center for Continuation Study 12:00 ..,.. ... ..,.. .. •. SESSION II SESSION 4, Mechanical Room Mechanical Engineering Building Room 14, Marsden, James Trow Co-Chairmen: Ralph W. Mareden, Hinze .W. 3. 3. flinze V1ETEOD TO IRON ORE ORE EXPLORATION. EXPLORATION. .W. 1:30 APPLICATION OF THE GRAVITY METHOD F. Read WINTER0 LAKE BOT'rOMS BOT'IO! IN WINTER........,William 2:00 GEOCHEMICAL SAMPLING SA!PLING OF LAKE 2:00 GEOCHEMICAL DEPOSITS......3....Frederick M. Swain 2:25 AMINO ACID DISThIBUTION DISTRIBUTION IN LAKE DEPOSITS......,.....Frederick 2:50 Coffee Break ORIGfl OF OF IRON IRON FORMATION..,. FORMATION..,.,e..u.......sflenry o e . . .... .. .. .Henry Lepp 3:20 THE CHEMISTRY AND ORIGIN IMPLICATIONS OF THE QUANTITATIVE A1D AND ECONOMIC THE PETROGENETIC 3:45 3:145 LARGE GRANITE GRANITE MINERALOGICAL VARIATION WITHIN A LPIRGE H. Timothy Timothy Whi Whitten tten ,. ... ..E. .E • H. • •. • •• 10 COMPLEX. COI4PLEX. o . cc ore , • eS . ••S e • e . cc eeo AND 4:10 THE THE TERMS HYDROTHERMAL 14:10 TI GENETIC OF T TERMS HYDBOTHMAL GENETIC ?ANING MEANING C, .Amstutz Amstutz REPLACENENT..,cc,ac.c.,.sos....,o,ab,.eo..soG,..I...cG. • .. .. . .G. Ce REPLACEMENT.., • • • . 1013 bIle OS 110 , junior Ballroom, Third Floor, Coffman Memorial Union Building 6:30 Dinner, \inior Presiding: Donald M Davidson Donald M. Davidson Speaker: John W. Gruner "140 YEARS IN COLD "40 YEARS Topic: COLD AND MD HOT HOT WATER" WATER" .......William •., S •. .•• * ** * Indicates Speaker Five minutes for discussion diecussion are allowed after each paper, throughout the program the �Lake Superior Geology 2 Tuesday, April Tuesday, April ].14l959 lI,l959 III SESSION SESSION III Room 14, Mechanical Engineering Building Eo Dutton Co-Chairmen: Jack L. Hough, Carl B0 Co-Chairmen: 9:00 9:25 9:145 10:10 10:10 lO;30 10 :30 H. Dott, Dott, 31. Jr. TflLITE OR TflJLITE OR SUBtQUEOUS SUBAQUEOUS SLIDE?.*....o............i....i..R. H. KAMINISTIKWIA, GEOLOGY OF THE TEE ON FORMATION OCCURRENCE NEAR KANINISTIKWIA, Ohlaon M. Ohison , ... ,,John ,John M. c..s.s . . . .ci. e... •. •a. .o . . . , •• ..o.o. . . so....•.. ONTARIO. .... .... css ,, s.o.s.... Wright, Jr.*, MINNESOTA.........0..H. H. Wright, Jr.*, PLEISTOCENE POLLEN IN IN PLEISTOCENE POLLENSTUDIES STUDIES MINNESOTA........0..H. E. Magnus MagnusFriea Fries Coffee Break Break Coffee INWEST-CENTRAL WEST-CENTRAL GEOLOGY AND GEOMDRPHOLOGY CURRENT RESEARCHIN INGLACIAL GLAC IAL GEOLOGY AND GEORPHOLOGY IN CURRENT RESEARCH F. Black Black F. RANGE,MISTASSDU MISTASSINI LI ALBMIEL lO:O GEOLOGY GEOLOGY OF OFTHE THELANE 10:50 ALBANELIRON INONRANGE, Quirke,Jr. Jr. TERRITORY, QUEBEC..u,..,,...os,po.3..c..c....oTerenceT. QUEBEC,.,,.,,,,......0•3.......,.0TerenceT.Quirke, TERRITORY, BAFFINISLAND,N,W0T...Janies ISLAD,N.WT..James M. SOUTHERN BAFFIN M. Neileon Neilson MDERMJ EXPLORATION IN SOUTHERN 11:15 MINERAL Center for for Continuation Luncheon, Center Continuation Study Study 12:00 Luncheon, SESSION IV 14 Mechanical Engineering Building Room 14, Co-Chairuien Cedric L. Iverson, Ivereon, Donald W. Lindgren Co-Chairmen: 1:30 PROBLE1 PROBLE1 ININ NORTHERN NORTHERN NEW 1:30 NEW ENGLAID ENGLAND STRATIGRAPHY..,s..e..e.oJohn STRATIGRAPHY..., lie . . .0John CC.• Green 1 :55 DEPOSITS OF WRIGHT MAP MAP AREA, 1:55 THE THE GEOLOGY OFTILE TILE4JUNT UNT WRIGHT GEOLOGY ANDON ON DEPOSITS NEFOUDLAIqD,CANADA.c.,.,......,.,,.ç.0...t,..S,Duffell QUEBEC NEWFOUNDLAND,CANADA.cca...............c.ee...e..S.Duffell 2:20 2:20 T] SYSM OF MINNESOTA.0...........,....,Robert MINNESOTA.0.,..........,....,Robert E. E. Sloan Sloan THE CRETACEOUS CRETACEOUS SYSTEM 2:145 FORMATION, CARL'ION STRUCTURAL STUDIES CARLTON COUNTY, STRUCTURAL SIUDIES IN COUNTY, IN THE ThOVEON FORMATION, MINNESOTA. . .. MINNESOTA. .. • ..... ,1 •.• . . . .. ...... I•I •,. ,•. •. .• .. s...., .. .., ,• ... . .. .. .,.. .. . .Louls .Louis AA •• Mattson M * * Indicates Speaker Speaker SPEANERS SPEAKEBS G. C. C. AlTUTZ0................Departxnent AlTUTZ0................Departxnent of of Geology, Miseouri G. Geology, MissouriSchool School of ofMinea, Mines, Rolla, Rolla, Miseouri Missouri FRED FRED E,B, BERGER..,,..........Director, BERGER..,...,,,....Director,Center Centerfor for Continuation Continuation Study, University of University ofMinneBota, Minnesota, Minneapolia, Minneapolis, Minnesota Minnesota ROBERT F. ROBERT F. BLACK........,..oa.oDepartment Wisconsin, BLACK,......,...c.oDepartfllent of of Geology, Geology, Univer8ity of Wisconsin, Madiaon, Wisconsin Wi8consin Madison, ALAN T. T. BRODERICK,.5........,,Chlef BRODERICK,.,,.,..,,,Chlef Geologiat, Geologist,Inland Inland Steel Steel Company, Company, Iahpeming, Ishpeming, Michigan EUGENE N. CAMERON..,.,,,,..,,professor EUGENE CAI4ERON....,........Profeaaor and and Head, Department Department of of Geology, Geology, Univeraity of Wisconsin, University Wiaconain, Madison, Wisconsin Wisconain DONALD M, DAVIDSON.,.,..,,.,.Preeident, Longyear Company, DAVIDSON.,,....,,...President, B. E. JJ Longyear Company, Minneapolis, Minneapolia, Minneaota Minnesota ROBERT H. DOPr, ....,.Departnient of Geology, University of Wisconsin, Wiaconain, Madison, Wisconsin STANLEY DUFFELL......0.50.,...Geologjcal DUFFELL.. . Survey Survey of of Canada, Canada, Ottawa, Ottawa, Ontario Ontario CARL B. E. DUTTON...............Regional Geologist, Geologiat, U. U. S. S. Geological Geological Survey, Madiaon, Wisconsin Wisconain Madison, E. B. B. EI{EN......eo..oe...,s..Qeophysics EI{EN...s..eo...,,....Geophysics Branch, S Geological B. Branch, U S. Geological Survey, Survey, Federal Center, Center, Denver, Denver, Colorado Colorado H. DOTT, ....,.Department of .. .. . ....Geological �Lake Superior Geology SPEAIRS SPEAKERS (Continued) MAGNUS FRIES..................Research A880ciate, MAGNUS FRIES..................Research Associate, Department Department of Geology, University of Minnesota, Minneapolis, MinneapoliB, Minnesota FRANK FRISCHKTTECHT.....,.....Geophysics FRISCHKNECHT......,.....Geophysics Branch, Branch, U. S. Geological Survey, Survey, U. S. Federal Center, Denver, Denver, Colorado Colorado PAUL PAUL W. W. GAST............. GAST.................Aaeietant ....Aaeietant Profeesor, Professor, Department Department of of Geology, Geology, University of Minnesota, Minneapolis, Minnesota SAMUEL S. SAMUEL S. GOLDICH.......,.,..Profe8eor, GOLDICH...........Professor, Departznent Department of of Geology, Geology, University of of Minnesota, Minneapolis, Minnesota Minneeota JO C.C,GREEN...............,.Department JOHN GREEN................Departznent of of Geology, Geology, Univereity University of Minnesota, Minnesota, Duluth, Minziesota Minnesota Duluth, JOHN GRUNER...,............Profeseor, Department JOUN W. GRtJNER...,..........,,Professor, Department of of Geology, Geology, University University of of Minnesota, Minneapolis, Minnesota W. J. HmZE................,..Aeeistant HmZE.............,.,..,Assistant Professor, Profes$or, Department of Geology, Michigan State University, East Lansing, Michigan RICHARD A. HOPPIN............Department of Geology, State University of Iowa, Iowa City, Iowa JACK L, L. of of Geology, Geology, University University of of Illinois, Illinois, Urbana, Illinois R. F, flJDSON,,.,....,,..,.,...Graduate HUDSON........,...,.,,.,Graduate Student, B. Student, Department Department of of Geology, Geology, State State University of Iowa, Iowa City, Iowa CEDRIC L. IVERSON.........,..,Oliver IVERSON....,...,,..0Oliver Iron Mining Division, U. S. Steel Corporation, Duluth, Minnesota HENRY LEPP......)..o..,......Aseociate Professor, Professor, Department Department of of Geology, University of Minnesota, Duluth, Minnesota DONALD W. LINDGREN.........,..Chlef LINDGREN.......,,,..Chief Mining Geologist, Northern Pacific Railway Company, St. Paul, Minnesota RALPH W. ....., ,... ..Manager, Geological W. MARSDEN.. MARSDEN......,......Manager, Geological Investigations, Investigations, Oliver Oliver Iron Iron Mining Division, U. S. Steel Corporation, Duluth, Minnesota LOUIS A. A, MATTSON,,..,....,,,..Graduate MATTSON,.....,.,.,...Graduate Student, Department of Geology, University of University of Minnesota, Minnesota, Minneapolis, Minneapol1, Minneaota Minnesota JAMES M. NEILSON.........,....Department NEILSON..,e...e.,,...Department of Geology, Michigan College of Mining and Technology, Houghton, Michigan ALFRED 0. NIER................Head, School of of PhyBics, Physics, University University of of Minnesota, Minnesota, NIER.o..........,,.Head, School Minneapolis, Minnesota 7. N. M. NOLPE..................Deari, NOLPE........,,0,.......Dean, General Extension J, Extension DiviBion, Division, University University of of Minnesota, Minneapolis, Minnesota Minneaota STEPRAN C. STEPHAN C. NORDENG.......,...,Assjstant Professor, Department Department of of Geology, NORDENG,..,.,,..,,As9istant Professor, Geology, Michigan College of Mining and Technology, Houghton, Michigan JOHN M. O}ILSON...,,.o..o,.....Asejstant O}ILSON.o..,.o..o......Assistant Geologist, Inland Steel Steel Company, Iron River, Michigan TERENCE T, QUIRKE, JRe.......Assistant JRc....,..Asaistant Professor, Department of Geology, Fork3, University of North Dakota, Grand Forks, North Dakota W, F, F. READ...,.....,....,,,.,Department READ......,.,.....,.,.Department of of Geology, Geology, Lawrence College, Appleton, Appleton, Wisconsin Wisconsin K. K. A, A, SARGENT...g,....,.,...,,State S.ARGENT..,go....g.,,..,State University University of of Iowa, Iowa City, Iowa ROBERT E, ROBERT , SLOAN....., SLOAN.o........,.oAasistant ....,... .Assistant Professor, Department of Geology, University of University of Minnesota, Minnesota, Minneapol1.s Minneapolis Minnesota Minnesota �4. 4 Superior Geology Lake Superior SPEAKERS(Continued) (Continued) SPEAKERS F, M. SWAIN..,.e.,,,.,.e...oe.PIOfeSGOr, SWAIN.e..e...,.,.e...oe.P1OfeSSOr, Department of Geology, University of Minnesota, Minneapolis, Minnesota and Chairman, Department GEORGE A, Department of of Geology, Geology, A. THIEL...............Professor THIEL..............Professor and University of Minnesota, Minneapolis, Minnesota TROW. ................ ..Department of Geology, Michigan State University, JAI4ES JAMES TROW....................Departnlerlt East Lansing, Michigan E. H. H, T, WHITPEN..,...........Departnent WHITPEN.............Department of of Geology, Geology, Northwestern Northwestern University, University, Evanston, Illinois JR...,.,.......Associate Profes8or, H. E. WRIGHT, JR....,,,,..,...Associate Professor,Departixent Department of Geology, University of Minnesota, Minneapolis, Minneapolia, Minnesota �5 ELECTROMAGNETIC STUDIES OF THE LAKE SUPERIOR IRON RANGES F. C. Frischkneoht and E. B. Ekren U. S. Geological Survey, Denver, Colorado In the past two years the U. S. Geological Survey has made experimental electromagnetic studies over several of the iron ranges in the Lake Superior region. The three principal objectives were to evaluate electromagnetic methods as a tool for locating directly oxidized iron ores, to test electromagnetic methods of tracing taconites that are known to have high electrical conductivity, and to determine if electromagnetic methods could be used to estimate the magnetic susceptibility and magnetite content of magnetic strata. In the areas tested in the Cuyuna range it was not possible to locate directly oxidized iron ore beneath the 90 feet of drift present. It was possible to trace the contact of the hanging—wall and iron formation by following a graphitic or other conducting bed along the contact. In the Gogebic range individual members of the iron formation were traced as conductors by conventional electromagnetic methods. The foot-wall quartzite and iron formation contact was readily located, but the hanging—wall iron formation and slate contact was difficult to locate because of conducting strata within the slates. Unless special electromagnetic techniques were used, some drilling control was necessary to define accurately the hanging wall contact of the iron formation. A variable-frequency electromagnetic technique, which was tried on the Gogebic range, showed promise as a practical method for distinguishing between tacoriite, which has high electrical conductivity and high magnetic susceptibility, and graphite, which has high electrical conductivity, but low susceptibility. The same variable-frequency technique was also useful in estimating the magnetic susceptibility and magnetite content of magnetic strata. �6 THE GEOLOGY OF THE GREENWOOD MINE -- A HtBD ORE PRODUCEII ON THE MARQUTTE RANGE, MICHIGAN Alan T. Broderick Inland Steel Company, Ishpeming, Michigan The Greenwood Mine has been a small but steady producer of specularite and magnetite lump ores since 1932, The total production to date has been about two million tons, this ore has come from relatively small, discontinuous bodies which lie in the 1ieinatite-chert facies at the top of the Negaunee iron formation and in the bottom of the overlying Goodrich conglomerate. The The formation strikes east-west and dips about 70 degrees to the north, the garnet zone of metamorphism. rocks are in All of as Structurally, the ore bodies are found in three environments: contact with the Goodrich conglomerate; wall irregular sheets along the hanging as irregular, steeply dipping, rudely tabular masses ("droppers" in the local mine terminology) and as irregular pipes that follow inverted troughs formed by folds or by the intersections of faults and/or dikes and the hanging wall. In textural and mineralogical detail, there are four distinct end member types of ore: conglomerate, i.e. pebble and sand-bearing hematite; "slaty1', i.e. fine-grained, finely laminated, alumina-rich specularite; coarse specularite; coarse granular magnet ite. The first two are found only along the hanging wall, the others are found in all locations. The conglomeratic and "slaty" ores at the top of the formation are believed to have been concentrated by beach and/or stream winnowing during the erosion period which occurred before and during Goodrich time. After folding, faulting and dike intrusion which left the rocks in about their present positions, the chert bands, in the iron formation were locally leached, leaving the iron-rich bands to form ore bodies. In other areas the volume-for—volume replacements of chart bands by iron minerals was the ore-forming process. At the same time, or possibly later, much of the hematite in irregular areas of iron formation, ore bodies and Goodrich conglomerate was reduced to equigranular magnetite. The magnetite areas contain vuggy quartz veins carrying tourmaline, pyrite, chalcopyrite and very coarse specularite. The writer proposes that this chemical activity was accomplished by a fluid medium which entered the mine area from below along channels least, by structural features. This activity therefore took place after these structural features controlled in part, at had been developed. Since the platy hematite in such structually controlled ore bodies deformed around magnetite grains, the same period of deformation either continued during and follpwed mineralization or a later independent spasm of deformation occurred. is �7 INVESTIGATIONS IN TIU HECANBRIAN OF TI BIGHORN MOUNTAINS, WYOMING R. A. Hoppin, B. F. Hudson, K. A. Sargent State University of Iowa, Iowa City, Iowa In order to better understand the structural evolution of the Bighorn Mountains detailed structural, petrographic, and petrologic investigations, under the direction of the senior author, are being carried out in the Precambrian crystalline rocks. The investigations are directed toward the solution of three intimately related problems: ones to what extent do Precambrian structures control the local Laramide faulting evident along the margins of the range; two, is the regional trend of the range due to the presence of a major Precambrian structural feature or does the trend reflect the prevailing Laramide stress pattern; three, is the uplift due dominantly to vertical tectonics or to folding by horizontal compression. Initial field investigations have been completed along the marginal portion of the east—central part of the range. As a necessary complement to the detailed study of the crystalline rocks, the minor structural Preliminary results features of the adjacent sedimentary rocks were mapped. indicate; a local control of Laramide tear faults, in a NlO—15E direction, by strong Precambrian shearing; no apparent Precambrian structure controlling the trend of the range; an intimate relations of petrography and petrology to structure; and, a difference in the nature of deformation during the early Precambrian and the Laramide. The field work for two investigations, which have the same One is an objectives as the present studies, will begin this summer. east—west section across the range, beginning in the vicinity of the North Fork of Crazy Woman Creek then west approximately parallel to Highway 16. The second is a study of the Precambrian structures of the Horn, where a striking mineralogical layering occurs. To date six Master's theses, dealing with the complicated marginal sedimentary structures, have been completed. Four of these, together with the area of the University of Iowa field courses extend continuously from Little Goose Creek south to the Horn region. The remaining two deal with the northwestern portion of the range in the Five Springs area. A new project is to begin this sumner in the southwestern part of the range. projects now in progress include petrologic studies of a Precambrian rare earth deposit in the Horn region, arid of several small ultrabasic bodies, exposed along Highway 16 close to the eastern margin of the range. .Additional �8 NORTHERN CORDILLERAN CORDILLERPN REGION PRECAMBRIAN AGES IN IN THE NORTHERN PflECA14BRIAN AGES W, Gast Paul W, Pati]. of Minnesota, Minne3ota, Minneapolis, Minneapolis, Minnesota Minnesota University of The ages number of occurrences of The agesof of rooks rooks and and minerals minerals in in aa number of occurrences of Precambrian rocks Precambrian rooks in inWyoming, Wyoming, Montana Montana and and Utah Utah have have been been determined. determined. Detailed izwestigation mdi— Detailed izwestigation of of aa small small area areain in the the Beartooth Beartoothuplift uplift indi- Preliminary studies studies cates aa period period of of rock cates rook formation forniation2750 2750 m.y. m.y. ago. ago. Preliminary upliftssuggest suggest that that Creek—Bridger uplifts in the Wind Wind River, River,Bighorn Bighorn and and Owl Owl Creek—Bridger in the be represented there. be represented there. also also this event this eventmay may uplifts indicate indicate Other studies In in the Bowarid, and Wasatch uplifts Other studies the Medicine Medicine Bow Precambrian rocks in southPrecambrian rocks in southego. another rock rock forming formingevent event1600 1600 my. my. ago. another old m.y. old One occurrence 1350 m,y. occurrence of of 1350 eastern Montana are also also younger. eastern Montana are younger, One has been beenfot.uxd found inincentral Wyoming. rocks central Wyoming. rocks has �9 POSSIBLE USE USE OF PRECA1'il)RThN FRECA)RIAN CALCAROUS CALCAREOUS ALGAL ALGALCOLONIA COLONIA POSSIBLE AS INDICATORS OF POLAR SHIFTS Stephan C. Nordeng Technology,Houghton, Houghton,Michigan Nichigan Michigan College of Mining and and Technology, some i'eliminarvresults results of investigations This paper paper presents presents some preliminary This on calcareous calcareous algae algae recently recently undertaken undertaken at atthe theMichigan Michigan College of on Mining and Mining and Technology. Technology. kona Twenhofel, Collenia icons Twenhofel, 1918, is briefly redescribed. of the the literature literature onon calcareous calcareous algae algae and andofof numerous numerous Study of occurrences besides those those in in the occurrences besides the Kona Kona dolomite dolomite in inNorthern NorthernMichigan Michigan have have which by which conclusions concerning the mechanisms led led the writer writertotocertain certain conclusions concerning the mechanisms by mostimportant important of of these The most these the are controlled, controlled, The the colonial colonial growth growth forms forms are activity of be greatest greatest is believed sunlight. The believed to to be be sunlight. The activity ofthe thealgae algae would would be is on those portions portions of of the the colony colony receiving the greatest greatestamount amountof of sunlight sunlight on those and therefore colonial thedirection directionfrom from and therefore colonialgrowth growth should should be be aa maximum maximum ininthe the vertical vertical which the Thus, the amount sunlightisis received, received, Thus, the maximum maximum amount of of sunlight axes of of the the majority of colonies axes majority of colonies in in aa bioherm bioherni ot' o' biostrome biostronie should should point point toward the equator. equator. toward the Measurements made Colleniakona konaindicate indicate the equator was Measurements made onon Collenia This is essentially 27° North North 200 O West West in in Kona Kona time, time, This is essentiallyininagreenient agreement with with 27° measurements made Mountain—Loretto, Michigan, area measurements madeononalgae algaeininthe the Iron Iron Mountain—Loretto, Ivlichlgan, area bedsofofthe theseine same age. in age. in beds If the If thetheories theoriesofofmany many proniinent prominent workers workersininthe thefield field of of tectonophysics tectonophysics can can be be given given any any credence, credence, changes in position of the poles and equator equator have poles and have been beenfrequent, frequent, if if not not constant, constant,throughout throughout geologic geologic time. It time. Itis, is,therefore, therefore,very verylikely likely that that algae algaecolonies coloniesfrom from widely widely separated separated areas areas growing growing at at the thesame same time time may may have have different different axial axialincliinclinations but should be close agreement agreement asas totothe nations but should be in in close thelocation locationof of the the equator, thus furnishing furnishing a possible equator, thus possible means means ofofcorrelation. correlation. be be Time methods of Timepermitting, permitting, methods of study study disoused. discussed. and proposed proposedfuture futurework workwill will and �10 SUIvIMARY RADIOACTIVITY DATINGOF OFT}E T}E OFOF RADIOACTIVITY DATING SUIvIMARY PECM1BRIAN PECM4BRIAN MINNESOTA ROCKS OF OF I4INNESOTA ROCKS and A. A. 0. 0. Nier Nier S. Goldich Goldich end S. 5. University of of Minnesota, Minnesota, Minneapolis, Minnesota University Radioactivity dating supports aa three-fold Radioactivity dating three-fold division division of the aa two—fold than two—fold Precambrian rocks of the Lake Superior region rather Precambrian the Precambrian division as is is advocated advocated by Canadian geologists for division as for the three—fold division the three—fold division Canada; however, of Canada; however,aaconsiderable considerablerevision revision of of the suggested. used by the the Minnesota Geological Survey is suggested. used by Minnesota Geological Survey is by granitization granitization and a&1 Two major periods Two niajor periods of oforogeny, orogeny,accompanied accompanied by and 1.7 b y y approximately 2.6 2.6 bb yy and 1.7 b intrusionthat thathave havebeen been dated dated at granite intrusion at approximately Knife the Keewatin rocks and the Knife Keewatin rocks and division. the three-fold division. of are the basis of the three-fold are the basis Precambrian. Early Precambrian. Lake are assigned assigned to the Early Lakegroup, group,older older than than 2.6 2.6 bb y, y, are to the in Later Later The Animikie The Animikie group, group, formerly formerlyplaced placedwith with thethe Keweenawan Keweenawan group group in The (Medial) Precambrian. Precambrian, is assigned to the Middle (Medial) Precambrian. Precambrian, is assigned to the Middle Keweenawan group is isretained Late Precambrian. Precambrian. Keweenawan group retainedin in Late The makes the Precambrian, termiThe suggested suggestedclassification classification makes the Early Early Precambrian, termiArchean of the two-fold Archean of the two-fold nated by Algoman orogeny, nated by the the Algoman orogeny,equivalent equivalentto to the the inCanada; Canada; Middle Middle and and Late Late Precambrian Precanbrian are are classification commonly used in classification commonly used The The magnitude magnitude of of the the orogeny orogeny at at 1.7 1.7 b b y y equivalent the Proterozoic, Proterozoic, equivalent to to the uncertainty the uncertainty has appreciated in the past, pact, because because of has not not been beenfully fully appreciated in the of the of the granite intrusions. intrusions. of the age age of of many many granite b yy have have been been Metamorphism Metamorphism and end igneous igneous activity activityat at 1.3 1.3 — — 1.4 b elsewhere. dated region, and dated inWisoonsin, inWisoon3in, Michigan, Michigan, and and the the Sudbury Sudbury region, and elsewhere. of a y),although although apparently apparently not a Similarly not of Similarly the the Grenville Grenvilleorogeny orogeny (1.0 (1.0 b b y), mountain—buildingscale mountain—building scaleininthe theLake LakeSuperior Superiorregion, region, is is represented represented in in igneous activity. structural disturbances and in in igneous activity. disturbances and lesser structural solin solRadioactivity dating assistance in Radioactivity dating promises promisesto to be be of of great great assistance the problems of the Precambrian, although the limitations of analytiving the problems of the Precambrian, although the limitations of analytiving difficulties interpretation may may not cal and difficulties of of interpretation not be befully fully thethe cal procedures procedures and The The major major challenge, challenge, however, however, is is to to geologists, geologists, and and appreciated or appreciated or known. known. result only from the satisfactory solution of many of the problems will result only from the a satisfactory solution of many of the problems will a Fundamental geologic geologicinvestigainvestigaapplication of application of all allavailable availabletechniques. techniques. Fundamental tions, tions,including includingmapping, mapping, petrologic petrologic and and stratigraphic stratigraphicstudies, studies,are areneeded. needed. Results of radioactivitydating datingofofPrecambrian Precambrian rocks rock8 of ofMinnesota Minne8ota Results of radioactivity areas that that have have been beenpresented presentedatatpast pastmeetings meetingsofofthe theInstiInstiand adjacent areas Rb—Sr dating datingnow nowininprogress progress appears appearsto to support support tute are aresummarized. summarized, Rb—Sr tute useful termitermiearlier conclusionsdrawn drawnfrom fromK—A K-A dating. Development of a useful earlierconclusions problems. the Precambrianposes posesmany many problems. nology Precambrian nology for forthe �11 THOD TO OREEXPLORATION APPLICATION TOON ON ORE EXPLORATION GRAVITY METHOD APPLICATION OF THE GRAVITY W, J. Hinze J. Hinze Michigan State University, University, East Michigan State East Lansing, Lansing, Michigan Michigan The gravity The gravity method method has hasplayed playedananincreasingly increasinglyimportant importantrole role in the in the search search for for new new reserves reserves of of iron iron ore ore since since the thedevelopment developtnent of of This highly portable gravinieters gravimeters oapable capable of highly portable of aa high high degree degreeof of precision. precision. This method used in in the for methodhas hasbeen been used thesearch search forand andstudy studyofofdirect direct shipping shipping ores, ores, but has proven proven to be especially especially uaeful useful in in the the study study of of large large tonnage, tonnage, but itithas to be wide, near wide, near surface, surface, tttaconite "taconite typ& typett oreore bodies bodies which whichhave have been been the the priprimaryconcern mary concernofofthe the iron iron ore ore industry industry during during the thepast pastdecade. decade. The Thegravity gravity method methodwas was first first applied applied to to iron iron ore ore exploration exploration as as aa tool tool for fordetecting detectingnon—magnetic non—magneticores, ores, but but advantages advantages of this method over other exploration other exploration methods methods also also have havenade made it it useful useful under undercertain certain geologigeological conditions conditions in cal inthe thestudy studyof ofmagnetic magneticores ores and and regional structures favorable for for the the occurrence occurrence of iron iron ore. ore. However, the gravity method is restricted by which must restricted byseveral severallimitations limitations which mustbe berealized realizedand andunderstood understood In addition, addition, the the theapplication applicationofofthe themethod method is is to tobe be successful. successful. In ififthe full utilization methodisis dependenton onaacomplete complete understanding understanding Lu].]. utilization ofof thethe method dependent of the the density density relationships relationshipsofofores oresand an their contrast with the country count?y of contrast with the their rocks, rocks, This This is made particularly particularly difficult difficultby bythe thewide widerange range of densiis made ties of iron iron ores both positive positive and and ores which which can canlead leadto to the the association association of of both negative anomalies with ore bodies. bodies. The The result that the the negative gravity gravity anomalies with iron iron ore result is is that amount and quality quality of information information interpreted interpreted from the results results of of gravity gravity surveying surveyingisis aa direct function of the infornation the auxiliary auxiliary geological geological information available either either through throughgeological geological or or other other geophysical geophysical studies. studies. �12 GEOCHEMICAL SAMPLING OF LAKE BOTTOMS IN WINTER F. Read Read Williaxi F. William Lawrence College, College, Appleton, Appleton, Wisconsin Wisconsin In recent years, mining companies have carried out numerous stream sediments investigations of the heavy metal content content of of soils soils and and stream in an effort to locate concealed ore bodies. Little attention has been If mineralization is present beneath a lake, paid to lake sediments. heavy metals from this source may reach the lake bottom by groundwater circulation, or, under exceptional circumstances, by direct upward Anomalies produced in this manner should be distinct from diffusion. Anomalies anomalies due to inflowing streams, which are definitely concentrated around points of inflow. Winter sampling from an ice cover offers definite advantages deteriination of location, and (2) relative ease in in (1) precise determination handling of equipment. Severe cold can cause trouble, but this problem may be largely avoided by sampling either early or late in the winter equipment can can conveniently conveniently be be mounted mounted on on aa sma].l small season. The necessary equipment It includes (1) a power ice drill; (2) stainless fleet of toboggans. steel sampling sampling tube, tube, rope, rope, arid and winch; and and (5) (5) a supply of suitable A modified camp stove may be used to de-ice the sample containers. very cold cold weather. weather. sampling tube in very �13 AMINO ACID DISTRIBUTION IN LAKE DEPOSITS Frederick M. N. Swain Swain University of Minnesota, Minneapolis, Minnesota The bottom sediments of a wide variety variety of of lakes lakes were were studied Free amino acids are rare or absent in for their amino acid content. the lake sediments, but amino acids ranging from less than 2 ppm to more The than k000 4000 ppm were obtained in acid hydrolygates of the sediments. amino acids probably occur as glutelin or scieroprotein scleroprotein types of proteins, substances in in these these sediments. as peptides or tiere to humic acid acid substances Neutral peat peat deposits deposits and and well well humif humified led organic organic lake deposits deposits yield neutral and acidic amino acids in approximate proportions of 85:15; alkaline maria yield neutral and 85:15; alkaline bogs and well humified organic marls oniliamino acids in proportions of about 75:25; acid peats contain basic amino acids in addition to neutral and acidic types. Incompletely hwnified amino huniifiedlake lake deposits deposits yield yield variable variable proportions proportions of all three amino deposits proportions of of amino amino acids acids in in well well huniified humified deposits acids. The stable proportions are believed to be related to the zwitter ion properties of amino acids. Lake sediments of of low low organic organic content content generally generally yield yield small small There is little or no evidence of a amounts of neutral amino acids. relationship between type of lake sediment and individual amino acids. In deep, well huniified humified lake lake and and bog bog deposits, deposits, study study of of the the amino amino acids should help to reveal the depositional environment and history. �:Lli. FORNATION AND ORIGIN OF IRON IRON FORMATION ORIGIN OF THE CHEMISTRY CHEMISTRY MID THE Lepp Henry Lepp Henry University ofoflvlixmesota, University Minnesota, Duluth, Duluth,Minnesota Minnesota remarkUnaltered sedimentaryiron ironformations formationsofofall all ages are remarkUnaltered sedimentary ages are Calculations Calculations based based on on 200 200 analyses analyses of of iron content. in ably uniform in iron content. ably uniform of the theMesabi Mesabi scattered samplesofofiron iron formation forniation fron fron various various parts parts of scattered samples Fe. of from show thatthat 67%67 fall the range range of from 25 25 to to 32.5% 32.5% Fe. and Cuyu.ria ranges show fall in in the ranges and Cuyu.ria ironstone of England of the Liassic Cleveland ironstone of England Similarly analyses of the Liassic Cleveland Similarly of of136 136 analyses averagecompositions compositionsfor for other other Published average Fe. Published between 25-30% Fe. 85 between 25—30% contain 85%contain post—Cambrian type, post—Cambrian type, iron formations, or iron formations, be be they they Keewatin, Keewatin, Huronian Huronian or 30% Fe. Fe. almost irwariably show from 25 25 to 3O almost irwariebly show from normal iron iron Although appreciable leaner than than normal Although appreciablequantities quantities of of leaner billions of the the many my billions that of formationare areknown known to exist, is significant significant that formation to exist, it itis (or at formation there there are are no no (or at least least explorediron ironformation of of tons tons of of geologically geologically explored than 40% Fe, concentrations of more than 40% Fe, examples of mineable prims concentrations of more very few) examples of mineable prim very few) iron of iron important property property of an important This uniformity of of composition conposition is an This marked marked uniformity It suggests It suggests origin. may be a significant clue to their may and it sediments, sediments, main, the the result in the the main, pre—and andpost-Cambrian post-Cambrianiron ironformations formations are, are, in that thatpro— processes. the same same geologic geologic processes. of the be a significant clue to their origin. composition points to aacomplete complete The m6rkeduniformity uniformity of of composition points to The marked inconsistent with with It isisinconsistent sedimentary origin for for the sedimentary origin the iron ironsediments. sediments. It iron. hypotheses involvingdirect direct maginatio maginatic (exhalative) (exhalative) sources sourcesfor for the hypotheses involving the iron. of terms of of composition compositionininterms Attempts to explain explain the regularity regularity of Attempts to are unsatissilica aixi/or abundances of iron and silica are unsatissolubilities and/or abundances of iron and relative solubilities relative iron forforcarbonate iron they do do not not account accountfor for the moreover, they the carbonate factory, and, moreover, At At present present the the most mostlikely likely explanation explanationisis that that iron iron was was availavailable deposition asasFe(HCO3)2 andthat that the the resulting resulting able at at the the site siteofof deposition Fe(HCO3)2 and This should should sediments of CaCO3 sediments formed formed by by coprecipitation coprecipitation of CaC3and andFeCO. FeCO, This Diagenetic replacement of sediment with with about about 24% Fe. Diagenetio replacement of CaCO3 produce produce aa aedinient as would content as Si02would wouldslightly slightly upgrade wouldany ary precipiprecipiupgrade the iron content by by S102 tation tation of ofFe(lJO3)2 Fe(lJO3)2 as as oxide. oxide. mations, mations. �15 QUANTITATIVE ANDECONOMIC ECONOMICIMPLICATIONS IMPLICATIONS OF OF THE THE QUANTITATIVE THE PETROGiNETIC THE PETROGINETIC AND MINERALOGICAL VARIATIONWITHIN WITHINAALARGE LARGEGRANITIC GRANITICCOMPLEX COMPLEX MINERALOGICAL VARIATION E. H. Timothy lt)hitten \t)hitten Northwestern University, Evanston, Illinois A new and very very powerful analytical technique has been used to study the mineralogical variation within a large inhomogeneous granitic This quantitative modal study was made possible by detailed mass. sampling (two specLraens specimens per sampling (two per 1/1+ 11)4.square square mile) mile) of of an an entire entire complex and the In this paper the petrogenetic use of an an IBM IBM 650 6O electronic electronic computer. computer. significance of the mineralogical variation is emphasized, but the success with anai1ses anaises of potentialities in in obtained with of accessory accessory minerals minerals suggests potentialities economic prospecting. The methods are general and applicable to any area, but are to the the extremely extremely well-exposed well-exposed 'older 'older granite' granite' of illustrated by reference reerence to Donegal, been mapped mapped recently recently ]Jonegal, Eire, Eire, because because the the entire entire Donegal Donegal Granite has been The nature nature of of the the complex complex is is outlined outlined so so that that on the scale of 6"/mile. The the significance of the analytical work can be appreciated. The 'older granite', granite'9 the oldest component of the Donegal Granite, is a single single structural structural unit unit measuring measuring some some 24 2k miles miles from north north to south. In the southeast it is characterized by dioritic migmatites which contain innumerable metasedimentary rafts; these relics comprise Northwards and westwards the rafts well—defined ghost-stratigraphy. ghost—stratigraphy. a well-defined granite and the granite changes to aa typical typical two-feldspar two—feldspar granite are lacking and the granite changes to are lacking leucocratic granite (colour kO) leucocratic granite (colour and thence to highly quartzose (quartz ' kO) Contact relationships and flow patterns indicate that away index index << 1o). l). from the inigmatitic migmatitic area area homogenization homogenization was was accompanied by by magmatic magmatic flow flow and stoping. Concomitant with the gradual compositional change to unusual micro-textures micro—textures quartzose granite granite (taking (taking place place over over 5—10 —lO miles), quartzose miles), unusual increase, and and these these suggest suggest that that microcline microcline arid and quartz partially partially replaced replaced increase, these relationships relationships imply imply the the of these minerals crystallized previously. All of Firstly, chemical operation of two successive petrogenetic rhythms. processes created granodioritic magma at the expense of metasediments now represented by relics relics within within the the migmatitic migmatitic diorite; diorite; thi6 this essentially essentially Secondly, another homogeneous magma was intruded into adjacent areas. chemical metasomatic metasomatic phase phase generated generated more more quartzose quartzose granite granite at at the the expense of part of the virtually solidified granodiorite. Eventually such end-products became mobile and were intruded as minor transgressive plutons within within the the 'older 'older granite' granite' parent parent(see (seeWhitten Whittenl957a l97a —— Proc. plutons Nag. vol. vol. 9)+, 9k, Royal Irish Royal Irish Acad. Acad.vol. vol.58B, 8B, pp. pp. 2k5—92; 2L_92; l957b l97b —— Geol. Nag. 2—39). pp. 25—39). A Swift automatic electrical point counter enabled accurate modal analyses to be made rapidly. By the method of least squares linear, quadratic, and cubic cubic area]. areal trend trend surfaces surfaces have have been been computed computed for for each each Strong most accessory minerals within the 'older granite'. major and mo8t �16 and consistent gradients (trends) are apparent. The residuals (difference between the observed and computed surface values) for each phase clearly define palimpsestic ghost-stratigraphy. In some areas the pattern of the residuals can be directly related to metasedimentary rafts visible wi.thin the within the granitoid granitoid rocks. In other parts of the complex, the residuals constitute the only only detected detected relics relics of of the the metasediinents metasediments which which were were extant prior to emplacement of the 'granite'; that is, the residuals reveal previously unsuspected ghost-stratigraphy ghost—stratigraphy which is harmonious with the regional structure. This discovery is of considerable petrogenetic significance. �'7 17 EANINGOFOFTITh TI TRNS TMS GENIC MEA1'IING TI1 GENIC TUE REPLACEKN WDRGiHERivIAL A1D HEPLACEKN Ii'DRG]HERiL AIW G. Amstutz G. C. Ainstutz of Mines and Metallurgy, Rolla, Missouri Missouri School of Mines ard Metallurgy, ways different ways The term hydrothermal h1drothermal has been defined in many difCerent by the authors using it. the shools sool of which reflect the ofthought thought represented represented by which reflect of "hydrothermal" given A cross section through through many many different different definitions definitions shows that practically all during the last one hundred and fifty years shows hydrothermal solutions solutions or or fluids fluids to be hypogene; most of authors assume hydrothermal There is much disagreement confusion There is much disagreement or or confusion magmaticorigin. origin. assume magmatic them assume nature epigenetic nature of hydrothermal however withregard regardto tothe the syngenetic syngenetic or epigenetic however with and processes. processes. deposits and that the theterm termhydrothermal hydrothermal should should proposed that and proposed shown and It isishere hereshown It epigenetic orig1i. origi. Hydrothermal not be Given given aa priori priori aa connotation connotation of epigenetic hypoene physico..chemicalconcept conceptwhich whichalso also includes includes the the concept concept ofofhypogene is aaphysico—chemical notinvolve involveany anytime time concept. concept. Hydrothermal rocks, origin; doesnot origin;but butititdoes (autohydrothermal syngeneti (autohydrothermal be epienetic deposits, alterations, etc. may be epigenetic or syngeneti alterations, etc. may deposits, no proof proof se no Hydäthermal nature is thus per se Hydióthermal nature is thus per processes, exhalations, exhalations,etc.). etc.). processec, epigenetic origin. origin. for epienetic for be said said for for the the term term replacement. replacement. This term same can can be the same Much the wa often wai often loosely loosely used used as has been somewhat somewhat aa ma€ic magic word word in in the the past past aid and take take Epigenetic Epigenetic replacements replacements are are possible possible and and synonymfor forepigenesis. epigenesis. aa synonym syngenetic replacesyngenetic replaceThey require require however however many many more more assumptions assumptions than than place. They ment. Also, in many cases, an assumption of replacement is not justified, physicou.chemically since simple contemporaneous contemporaneoua crystallization offers a physicou'chemiCally Thus also with regard to sound explanation explanation of of origin. origin. and geometrically sound change in time may fall this term it must be said that a compositional classified be claesified as syngenetic. syngenetic. within the time of formation of a rock and has to be igneous e.g. autohydrothermal autohydrothermal changes chawes in in igneous Examples are abtmdant abundant e.g. rocks; doloriitization dolomitization or or other other changes changes in in sediments which often take place from geometric and and geochemical geochemicalcriteria criteria from Various geometric etc. Various during diaGenesis; etc. durin€ diagenesis; deposits, Valley deposits, the Superior copper copper deposits, deposits, from the Lake Lake Superior 'rom the the Mississippi Mississippi Valley the genetic genetic meaning meaning of of and fromother otherore oredepos deposits areuBed usedtotoillustrate illustrate the its are and from terus hydrothermal and replacement. the the terms �18 TILLITE OR TILLITE ORSUBAQUEOUS SUBAQUEOUS SLIDE? SLIDE? it. Dott, Jr. Jr. it. H.H. ]Jott, University of Wisconsin, Madison, Wisconsin Recent studies of turbidity current and associated slide deposits have opened new vistas to understanding many ancient sediments. sediments moving of sediments flow of Notably, the mechanisms of suspension and mass flow under influence of gravity provide provide means means of of transport transport of shallow marine or terrigenous clastics and organic remains to deeper water. Traditionsediments were ally, geologists geologists have have insisted insisted that that fl geosynclinal sediments deposited in shallow water because of abundant clastics. Furthermore, explained until until these these repetitious graded bedding was not satisfactorily explained Rhythmically-laminated sandstone, silstone mechanisms were evaluated. and mudstone associated with unsorted pebble and boulder beds have been rather universally interpreted as glacial varves and tillites respectively, geotectonics were were (arid (and and elaborate theories of ancient climatology and geotectonics are) erected upon this foundation. Concepts of turbidity current and slide deposition can best be such geosynclinal belts 8uch demonstrated in £n Mesozoic and Cenozoic strata of geosynclinal as the Pacific coast coast and and the the Alps. Alps. However, the interpretations can older fossiliferous older also be extended to certain more obscure and less fossiliferous (1957) reinterpreted reinterpreted Perinian Permian "tillites" "tillites' of northern northern Mexico, rocks. Newell (1957) Cretaceous and and Sanders Sanders (1957) (1957) challenged challenged glacial glacial interpretation interpretation for for boulder beds in Chile. Other examples were questioned long ago, but of the early dissenters dissenters were were little—heeded little—heeded in in the the "glacial "glacialenthusiasm" enthusias& of twentieth century. By analogy with well-documented turbidity and slide deposits of California and and Oregon, Oregon, it it is is reasoned reasoned that that the the famous famous Paleozoic tilliteu near Squantum "tillite" near Boston, Boston, Massachusetts Massachusetts possesses possesses so so many many similarities Submarine sliding of suspect. as to make the glacial interpretation suspect. rapidly deposited, deposited, volcanic—rich volcanic-rich sediments sediments is is proposed proposed as as an an alternate mechanisms of Absolute criteria for distinction of the two criteria for distinction of the two hypothesis. hypothesis. processes produce very poor Both produce very poor deposition are difficult to discover. sorting of fragment size and both can conceivably produce faceting and striation of pebbles. Only a preserved glacial pavement overlain by extensive, poorly—sorted till-like material (as in South Africa) seems unequivocal. General stratigraphic relations and tectonic setting serve In many geosyrigeosyrl— as as secondary secondary factors factors in in judging judging probability probability of of sliding sliding in Extending the reasoning, it appears that all ancient clinal clinal sequences. sequences. "tillites8 must be regarded with suspicion until critically re—analyzed "tillites" (as suggested by Crowell, 1957). Because of striking similarities of many Precambrian sediments and associated "tilhites" "tillites" to younger geosyn— order. clinal deposits, a re-evaluation re—evaluation of Precambrian glaciations seems in order. �19 GEOLOGYOF OF THE THE IRON IRON FORMATION FORMATION OCCURRENCE OCCURRENCE GEOLOGY ONTARIO NEARKAMINISTIKWIA, 1WiINITIKWIA, ONTARIO NEAR M. Ohlson Ohison John M. River, Michigan Michigan Iron River, Company, Iron Inland Steel Company, The iron formation near Kaministikwia, Ontario, outcrops Port within the valley of the Kaministikwia River, 18 miles northwest of Port Arthur, Ontario. Three vertically dipping strands of magnetite iron formation The rocks above and below the strike east-west to northeast-southwest. iron formation are volcanic flows, volcanic breccias, agglomerates, bedded and massive tuffs. The iron formation is highly magnetic and of red red stained stained chert, chert,hematitic hematiticmagnetite magnetite of beds beds1/Li." 1/LI." to to 3' 3' thick of consists consists of The iron formation white laminated laminated chert chert with with scattered scattered beds beds of of tuff. tuff. and white averages 600 feet in thickness. evidence to to determine determine the structural There is not not su.fficient sufficient evidence structural pattern in the Kaministikwia area at present. The three iron formations are either three stratigraphic units, one stratigraphic unit broken into segments by faulting, or two stratigraphic units, one of which is broken by faulting. faulting. into two two segraents segnents by The mineralogy of the iron formation together with the size of the quartz crystals in the recrystallized chert suggest that the iron formation is an original magnetite iron formation. �20 PLEISTOCENE POLLEN STUDIES IN MINNESOTA Fries and Magnus Fries H. E. E. Wright, Wright, Jr. Jr. and University of University ofMinnesota, Minnesota, Minneapolis, Minneapolis,Minnesota Minnesota of A program of study of the pollen content of the sediments of A selected Minnesota lakes and bogs has been initiated in the Geology Depart.. Depart.ment of the University of Minnesota with the aid of a grant from the Hill Family Foundation, for the purpose of working out the late-glacial and Sites have post-glacial vegetational and climatic history of the region. been selected with respect to the distribution of glacial drifts of different substages of the Wisconsin glacial stage and with respect to prairie). the present major vegetational provinces (conifers, hardwoods, prairie). Preliminary analyses for a buried peat layer near North Branch, Chisago County, suggest that the vegetation in this area during the Two Creeks interstadial interstadial interval interval about about 12,000 12,000 years years ago ago was was marked marked by by spruce spruce with many openings of grass, shrubs, and herbs. Analyses have also been made for a lake between drumlins about drwnlins were formed 30 miles north of Two Harbors in Lake County. The drumlins during the Cary subage of the Wisconsin glaciation, and the region was approached approached but but not not reached reached during during two two subsequent subsequent ice ice advances advances (Nankato (Nankato The first vegetation indicated after recession of the Cary and and Valders). ice was grass with perhaps both tundra and prairie plants and some spruce A pronounced but temporary influx of and willows on sheltered slopes. birch along with a reduction of spruce may record the warming of the Two Creeks (Mankato/Valders) interstadial, but the earlier Cary/Mankato interstadial is not recognizable in the pollen diagram. Subsequent changes involved increase increase of of pine pine to to aa maximum maximum about about halfway halfway through through the the post-glacial succession, along with a slight increase of oak, elm, and ash, suggesting a larger number of outliers of warmth-demanding deciduous trees than at present in this region. The latest horizons are marked by a decrease of hardwoods and a corresponding increase of spruce, fir and taniarack. tamarack. Glacial studies in the area indicate that the fluctuations of the Superior lobe and other ice lobes during the Cary, Mankato, and Valders subages of the Wisconsin glaciation probably exceeded 150 miles. Distinct climatic fluctuations are thereby implied, but the fact that only one of of the the two two possible possible interstadia]. interstadial intervals is suggested suggested in in the the implies either either that that the the pollen pollen studies studies are are not not yet yet suffisuffipollen diagraiu diagram implies ciently precise to to reveal reveal all all the the climatic climatic changes changes or or that that fluctuations fluctuations of the ice fronts were controlled not by gross climatic changes near the margin but by changes in conditions of snow accumulation or ice flow far back from the ice front. Continued studies will be directed particularly towards these problems of the late—glacial vegetational and climatic changes. �21 GEOLOGY AND AND GEOMORPHOLOGY RESEARCH IN IN GLACIAL GLACIALGEOLOGY CURRENT RESEARCH WISCONSIN* IN WEST—CENTRAL WEST-CENTRAL WISCONSIN* IN University Robert F. Black of Wisconsin, Madison, Wisconsin A program of research on glacial deposits of Wisconsin and their 1956. The modification by geomorphic geomorphic processes processes was was begun begun in in the the fall fall of of 1956. Research assistant program is carried on part time during the school year. L. A. Bayrock has completed one academic year and Elizabeth H. Kissling and and Thomas Thomas H. E. Berg Berg are are on on their their first first and and second second academic academic years years respectively. respectively. It is yet premature to draw definite conclusions from many aspects of the various studies so this abstract must cover essentially the nature of the program. Airphoto mapping of glacial deposits in Pepin, Pierce, St. Croix, Dunn, Polk, and Barron counties has yielded information on the distribution of various erosional and depositional features such as pro—glacial and marginal channels, pre-glacial drainage ways, outwash and inwash kmes, crevasse deposits, kames, crevasse fillings, fillings, eskers, eskers, kettles, kettles, terraces, terraces, bess, bess, moraines, and areas of thin drift. Field checking during the winter months has established the reliability and usefulness of this approach. Quantitative geomorphic studies of the development of the drainage network in representative parts of the area are underway. It is anticipated that they will wIll aid in correlation of the older drifts. Bottom sampling of kettle lakes and drained lakes has just been started. Youthfulness of Cary-age features in northern and western parts of the area readily readily distinguish distinguish them them from from subdued subdued forms forms of of Tazewell Tazewell and and The has been confirmed by Farindale has been confirmed by Farindale age to the south and east. Farrndale (W_7L47, U. S. Geological Survey) and (W—7'+7, 1000 carbonlLI. dates two carbon—114. dates of of 29,000 29,000 + (Y—572, (Y-572, Laniont Lamont Laboratory) Laboratory) years years B. 3. P. P. from from Hammond and 30,650 + 1640 southeast Pierce County County and and in in Pepin Pepin Deposits in in southeast Woodville respectively. respectively. Deposits and Buffalo counties have eluded positive correlation, but are also thought to be Farindale in age. Widely scattered pebble and heavy mineral counts, which have just been started, and depths of oxidation and leaching of drift have not been reliable measures of age or correlation. Much old weathered drift obviously is incorporated in young deposits. Modification of glacial deposits by gravity movements under climates that produced permafrost is Tazewell ice-wedge casts have diagnostic diagnostic of of Tazewell Tazewell arid and older older drifts. been identified identified in in aa kaiiie kame north northofofRichmond Richmondand andin inaa kame kame at at River River Falls. Falls. Thawing of buried Farmdale ice beneath younger deposits was not completed until after Gary Cary deglaciation. In addition addition to to furthering furthering our our knowledge knowledge of of the the Pleistocene, Pleistocene results of the study study will will aid aid in in determining determining buried buried bedrock bedrock from from indicator indicator erratics, in mapping of soils, in locating locating and and evaluating evaluating supplies supplies of of ground water and construction aggregates, and in analysing foundation problems. *Finced by *Financed by the the Wisconsin Wisconsin Alurni Alumni Research Research Foundation Foundation �22 THE LAKE ALBANEL ALBANEL IRON RANGE, GEOLOGY OF THE MISTASSINI TERRITORY, QUEBEC Terence T. T. Quirke, Quirke, Jr. Jr. Terence Forks, North Dakota University of North Dakota, Grand Forks, Territory is is The Lake Albanel iron district of the Mistassini Territory comprises between l50—l7 and comprises between 150—175 located about 11.00 miles north of Montreal and investigation; square miles. Since 1952 the area has been under intensive laboratory investigations geophysical, geologic, diamond drilling, and out. have been carried carried out. Precambrian age. rocks in in the the area area are are of of Precambrian consolidated rocks All consolidated of the Sam Gunner group to The oldest rocks are sediments and voleanics volcanics These sedimentary rocks have the north north of of the the Lake Lake A].banel Albanel iron range. range. the Takwa Mountains complex. been intruded by granites and gneisses of the complex are Mountains complex are Resting with angular unconformity upon the Takwa conformably overlain turn are conformably overlain the Papaskwasati. Papaskwasati group, rocks of the group, and and they they in turn are All these groups lie to the northwest of the by the Mistassini group. complex to to Grenville metaiiorphic metamorphic complex Mistassini (Grenville) fault zone. The Grenville basic intrusions, arid basic intrusions, the southeast of the fault consists of acidic and orthogneisses and paragneisses. formations. From oldest The Mistassini group consists of five formations. doloinites, Boulder Bay Albanel doloinites, to youngest these are the Lower and Upper Albanel quartzite, Teniiscamie iron—formation and and Kallio slate. The Temiscamie quartzite, Temiscamie iron—formation iron—formation has been been divided into six members. members. iron—formation have formed formed from from the iron-formation iron—formation are are thought thought to tohave Minerals of the The first minerals to and original silica gel rich in iron and carbonate. an an form were chert, siderite and in some cases hematite, magnetite and perinto the the early haps minnesotaite. Due to the incorporation of iron into minerals there was a subsequent enrichment of magnesium, manganese and calcium. These three crystallized into a dolomite structure. of the Chemical analyses analyses have have been been made made of of each each of of the the members members of These analyses are compared with similar Temiscainie iron-formation. iron—formations. Because of the general rocks of other Precambrian iron—formations. similarity of these iron-formations it seems probable that they were formed under similar circumstances. �23 NL!ERAL EXPLORJiTION EXPLORIiTIONIN INSOUTHERN SOUTHERNBJWFIN BFFIN ISLAND, MUIEBAL NW.T. James N, M, Neilson Neilson James Technology, Houghton, Michigan and Technology, Houghton, Michigan Michigan MichiganCollege Collegeofof Iining Iining end The paper The paperpresents presentsananaccount accountofofthe theregional regional geology geologyof of the the features physiographic The main physiographic features The main southernmost partofofBaffin Baffin Island. Island. southernmost part from the from the Kingaite Kingaite Peninsula Peninsula to tothe theFoxe FoxePeninsula Peninsula are are described described and and related in the of mineral related to to the therock rocktypes typesexamined examined in the course course of mineral exploraexploralithology and Precambrian The lithology and stratigraphy stratigraphyofofthe the Precambrian and and Paleozoic Paleozoic tion, tion, The are considered considered in in general general terms, terms, and and the the age age of of certain certain rocks rocks is is rocks are The effects The effects of of glacial glacial onthe thebasis basisofofradioactivity radioactivity dating, discussed on dating, discussed erosion are erosion are described describedtogether togetherwith withthe theeffects effects of of deglaciation deglaciatioriwhich which The resulted in infeatures featuresindicative indicative of both submergencearid andemergence. emergence. resulted of both submergence geomorphic processes thisregion region produce conspicuousexamples examples geomorphic processesactive active in in this produce conspicuous of and lacustrine phenomena, of frost frostaction actionand andsurface surfaceweathering, weathering, fluvial fluvial and lacustrine phenomena, mass wasting, illustrated, mass wasting,patterned patternedground, ground,etc.; etc.;these theseare aredescribed describedand and illustrated. Mineral exploration Mineral exploration procedures proceduressuitable suitabletotothis this pert part of of Baffin Baffin Island Island are discussed diacuøsed with reference to photogeologic interpretation, are withparticular particular reference to photogeologic interpretation, techniques,climatic climaticconditions, conditions,transportation transportationfacilities, facilities, prospecting techniques, prospecting It is is conconother matters mattersthat that affect affect operations. communications, and and other operations. conimunication, cluded that exploration in in this thisArctic Arctic regionpossesses possesses certain cluded that miners], mineral exploration region certain definiteadvantages definite advantages and and also alsosome some obvious obvious disadvantages. disadvantages. It �24 2k ENGLAND STRATIGRAPHY STRATIGRAPHY PROBLEMS IN PROBLEMS IN NORTHERN NORTHERNNEJ NEJENGLAND John C. C. Green Green John University of Minnesota, Duluth, Minnesota University Minnesota metamorphosed The "New Hampshire Hampshire and and Vermont Vermont sequences's sequences" of metamorphosed Paleozoic geosynclinal rocks are separated by a oontact contact of uncertain Because very few geologists have significance called the Monroe fault. worked in both sequences, correlation of the two has been a problem. This problem problem was was increased increased by by the the establishment establishmentin inl94.2 19k2 of of the the Orfordville Orfordville formation beneath the Albee formation, hitherto the lowest in the standard New Hampshire sequence of Billings (1937): many geologists believe that the Orfordville is the equivalent of several formations higher in the New Hampshire sequence. This interpretation is supported by the recent discovery by the writer in northern New Hampshire of a different group of rocks (Aziscohos formation) in the supposed position of the Orfordville. Aziscohos is stratigraphically beneath the Albee, as determined by The Azisoohos graded bedding in in several several localities; localities; the the position position of of the the Orfordville Orfordville was was determined by plunges of minor folds alone. fornation is thus removed from the column, If the Orfordville formation correlation between the two sequences is made much easier, and such a The establishcorrelation is now accepted by many New England geologists. ment of the Aziscohos formation beneath the Albee agrees better with this correlation, since the Aziscohos resembles the formations of the Vermont sequence immediately below the Moretown, which is correlated with the Albee of New Hampshire. �2 MAP AREA. WRIGHT MAP OFTHE THE MT. 4RIGH DEPOSTTSOF MID IRON TIlE GEOLOGY PdD IRON DEPOSITS TIlE GEOLOGY CANADA NEWFOUNDLAND, NEWFOtJNDLAID, Q,UEBEC QUEBEC S. S. Duffell Geological Survey Survey of of Canada, Canada, Ottawa Ottawa ,, Geological Ontario The Mt. Wright map area has been prominent in recent years because of the active active exploration exploration by by major major iron iron and steel companies of the large deposits of concentratable iron ore that lie within its boundaries. The iron iron formation formation includes includes aa nuuiber number of of facies of which the most important granular quartz, specular hematite and isto of is an oxide oxide facies facies that that cons consists rich and quartz rich bands bands nagnetite. magnetite. It is noticeably banded with iron rich and resembles the itabirite formation of Brazil. Friability and coarseness assets in in the the separation separation and and concen-' concen* of grain of the material are important assets tration processes required for marketing. The area covers part of the southwestern extension of the Labrador Trough and lies in the Grenville subprovince of the Canadian Shield but close to the Grenville Grenville Front. Front. equivalents gneisses that represent metamorphic equivalentB Rocks involved are gneisses miles to the north are relatively of units of the Labrador Trough that 50 gneisse8 may be divided roughly into three bands uninetamorphosed. unmetamorphosed. The gneisses that transverse the area in a southwesterly direction. The central and amphibolite facies facie of of metamorphism. metamorphism. southern bands may both be included in the amphibolite associated only with rocks of the is They differ differ in in that that the the iron iron foriiation formation is central band. gneisses, hornblende-' hornblendeThe southern band consists of graphitic gneisses, structurally garnet gneisaes gneisses and and their their migmatitic mimatitic equivalents. These structurally biotite garnet stratigraphica]ly overlie overlie overlie the iron formation and are believed to also stratigraphically central band of acid a synclinal structure between the occur in in a synclinal structure betweexi They occur it, it. souththe southsimilar rocks rocks in in the intermediate biotite—hornblende biotite-hornblende gneieses gneisses and and similar to intermediate iS formation is The neises with which the iron corner of the area. The gneisses with which the iron west corner sct5 about two two sot5 associated form broad anticlinal structures in which folding about associated taken place. place. has taken of axes has rocks of of the granulite €ranulite of rocks northern band band of of gneisses neisses i$ The northern is composed composed of mineralogy and physical facies of metamorphism that strongly resemble in characteristics the charnockite rocks of Precambrian terrains of other continents. The lower grade amphibolite facies of metamorphism appears to and is is interpreted interpreted facies and have been emplaced emplaced on on the the higher higher Grade grade granulite granulite facies being younger. as being younger. as Gravity Gravity surveys in the area by the Dominion Observatory proved extending across across the the existenceof ofa a phenomenally low low gravity anomaly extending the existence phexiomenally gravity anomaly of the transition zone between south of the transition zone between area direction just just south area in in aa southwesterly southwesterly direction being This gravity as being gravity low lowIs is interpreted interpreted as the two the two facies faciesofofmetamorphism. metamorphism. This the surface. below due to granitic batholith batholith not not far far due to the the presence presenceof' of aa granitic �26 T} CRETACEOUSSYSTEM SYSTEMOF OFMINNESOTA MINNESOTA THECRETACEOUS Robert E. Sloan Sloen Minnesota University of Minnesota, Minneapolis, Minnesota Cretaceoua rocks in Minnesota are Cenomanian to Coniacian age and andare arereferred referredto tothe theColeraine Coleraineformation formation in in age northern Minnesota and the Windrow formation in southern Minnesota. An Early Cretaceous and subtropical to warm temperate humid subtropical interval of deep deep weathering weathering under under humid regoliths on on the the underlying mderlying rocks climate produced a variety of regoliths rocks of two Paleotopographic, paleogeologic, and two Precambrian to Devonian age. Paleotopographic, paleogeographicmaps maps are are presented. The Cretaceous sediments are paleogeographic predominantly sandstones and shales with a few beds of lignite. They epicontinental sea were deposited on the eastern edge of the western epioontinental and include fluviatile, lacustrine, estuarine, estuarine, and and marine marine shelf shelf facies. fades. Out crops are scattered and exposures are poor. �27 STRUCTUB_LSTUDIES STUDIESIN INTTTHOMSON THOMSON STRUCTUBL FORHPTION, CARLTON COUNTY, MINNESOTA A, Mattson Louis A. Louis Univeristy of Univeristy of Minnesota, Minnesota, Minneapolis, Minneapolis, Minnesota Minnesota The Thomson formation formation is is aa thick thick series series of of slates and The Thomson graywackes that apparently accumulated in a relatively deep, quiet basin into which turbidity currents periodically flowed. Subsequently oxposed intermittently the series has been strongly folded and is now exposed belt trending southmiles in a belt trending square miles area of of roughly roughly 500 500 square over an area and Geologic evidence end radioactivity ages indicate from Duluth. westward from westward majordeformation deformationand andmetamorphism metamorphism are that the are pre—Keweenawan. pre-Keweenawan. themajor that Although thestructural structuralrelations relations of of individual individualexposures exposures can Although the formationhas hasremained reniained canbe bedetermined, determined,the theregional regionalstructure structureofofthe theformation can this detailed study During this keybeds, beds, During obscure forwent want of distinctive distinctivekey obscure for miles around arou.ndthe thetown townof ofCanton Carlton aa19 19foot foot of about about 35 square square miles an area area of of an "marker"member member was discoveredand andallowed allowedthe thedetermination determination of of the discovered "marker" was north—south cross—seccross-seclarger structural pattern in this this area. area. A 33 mile north—south reveals 33 large large synclines and 2 antiolines anticlines with many minor minor folds folds tion reveals estimates in in excess excess of of on their limbs. Although earlier thickness estimates 20,000 feet may prove correct for the entire outcrop area of the Thomson of exposed exposed beds in this this restricted restricted area area is is formation, the thickness of formation, approximately 3,000 feet. The Thomson Thouson formation has been intruded by a parallel swarm The numerotis anorthosite One of these dikes contains numerous of "diabase't dikes. dikes. These inclusions range in diameter end anorthositio gabbro inclusions. anorthositic from a few inches to 3 feet and are are believed believed to to be be related related to to the the Duluth Duluth If so, they represent the southwesternmost known occursouthwesterninost gabbro complex. rence of such rocks. Throughoutthe thearea areaevidence evidenceofofgentle gentlepost-folding post-folding deformation deformation Throughout planes have have been beenslightly slightly opened in places, exposed. Cleavage planes is well wellexposed. faults show show near vertical the "NE" joint et enlarged, tlatett faults "NE" joint sethas hasbeen been enlarged, the swarm has has been been emplaced emplaced parallel displacement, the dike dike swarm parallel to and and the displacement, ari1 probably occupying occupyingthe thewidened widened joint joint set.set. These features are probably probably related to the subsidence subsidence of of the the Lake Lake Superior Superiorsync].ine, syncline. � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1959 Description An account of the resource Proceedings of the Institute on Lake Superior Geology. University of Minnesota, Minneapolis, Minnesota. April 13-14, 1959. Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1959 Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/b32f9a4e4e14e52651577cfc480442d0.pdf d8ffa2bf8935b7f21a4e08a8d36c6ab2 PDF Text Text �TABLE OF CONTENTS Page 1. Building Index Map 1 Program 3 List of Speakers 9) Geophysical Investigation in the Wausau Area, Allinghatn, Robert G. Bates 22 Petrogeny of the Granophyre and intermediate Rock in the Duluth Gabbro of Northern Cook County, Ninnesota....RussellC. Babcock 8 Subsurface Geologic Structure in the Jacobsviile-Gay Area of the Kewesnaw Peninsula as Interpreted fron Geophysical Data....... .. 0. Bacon ,....... .... .,.,.. ... . .Lloyal 27 Magnetic Anomalies and Magnetization Qf Main Mesabi Iron Formation.....,...,.,,,......Gordon D. Bath, George M. Schwartz 15 A 14 Differentiation of the St. Croix and Emerald Moraines in West- Photogeological Study of a part of the Huron Mountain Area of Michigan..... ............,......,..........,...RLcttard C. Beard central Wisconsin.,... . ........... .. ... ... .. .. . . .Thornas E. Berg 13 Pleistocene History of Wisconsin...,..,,,.,..,,,.,Robert F. Black 12 Blac1 Shale Flyach Fades of the Ouachita Mountains, South.eastern Oklahoma..................., ......Lewis M. Cline 23 The Sangu Garbonatite, Karema Depression, S. W. Tanganyika, .Gerrard L. Coetee East Africa.. ,. 19 Geology of Northern Part of Florence, Wisconsin, Area, , . . . . . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . .Car]. E. Dutton 6 p... . ... .•.... .... . .. ... . ... Structure of th. East Gogebic Iron Range............T. E. Hendrix of 31 Increasing the Resolving Power Observations. 33 Iron Deposits in Cabon, Equatorial Africa.........Gilbert L. Hole 28 Magtetizations of Iron-formations and Igneous Rocks of Northern Minnesota..,.. ....... ... .. .. .Charles E. Jahren 20 A Change in Sedimentary Facies in the Little Commonwealth Area, Florence County, Wisconsin...,. .,...,...,Robert W. Johnson, Jr. Gravity and Magnetic �TABLE OF CONTENTS (Cant inued) Page 16 Quantitative Geomorphic Analysis of Stream Patterns in Westcentral Wiscornsin.,.................,..,..Elizabethfl. Kissling 26 Geology of the Soudan Mine, Northeastern Minnesota. . 21 ,. . . . . . .... . a,. . •, . . .• . • $ . . . . . . .F. L. 11 inger A Leptochiorite (7) from the Florence, gisconain, Area.. ...... ••••••••• •.................... ....Gene L. LaBerge 24 Pyroxene Paragenesis in a Mafic-Ultramafic ?lutoni. Complex., C. Luth 11 A Regional Gravity Study of Crustal Structure in Wiscon8 in, .,. .. . . . .• . ,. a .,• • *. •. .. . . . . . . . . . .John W. Mack 30 The Stratigraphy' and Structure of the NeCaslin Quartzite Region of Northeastern W'isconsin.....................Joseph J. }lancuso 10 Structure of the Earth's Crust in Wisconsin from Epleeion Seismic Obeervations........................... .a.,e*...,Robert P. Meyer, 3. S. Steinhart, George P. Woollard 5 29 Recent Studies of the Gunf lint Range, Ontario..Willard H. Parsons The Occurrence of carbonates Other Than' Superior iron. at iepth in. Lake IronFormatjoris,......,.............,,... . J..Rbyce 23 AilanIte Ocoorrencein the Horn Area,'BigbornMoüntaini, Wyomiitg. ..•. .• . . . . . . . . . . .., .. . . . ,. . .K. A. Sage'nt a,. . a,. a, a, 18 Lithofacies and Biofacies Variation in the Platteville .. Pormat ion of Southeastern Minnesota.. . . .,...... .Robert E. Sloan 32 Geologic Interpretation of Airborne Magnetometer Profiles Across Lake Superior1...1..0. . ••.. ....... . Edward Thiel 17 How Many Grains Should One Eount in Petrofabric Studies? . . a • • • • • . . • a . . • • . . . . . . . . . . . . . . . . . . . . . .James Trow ,,. . 7 Geological Investigation Southeast of the Palmer Area, Marquette District. a a *a a a •• a a a a e 0, a a a a .•a a. . . . . . .Just in Z inn �i a a 5 4 6 7 9 0 10 NAME NO. 36. &yoll6oo.o' 2. 64.461*0.1444* (*0,4 640*4) (4.43 37. 44*.s 5,,0. 3. 6g.Iool*ool 9.1164 144g. 4. 69.64413.144 (.96.6499 Eldg. 0.3 3$. 449Nooy Lo6,4.lol.) 9.2 39, iEoo, 3,14. llg$ 40. I14.4o.k.l 46*.. 1.o9) 6. Ag.k44loo*4 41.44 06 & 49.0*4*7 3..d *)dg. Ca 7. 676*04 fr.*oo4. (*6. 11.3 $ A.6l.*i. *0101490 *44g. 14.3 9. 4466*46 114.4 014k. 9.2 99. E.64 4444 1.4 (1. k*N6*l.qy 04 i2. Io.....d 44*9 93. 1*0*0* IloIl 14. k.l Cool. 0*... 44.9 IS Iinh..60q 144 14. *4.9. 14.41 97. I,ol.Co.o 54411494*ooo 9.6 £4 94 0.9 0.13 )t$.oJl.yMo.4)o,9 1.7 49. Co.i)Io.. 110.001 9.9 30. Chodboos..* 44*6 21. 05.14.97194 9.99 12 11 16.... 4og..ook. IL bns*.. I•fl. 042 66. No.4.. 14*.,..k 64 N.oooy kh6 9.3 70 44....' Dooty 0.2. 74. Oko.,..t.46 449 046*. .0.11 36) 41. 1lo.. #4*..*g..bo.l 'Moo,. 94 42. 410*90 9*4.1 0.3 43. Mg 014g. a I¼*.idg 46,.... L'Pooo.40 toWn 4* ltydo.o66. 4th. 14*19) 6 .lIygd.. '4*4* 16.14) 9.3 1141 4*11. 72. O.th,Ø$€ I4.p4I 73. PIo*og*.pl9o lob. Po.4940 boo.o0.thb.'IL O*1*$ .oo.I, la. **b 33) 14 P109044*99 *1d 3.oodtp 046*. 96 03 46. k.ib.oop 49. L.wo. *0144*04 0.*n9o.y 04 77. SoSop, KM 70. $1.6. Bldg 79. 3*6*. M,....64 4*46.1*4 00. 610.1 Cool,. 00.0466, 09. 5i..16o4..d 94. 9*04 i9 02. 54614*94909 34. 0,4041.44 95 1*40 444$3 22. 94041$1g* 00.19.07)444914 94 5.9*. Enogy 00,4*465.6. 0.7 94 33. 06.. )o6.oo4.*p 14*9.) 0.9 0.3 32. too $449 36. 4L..y 5.11*44644 $9. 64.440 44,0 24. 0,6,. 9... 23. 0.19 Cool. 001*0144 C..'.. 24. 94.o,boo 144 37. 94.ob..k *1,01. 94*0 C3 67. M.44. 110.00.4*4 4*6. 69 5o'doo' Ob,,o.so 1.46 39. 19,40.6.4 B0g6oy6q4ldg. 90 51i*1g. .4.l174*4.44144 03 39. MnoM& 9L,o.i 20. 099k.o.Sg Bldg.. (91,4.6,). 04 9134.4... too. 60. 9¼o*4*) 5o4.* 39. Eo.y,.o 1*441,1. 34 60*. 94*1* 9*4*0*0 0io6g 44*44 0.3 9$, 69*4) *0*69*4 39'W 94044 94. 466900.19 96p9.I, 02 144*.. 49*44 96. 9.. 44. 44.44 65140166,90* 94 Vo..,boo 16*6... 444 64. 14*6.44,4 9.7 31. 4o*o6o,. Alooo 04 32.94014044*0 9.4 33. fo..o.y $ *1144)14. 9.i 34 94*0141, *4.46414 9.3 63, )4*o& 4w*..6 t*b. 07. 01*4.4.,, 04.4.04017 90. WI.. C.oow 9)4 C3 64 44,o.( 1090 Aoo,sy 9941.9. 494gI. Sdo*4 I10d P,,(9.y 4o...,,h Lob) 0 93. :(Jg4.41y 04.4 93. 906.Mg 4 NoolIogy Bldg. 30. (,o.4.g )ood 46o.o 9440*111449) 3S0.oo6.94*..0b4,4. C 76 *1. 9,11. 23. C.,oog.o. )5..6.l 5*444*.) Bldg. *4 MooBooko) B 72. P*..booA.g 0IIi '76 9*941, 44.6 940 47. 11.6644*4 oooo 41*4169* 311 2ooon0.. 0444 A NAME 940. 0.6 67. Nook 44*0 E F C THE CAMPUS OF THE H UNIVERSITY OF WISCONSIN • AT MADISON. WISCOMSIN 1 2 3 4 5 6 7 6 9 10 11 1: �UNIVERSITY OP WISCONSIN Department of Geology and WISCONSIN GEOLOGICAL AND NATURAL HISTORY SURVEY Madison 6, Wisconsin Institute on Lake 14, Thursday 8:00 - Super4rGeo1o 8:30 April 14 - 15, 1960 . Registration - Wisconsin Center Auditorium Gallery SESSION I** Auditorium, Wisconsin Center Co-Chairman: Lloyal Bacon, Josiah Royce 8:30 0:35 9:00 9:20 9:40 10:00 10:30 Call to order and welcome.,..,,..............Eugene N. Cierott Busneasmeettng..............................RalphW. Marsden RECENT S'UDIES OF THE GUNFLINt RANGE, Parsons . . . .Wil lard H ONTARIO. . • .. STRUCTURE OF THE EAST GOGEBIC IRON RANGE...,.Thomas E. Hendrix GEOLOGICAL INVESTIGATION SOUTHEAST OP THE PALMER AREA, MARQUETTE ... ... . .Justin Zinn .. ,. •.. . ,... • DISTRICT.,.........,.,......... Coffee Break, Snack Bar, Basent SUBS1SRFACE GEOLOGIC STRUCTURE IN THE JACOBSVILLE.-GAY AREA AS INTERPRETED FROM GEOPHYSICAL PENINSULA OF THE DATA. .. . .. . . . . , .. . . . • . .••.. . • .. • .. .. .. . ,. .LloyaI 0. Bacon GEOPHYSICAL INVESTIGATION IN THE WAUSAU AREA, W. Aflingbam, Robert 3. Bates STRUCTURE OF THE EARTH' S CRUST IN WISCONSIN FROM EXPLOSION KEWBENAW 10:50 11:10 11 30 11:50 WISCONSIN.............,..John ... SEISMIC OBSERVATIONS.... ••. . . . .... . .• .. •, , a . ,. •. , P. Meyer, J. S. Steinhart, George . Woollard A REGIONAL GRAVITY STUD? OF CRUSTAL STRUCTURE IN a.. • , • . . • •1 WISCONSIN. . a •i•.• a a a. • , .John W. Mack .....,.,.Robert Luncheon, Snack Bar, Wisconsin Center SESSION II Auditorium, Wisconsin Center Co—Chairman: William Rea4 S. A, Tyler 1:00 1:20 1:40 2:00 2:20 2:50 BLACK SHALE FLYSCU FAdES OF THE OUACHITA MOUNTAINS, SO1JTHEASTERNOKLAUO4A.............,...,....,,.Lew'jeM. Cline PLEISTOCENE HISTORY OF WISONSIN.,.,.,.,......Robert F. Black -DIFFENTIATION OF 1E ST. CROIX AND EMERALD MORAINES IN STCENTRAL WISCONSIN.....................,..Thornas E. Berg A PHOTOGEOLOGICAL STUDY OF A PART OF THE HURON HOUNTAIN AREAOFMIdRIGAN...,.,,.,....,,,.,..........Rjchardc, Beard Coffee Break, Snack Bar, Basement QUAN'flTATIVE GEOMORPHIC ANALYSIS OF STREAM PATTERNS IN WEST—CENTRAL WISCQNSIN.............,...Elizabeth Ki$sling L ** Five minutes for discussion are allowed after each paper throughout the program. �2 PROGRAM (Cont hued) 3:10 HOW MANY GRAINS SHOULD ONE COUNT IN PETROFABRIC 3:30 LITHOFACT.ES AND BiOFACIES VARIATION IN THE I'LATTEVILLE STUDIES?.. , 3:50 4:10 4:30 • ,• • •• •, ••• .•. • •••,.• ., . . . ..... . . . ... .James 'I'row FORMATION OF SOUTHEASTERN NINNESOTA........Robert E, Sloan GEOLOGY OF NORTHERN PART OF FLORENCE, WISCONSIN AREA ,.........................,..,...,......,Carl E. Dutton A CHANGE IN SEDIMENTARY FACIES IN THE LITTLE CC*4)NWEALTh AREA, FLORENCE CoUNTY, WISCONS IN. ....R-obert W. Johns on, Jr. A LEPTOCULORITE (?) FROM THE FLORENCE, WISCONSIN AREA. . •. . .. . . . . . . . . •.. .. . . .. . . . . .. .. .. . .. . . .Gene L. LaBerge Dinner, Main Dining Ball, Wisconsin Center Basement Speaker: R. J. Anderson, Batteile MdiiorUI Institute Topic: "Journey into Ignorance. A Review of the Findings of the International :opbySiøaI Year" . 6:30 Friday, April 15, 1960 SESSION III Auditorium, Co-Chairman: 8:00 8:20 8:40 Wisconsin Center George Schwartz, Jack Everett PETROGENY OF THE GRANOPRYRE AND INTERMEDIATE ROCK IN THE DULUTH GABBRO OF NORTHERN COOK COUNTY, MINNESOTA...,.......................Russe11 C. Babcock, Jr, THE SANOtJ CARBONATITE, KAREMA DEPRESSION, S .W. TANGANYIKA, ...,.•. ,.• ..... .Gerrard L, Coetzee EAST AFRICA.... .. .•, PYROXENE PARAGENESIS IN A MAFIC'-ULTRAMAFIC PLUTONIC C0MPLX, BIGRORN MOUNTAINS, WYOMING,.. . •..,... W. C. 9:00 ALLANITE OCCURRENCE IN THE HORN AREA, BIGHORN MOUNTAINS, WYOMING.....,...........,...,.. 9:20 9:50 Coffee Break, Snack Bar, Basement Lut h ..........,.....K. A. Sargent GEOLOGY OF THE SOUDAN MINE, MORTHEASTERN MINNESOTA. ....... •.•,...•••..••.,,,..... .... .F. L. Klinger 10:10 MA(ETIC ANOMALIES AND MAGNETIZATION OF MAIN MESABI IRON.. 10:30 MAGNETIZATIONS OF IRON-FORMATIONS AND IGNEOUS ROCKS OF NORTHERN MINNESOTA..,.....................CharlêsE. .Jabven TEE OCCURRENCE OF CARBONATES OTHER THAN IRON A'!? DEPTH IN LAKE SUPERIOR IRON PORNATIQNS.... .......... Royce THE STRATIGRAPHY AND STRUCTURE OF THE NCCASLIN QUARTZ ITE REGION OF NORTHEASTERN WISCONSIN. .... ... .. . Joseph J • Mancuso INCREASING THE RESOLVING POWER OF GRAVITY AND MAGNETIC OBSERVATiONS.,.. .. ....., ....,.... .... .... .. .WiIL1 jam J. Hinze GEOLOqIC INTERPRETATION OF AIRBORNE MAGNETOMETER PROFiLES ACROSS LAKE SUPERIOR.....,. "5...,, ..•.... .. . ,.Edward Tidel IRON DEPOSITS IN GABON, EQUA!IORIAL AFRIcA...,..Gilbert L. Hole FORMATION........... .. .. . . Gordon 1). Bath, George 10:50 11:10 11:30 11 50 12:10 N. Schwartz ........J. �3 SPEAKERS JOHN W, ALLINGHAM..,.........,.Geologist, U, S. Geological Survey, Wa*hington, D. C. RUSSELL C. BABCOGK,Jz.......,,.Geologist, Bear Creek Mining Company, Aurora, Minnesota LLOYAL 0. BACON....S.,..... ... ..Associate Professor, Michigan College of Mining and Technology, I4oughton, Michigan ROBERT G. BATES.............U...U, S. Geological Survey, Washington, D. C. GORDON D, BATHII,...... S. Geological Survey, Menlo Park, California IIQ4ARD C. BEARD...,,41...,..,..,Pickands blather and Company, Duluth, Minnesota THOMAS E, BEIIG.,,.,....,.,,.,.,Graduate Student Department of Geology, University of Wisconsin, Madison, Wisconsin ROBERT F, BLACK...... . .Professor, Department of Geology, University ....... ...U, .,...,,,. of Wisconsin, Madison, Wisconsin LEWIS M. CLTNE.,,,....,,,........Profesaor, Department of Geology, University of Wisconsin, Madison, Wisconsin GERRARD L. COETZEE.,,. ,.,,Oraduate Student, Department of Geology, University of Wisconsin, Madison, Wisconsin .,Regional Geologist, U. S. Geological Survey, CARL E. DUTTON.. Madison, Wisconsin .....Depart'nent of Geology, Indiana University, THOMAS E. HENDRIX.. Bloomington, Indiana ,,Asaistant Professor, Michigan State University, WILLIAM J, HINZE......, East Lansing, Michigan GILBERT L. HOLE....,............Geologist, Bethlehem Steel Company, Bethlehem, Pennsylvania UARLES E. JAHREN.......... Physicist, U. S. Geological Survey, Austin, Minnesota ROBERT W. JOHNSON, JR..,...,....Geologist U. S. Geological Survey, Knoxville, Tennessee ELIZABETH H, KISSLING..,,,.,,.,,Graduate Student, Department of Geology, University of Wisconsin, M&dison, Wisconsin FREDERICK L. KLINGER Oliver Iron Mining ivision, U. S. Steel CorporatIon, Virginia, Minnesota GENE L. LABERGE..,...,,...,....Graduat€ Student, Department of Geology, University of Wisconsin, Madison, Wisconsin WILLIAM C. LUTH..,,.,,.,....,,..Graduate Student, Department of Geology, State University of iowa, Iowa City, Iowa JOHNW.MACK...,,.,,...,,,.,.,.GraduateStudent, Department of Geology, University of Wisconsin, Madison, Wisconsin JOSEPH J. NANCUSO. , .. .Graduate Student, Department of Geology, blichian State University, East Lansing, Michigan ROBERT P. MEYER..... .Asaistant Professor, Department of Geoleg University of Wisconsin, Madison, Wiscons in WILLARD H. PARSONS.....4.......Professor and Chairman, Department of Geoioy, Wayne State University, Detroit, Michigan JOSIAH ROYCE...,,. ,Piclcands blather and Company, Duluth, Minnesota KENNETh A. Student, Department of Geology, State University of Iowa, Iowa City, Iowa .............. ......Qeologist, . ...... .. ..... ..,.,. �4 SPEAKERS (Continued) GEORGE M. SCHWARTZ.... . .. ... .,Director, Mtnne8ota Geological Survey, Minneapolis, Minnesota ROBERT E. SLOAN.....,,..........Assistant Professor, Department of Geology, University of Minnesota, Minneapolis, Minnesota JOHi S, STEflqHART..... ,Graduate Student, Department of Geology, University of Wisconsin, Madison, Wisconsin EDWARD C. THIEL......4... .,.....Project Associate, Department of Geology, University of Wisconsin, Madison, Wisconsin .......Professor, Department of Geology, Michigan JNES TROW........ State University, East Lansing, Michigan GEORGE P • WOOLLARD.. .Professor, Dep-artment of Geology, University ......,.. .,.,. of WisonsLn, Madison, Wisconsin USTIN ZINN...... ......., .. ... ..Professor, Department of Geology, Michigan State University, East Lansing, Michigan �5 RECENT STUDIES OF ThE GUNFLINT RANGE, ONTARIO Willard H. TaraonS Wayne State The Gunf lint University, Detroit, Michigan iron..formation is located in Ontario north of Lake Superior. The range trends southwestward froin near Port Arthur to the Minnesota boundary. Throughout most of its length the Gunf lint is largely a arbonate iron-formation, but the western third carries appreciable quantities of magntite and hematite. In this part of the range there are insdse tonnages of low grade taconite. A number of studies have been carried out in recent years as to the economic possibilities of this taconite. Much of the earlier exploration has been confined to the lower Gunf formation. The present investigation suggests that the upper lint carries a higher concentration of magnet ite, Magnetic tube tests of the upper 200 feet indicate that a concentrate carrying 58-60 per cent iroft can be obtained, although it is somewhat high in (12-14 per cent)1 lint inf silica �6 STRUCTURE OF THE EAST GOGEBZC IRON BANCE T. E. Hendrix Department of Geology, Indiana University, Bloomington, Indiana Sttuctural analysis of the major and minor structures within the Keewatin and Huron ian roke stows there have been two periods of pre Keweenawan deformation on the East Gogebic iron range. The older of the two de.ormations is post-Middle, prs..Upper Huronian in age. This deformation local in extent and epeirogenic in nature. Fault block subsidence following outpouring of the Presque Isle volcanics has is resulted in the shifting and tilting of successive blocks of Lower and Middle fluronian a5s an area 8 miles wide in the east half of T.47., R.44W., and the west half of T,47N., R.43W. The subsidence was greatest towards the center of volcanism, causing part of the offset now apparent along the Presque Isle fault. The second and more severe pre-Keweenawan deformation is pestIt is regional in extent and Upper Huronian, pre-Keweenawan in age. orogenic in nature. This deformation appears to have folded also the southern iron ranges of Michigan and Wisconsin. The axis of apparent greatest principal stress is oriented northwest-eutheast. The apparent intermediate principal stress axis ic oriented northeast-southwest. The apparent least printpal stress is essentially vertical. The East Gogebic iron range was tilted to the north in Keweenawan This tilting does not appear to have extended east of Lake Gogebic because the Keweenawan flowS of the southetn trap ranges are is necessary, therefore, to postulate a practically horizontal. "hinge" between the two areas. There is a suggestion, as yet unproven, that this hinge may be the southward extension of the Keweenawan thrust fault, displaced to the south by a late Keweenawan fault that now trends approximately north-south through the center of Lake Gogebic. time. It �7 GEOLOGICAL INVESTIGATION SOUT}IEAST OF TUE PAlMER AREA, MARQUETTE DiSiRI( Just in Zinn Michigan State University, East Lansing, MichLga Thesis research on selected map areas southeast of Palmer during the past three years has been completed by Robert A. Vehrs, Armen Sahakian, and Richard A. Long. These studies have added some informa. tion that bears on several problems in this area, such as the questionable presence of post4uronian granite, the nature of pre-Huronian rocks existing here, and the true nature of the Palmer gnetss, Most of the gnetss of thIs area is a contorted hornbende gneiss with a foliation trending mostly east-*at, Its composition suggests metamorphosed basalt or andesite and it beLieved to correlate with the pre-.Ruronian greenstones found along the north margin of the Marquette district. The greiss is intruded by granite apophyses of possibly two ages, but most of the gtanita is of the pink to gray porphyritic type suggestive of Lamey's "Republic granite". Thin section studies indicate that the gneiss and at least most of the granite was sheared after their development, with some accomparying metamorphic alteration characteristic of the greenachist facies. This would indicate that the hornblende gee isa and the graflite intruding it are of pre-Euronian age. is Associated with the gneiss and granite are small blocks of slate phyl. I ite near Palr and a ridge of quartz rock farther southeast. The quartz rock, which looks like a quartzite ridge in the field, is actually metanovaculite and can not be correlated with any of the Ruronian formations in the district. The phyllite is very similar to pre-Hurontan rocks north of the or an argillite that occurs in Marquette district. A pre-Huronian age for these rnetasedttnentary rocks is suggested. Both the metanovaculite and the phyllite were Intruded by granite. This investigation failed to find any rocks of undoubted Huron ian Since the intruding granite itself age in the gneiss area studied, shows shearing and crude foliations in many piacee along with the development of some chlorite and epidots, it appears that it was Involved in the pos-t-Huronian orogeny. Therefore this granite must be older than the Hurontan. bodias war discovered. No undisputed post-Huronian granite �8 SUBSURFACE GEOLOGIC STRUCTURE IN ThE JACOBSVILLE.GAY AREA OF ThE KEWEENAW PENINSULA AS INTERPRETED FRC GEOPUYSICAL DATA L. 0. Bacon Michigan College of Mining and Techn9logy, Houghton, Michigan Magnetic anomalies occur in the Gay.JacobeviU. area of the Keenaw Peninsula1 an area composed of a thick section of Eastern or Jacobsvilie sandstone. Geophysical data indicate that depth to source is apptoxfinately 8,000 feet, which may be considered as probable thickness of the Jacobsville sandstone. Calculations indicate that one could be caused b material having a magnetic susceptibility of about 3000 x l0 egs units which is in the range of some of the felsites and also of the baslc flows of. the Keenaw Pen insul a. Spatial relationships indicate that the soutte of the anomaly most likely a felsite whlth could then have been the southeastern source for the felsite conglomerate beds as postulated by.W.. S. White of the II, . Geological Survey. is �9 GEOPHYSICAL INVESTIGATION IN THE WAUSAU AREA1 WISCONSIN John W. Allingham and Robert G. Bates U. S. Geological Survey, Washington, 0. C. Contacts and regional structural relations bett*en major rock units tn the Wausau area of central Wisconsin are defined by airberne geophysical data. Interpretation of data from a survey made in June 1956 shows that magnetic and radioactivity pattert tap materially assist geologic mapping. The Precambrian rocks of the Wausau area consist of a complex of volcanic and sedimentary rocks metamcirphoaed to the greenachist and amphibol it. facies and intruded by granite and associate4 granopbyre, and by syenite, diorite, gabbro, and diabase. Bedrock is covered by residual soil, glacial debris, and bess, and the area is now a plain of low relief except for resistant hills of quartzite. Areas of granite, diorite, hornblende gabbro, and diabase can be delineated by distinctive aeromagnetic patterns that are directly related to the magnetite content of these rock units. Arcuate patterns of high-amplitude magnetic anomalies are associated with skarn -and intrusive diorite in the central area of red granite and in the adjoining complex of apt itic syenite. The skarn and diorite are closely associated with pendants of quartzite distribution of which indicates that they are remnants of a large. f 614. and chlorite schist, the Adjacent to the red granite the structural grain of diabase dikes, hornbLlende gabbro, and dior-ite is indicated by the northeasterly trend of associated magnetic anomalies. Across the central part of the area individual diabase dikes of easterly trend can be traced for as much In these dikes, which contain accessory titaniferous as 12 miles. spinel, the remaflent magnetization is reversed and is much greater than the induced magnetization, and a sharp continuous low is produced. Well-def med medium—api jtude anomal its on radioactivity profiles clearly outline the syanite. Radioactivity lows are associated with the quarteite of Rib Mountain as well as smaller nearby quartzite beds. Rivers and swaps complicate the correlation of radioactivity unkts with the geology, particularly in Weston township. The Wausau region can be divided on the basis of radioactivity and magnetic data into areas character ized by (a) high-amplitude radia2 activity features and low-amplitude magnetic features, (b) tediumamplitude radioactivity and magnetic features, and (c) low-amplitude radioactivity features and high-amplitude magnetic features. These areas correspond respectively to red granite, aplitic syenite, and diorite or gabbro. �10 STRUCTURE OF TUE EARTh'S CRUST LN WISCONSIN FROM EXPLOS ION SE3SMIC OBSE1VATIONS R. P. Meyer, J S. Steinhart, 0. P. Woollard University of Wisconsin, i4aison, Wisconsin A series of seismic observations of blasts have been made to determine crustal structure in Wisconsin. A reversed profile 300 km long extends from the Apostle Islands southeast to Wisconsin Rapids and an unrersed. prof Lie 230 km long extends from the tip of Keewenaw Peninsula southwest into Wisconsin. These results together with the earlier work by Schlichter and consideration of the gravity anomalies allow the structure and physical properties of the crust to be deduced. Velocities in the major portion of the Crust are in the range 6.2 to 6.5 km/sac, and formal solutions for the depth to 14 discontinuity yield average dspths of 36 to 38 km. �11 A REGIONAL GRAVITY STUDY CRUSTAL STRUCTURE IN WIScONSIN John W. Mack University of Wisconsin, Madison, WIsconsin A regions], gzafrity Study øf Wiscofisin was conducted the purpose of finding if gravity information would lead to a bttèr understanding of large-scale geologic features and of crustal strt'eture. The data was statistically analyzed using a method developed by R. A. Haubrich (University of Wisconsin) of least squares fitting a two dimensional power series to the actual data points. A seventh degree polynomial fit of the data was assumed to be the regional effect. The residual map was formed by subtracting the regional values from the o-riginal data. The results of the residual maps and profile lines indicate a of the low density (2.67) granitic or acid igneous layer in parts of the State. The gravity picture also indicated the Moho is deeper under the central portion of the State than it is near the edges. The Mid-Continent gravity high, which extends from Lake Superior thickening into central Kansas, may be explained by changes in mass distribut ion above the mantle. �12 BLACK SUALE FLYSCII FACIES OF ThE OUACHITA MOUNTAINS, SOUTELEA$ThRN OKI.AROMA Geology Department, L. H. Cline University of Wisconsin, Madison, Wis. The sedimentary features of the upper Mississippian and lower Pennsylvanian Stan leyJackfork—Johns ValleyAtoka strat igraphic sequence of the Ouachita Mountains of Oklahoma are comparable to the typical black..ehale flyach facies of the Eocane and Cretaceous of the Alps and Carpatbian Mountains ef Europe.. The conclusion is reached that a predominately deepwater biackshale and radiolarian-chert environment was periodically interrupted by turbidity ctrents which debouched 4uartzoae sands derived frorn a nearby shelf environment. The presence of convolute bedding, graded contacts of sandstones and overlying shales, abundant flow casts, flute casts, and groove casts on the under surfaces of the sandstas, the general lack of cross-bedding and ripple tnatks, and the scarcity of fossils except for planktonie and nektonic forms support this thesis. The most characteristic feature of the StanleyJackfork sequence is the repeated alternation of unfossiliferous dark: shales and gray sandstones. The boulder-bearing Johns Valley shale represents what Alpine geologists call wild fiyecb; most of its lime stone erratics are depositional rather than tectonic in origin. The charts and the graptolitic shales of the 1owé Paleozoic represent a period of very slow sedimentation in a deep and starved arcuate trough. The 22,000 feet of post-.Arkansas novaculite sediments represents a period of rapid sedimentation during active tectonism. The Johns Valley shale lies stratigraphically above the Jackfork group, and it contains late Mississippian marine invertebrates indigenous to the low•r part of the formation; thus, the entire Stanley.-Jackfork sequence is pre-Pennsylvanian. �13 PLEISTOCENE HISTORY OF WISCONSIN Robert F. Black University of Wisconsin, Madison, Wisconsin Reconnaissance in all cnnties in Wisconsin, local detailed studies, and radiocarbon dates on deposits of the Wisconsinan stage provide data that necessitate a review of the Pleistocene history of Wisconsin. It now seems relatively certain that no Pleistotene deposits at the surface or buried are elder than the Wisconsinan stage, with the possible exception of some gravels ass igned to the Windrow formation, According to workers outside Wisconsin, the Wisconsinan stage began between 50,00 and 70,000 years ago. The earliest dated advance in Wisconsin, about 30,000 years ago, was synchronous in the Lake Michigan and Superiqr lpbes, This advance is here designated the Rock ian after the Rock River which traverses much of the area of deposition in southern Wisconsin and in Illinois. Subsequent deglaciat ion during the Farmdalian substage, 22,000 to 28,000 years ago according to data from Illinois, was incomplete—-ice blocks remained in the deep valleys until after the readvances of the ice during Cary time in southern Wisconsin and during Valders time in northern Wisconsin. These ice blocks subsequently produced many of our large lakes such as Mendota, Green, and Geneva in the south and cear,Twin, and Pelican in the north. Unfortunately, the chronology in Wisconsin of the Farmdalian deglaciation and subsequent readvancea and retreats of the ice up to the Two Creekan substage 11,000 to 12,500 years ago has no svpport of rádioOarbon dates and is imperfectly known. Permafrost was present for a time according to casts of ice—wedge polygons and to well-.developed solifluction and other frost phenomena. Primitive time and possibly somewhat man was in the Stste during Two Creeks earlier. �14 DIFFEREL4TIATION OF THE ST. CROIX AND dERALD MORAINES IN WEST-CEL WISCONSIN Thomas E Berg University of Wisconsin, 4adison, Wisconsin Deposits of three distinct glacial advances of Wtsconathan age are present in westcentra1 Wisconsin. Because of their lithologic similarity, the three drifts are distinguishable most easily on a geomorphic basis. The youngest deposit, the St. Croix moraine, trends SW-NE across the area. The main moraine is characterized by l1 -developed knob-and-kettle topography, unconnected drainage, numerous inwash areas, and lakes. The limit of advance is distin guished by reworked outwash, outwash channels, and thin ice-stagnation features about 4 miles in front of the main moraine. In the northeaSt corner of St. Croix County outside the St. Croix moraine, slightly older drift, here named the Emerald moraine from deposits near Emerald, Wisconsin, is characterized by subdued topography) ntmierous boulder piles scattred over the surface, and poorly integrated drainage. Subdued kettles are present; some are filled and others have been drained. Kames are present on the uplands. The east boundary of the moraine is approximated by the drainage divide separating the WIllow Rivet from the Cedar River. The oldest drift is distinguished by well-integrated drainage, fossil frost benomena, absence of kettles, and a more strongly eroded topography, The basal till in the oldest drift has been radiocarbon dated at approximately 30,000 years before the present, or late Altonian. The Emerald moraine is, therefore, tenatively assigned an Early Woødfordian ae and the St. Croix moraine a Late Woodfordian age. �15 A PROTCICEOLOGICAL STUDY OF A PART OF tuE UURON MOUbTAIN ARE& OF MICRIGAN Pickands Richard C. Beard Mather & Company, Duluth, Minnesota A study was made of the uses and limitations of photo—geology in the mapping of an area of moderately thick glacial cover and relatively complex structure. A part of the Precambrian shielñ are.a ot Michigan was chosen for this study and the procedure employed was one that made full utilization of aerial photographs in all three phases of geological investigation: planning, field Use, and compilation. It was found that the regional structure is quite easily inter- preted from the aerial photos. It consists of several plunging folds, which were easily traced by a sharp escarptent betweet more resistant basement rocks and softer overlying flfles. Thin and discontinuous bands of other sedimentary rocks occur stratigraphically between the basement and the overlying slates. While not easily racognized in the photos, these bands were located by field checks concentrated along the escarpment. Some local folding in the slate area could also be traced thru the blanket of glacial material, without any visible outcrops. Topography and drainage reflects a prominent fracture pattern, especially in the areas underlain by basement; and where these fractures intersect cofttacts, the relative movement was often evident. Numerous basic dikes, although observed in the field, show little topographic expression and. are therefore not recognthable in the photos. �16 QUANTITAT!VE GONORPR1C MALY$IS OF STREAM PATTER1S IN WEST.-CENTRAL W1SCOZSIN Elizabeth H. Kissling University of Wisconsin, Ma4ison, Wisconsin In a quantitative study of first—order streams in westcentral Wisconsin the lengths of streams, basing, and divides, the areas of the basins, the angles at which the streams enter others, and the direction of stream flow were measured in eight areas. Drainage density was calculated and the shapes of the basins analyzed. The data and the calculated quantities were tested statistically to determine whether they were normally distributed, and the groups. were compared and tested for significant differences. Histograms and graphs representing the data allow no definite conclusions Plots of the probabilities that the data for each group were normally distributed suggest the presence of three types of streams. The tests for significant differences also show three different groups, but the members of these groups do not always coincide with the rnembers of the probability types. The results are theef ore inconclusive in attempting to differentiate various ages of tills jn this area. �17 ROW MANY GRAINS SHOULD ONE COUNT I PETROFABRIC STUt)IES? James Ttow Michigan State University, East Lansing, Michigan In an effort to determine the minimum number of grains that one. must count to achieve reliable results in a U—stage analysis of quartz student a measured çrientation of 2,300 quartz grains from one thin with a maximum concentration of 33% per 1% of the area of the hemisphre of projection. The students participating in the std were or ieatat the ion in the Sturgeon quartz ite, the fol lot ing crysa1ographic aecti DavA ings, Mihaal Gorycki, Martin 'Horowitz, David Huthson, Reger K irkpar icic, small grain Thomas Manley, Richard Thompson, an4 James Wallace. The observations were subdivided into 100-, 200-, and 300-grain amp1es for emparison to the distribution in th total 2,300- sample. A chi—square test fr goodness: of itt showed that from 120 to 180 grains must bs counted to attain the conventional 95% confidence limit of classical 8tatistics. �18 LITHOFACIES AND BIOFACIES VARIATION IN THE PLATTEVILLE FORMATION OF SOUTHEASTERN MINNESOTA Robert E. Sloan University of Minnesota, Minneapolis, Minnesota The variation in facies of the Middle Ordovician Platteville in southeastern Minnesota is related to the major structural features of the area, the south edge of the Twin City Basin and the Red WingRochester anticline, and shows that these structures were fgrmed during the deposition of the Platteville formation. Individual beds of limestone and shale partings are traceable for distances up to 100 miles, and a precise lithostratigraphic correlation network has been. established for the entire area. The principal source for the clastic component is the landmass Siouxia to the northwest. This landmass had a maximum possible width of about 250 miles. Bottom faunas were controlled principally by bottom sediment type, and observed faunal changes are the result of changes in sedimentation. The only fossils that occur in all lithofacles are the conodonts, which are most numerous in shallow water or shoal fades. The density of conodonts per gram of limee stone can be used as an important rock parameter and, when contoured, reflects the structural features of the basin. �19 GEOLOGY OF NORTHERN PART OF FLORENCE, WISCONSIN, AREA U'. Carl E. Dutton S. Geological Survey, Madison, Wisconsin The northern part of the Florence area contains strata of Middle Ptecambtian age. The rocks strike northwesterly, are steeply inclined, and are folded and faulted. The northernmost part of the area is underlain by iron—formation, slate, grayvacke, and greenstone that are the southeastward cont&nuation of part of the Paint River and Baraga groups of Iron County, Michigan. These strata are in a northwestward-plunging syncline, but most of the southwest Unib is missing because of truncation by a fault. Rocks in this syncli.ne are in chlorite grade of metorphism, but those elsewhere in the northern part of the area are in biotite or garnet grade. Another sequence is exposed- southwest of the fault, and a prominent unit is quartzite with excellent cross bedding that indicates top toward the southwest. Sericitic slate is older than the quartzite; slate, graywacke, and some silicate-magnetite ironformation are younger. A third sequence, farther southwestward, has two thin discontinous members of iron silicate-magnetite rock separated by gray slate that locally has graded bedding;' massive and ellipsoidal greenatone is also present. This sequence is in a northwestward-plunging anticline, is probably younger than the quartzite-slate sequence, and is apparently separated from it by a fault. Somewhat similar rocks that are probab1y repetition of the third sequence occur to the west in what is apparently a sotitheastwardp1unging anticline. Between the two anticlines repetition of part of the Paint River group occurs in a southward-plunging synci me that is cut ofE to the south by a fault. A few outcropS in the southwestern part of the area are sericitic slate and probably are repetition of part of the Michigamme slate of the Baraga group. �20 A CHANGE IN SEDIMENTARY FACIES IN TUE LITTLE C'Dt1WLTH AREA, FLORENCE COUNTY, WISCONSIN Robert W. Johnson, Jr, U. S. Geological Survey, Knoxville, Tennessee The Little Comflton**altb exploratIon area ie underlain by highly ferrugthous slate and graywaclce that are closely associated with and extend about 2,000 feet beyond the southeast end of a cross_bedded vitreous quartzite. The close association of these rQcks and the; numerous occurrences of breccia have been attributed to faulting or eros1nal unconformity. The8e conditions may exist locally but they are of minor significance; the character and distribution of the rocks at Little Commonwealth are primarily the asult of a change in sedirnentry fcies. equivalence of the ierruginous clastic rocks with the ttreous ajuartzite appears to be established by adjacent throughStratigraphic going older aericitic phyllite on the north and younger distinctive slate and graywecke on the south. Strata that underlie the villages of Foree and Commonwealth are the southeastern continuation o the Paint River group of Iron County, Michigan, and are in the northeast limb of a syncline. The ferruginous rocks and vitreous quartzite are located on of the southwest limb of the syncline, but continuation cs bedding refutes this possibility. in the Little Commonwealth area are not from the ferrugthous slate of the Paint relations suggest that the former are of upfault ad. the. apparent direction of The ferruginous elastic rocks distinguishable lithologically River group, but structural pre-Patnt River age 'and are �21 A LEPTOC}ILOITE(?) FROMThE FLORENCE, WISCONSIN, AREA University Gene: L. LaBerge of Wisconsin, Madison, Wisconsin An unusual iron-rich chlorite occurs in the Huronian rocks west of Florence, Wisconsin. The principal occurrence is stratigraphically just above the. quartzite at Keyes Lake. The mineral occurs locally as the almost exclusive constituent of a heavy, massive chlorite rock; however1 it generally occurs as metacrysts or veins in the conglomerate, graywack., and slate at the top of the quartzite. Its association with garnet, toirmaline, biotite, normal chlorite, magnetite, pyrtte, and stil.pnomelane also attest to its metamorphic origin. Chemical analys is and thin sect ion stud lea indicate that the mineral is different from other ch]orites in composition and optical properties. The total iron content is about the same as for thuringite, but the ferric iron content is much higher than it would be in a normal chlorite. The birefringence and p1echroism are much more pronôunced than in normal chiorites. In fact, the mineral could be mistaken in thin section for a pale green biotite. X-ray analysis, however, gives a powder photograph that is almost identical with a thuingite from the Soudan mine at Ely., Minnesota. �22 PETROGENY OF THE GRANOPHYRE AND INTERMEDIATE ROCK DULUTH GABRO OF NORTHERN COOK COUNTY, MINNESOTA IN Th Russell C. Babcock, Jr. Bear Creek Mining Company, Aurora, Minnesota The telationship between the granophyre and the gabbro within the northeastern projection of the Duluth gabbro complex was studied to determine the origin of both the granophyre and the associated tsjnternis_ MateH rocks. To best understand theme relationships between rock types the transition from gabbr to granophyre was investigated in detail. The variation in abundance of the common minerals was determined with point counter analyses, and the sequence of mineral formation was determined on the These were then related to both major and minor structtral features of the complex. basis of textural features. The presence of two distinct rock types, gabbro and granophyre, within the notheastern projection of the Duluth complex is thought to be a result of fractional crystallization and differentiation through gravity settling and structural activity. Upon emplacement of magma, the gabbroic minerals plagioclase and pyroxene crystallized, and, owing to their greater density, accumulated in the lower portions of the magma chamber .ihere they were knit together Ly continued crystallizatio1. The liquid which remained in the interstices reacted slightly with the crystalline phase and then solidified in the form of intergrown quartz and potassium feldspar. The resulting rock is a gabbro with minor amounts of interstitial granophyre. The essentially complete crystallization and accumulation of the abbroic constituerts caused the residual liquid to become more acidic in composition and to crystallize as a granophyre. The texture o the granophyre is the result of crystallization of intergrown quartz and potassi feldspar from the liquid surrounding scattered euhedral plagioclase crystals. The mafic minerals which are disseminated throughout this rock are fine, scattered altetation products of pyroxene crystals which formed earlier. The intermediate rock represents the gradational separation of gabbro and granophyre. Upward from granophyrs the gabbro the amount of interstitial and alteration of mafic minerals increases, farming a rock a diabasi texture as does the gabbro but which contains which has abundant thterstitial granophyre. As the granophyre becomes more abundant, the correspondin decrease ip gabbroic minerals causes the diabasic texture to disappear an• the rock appears as a mafic granophyre. Sttuctural activity has compl icated the expected distribut ion of rock types, causing amounts of granophyre to be concentrated bøth locally and regionally in excess of that which could have formed from fractional crystalliaation and gravity settling alone. �23 TIlE SANCU CARBONATITE, KAR4A DEPRESS ION SOUTHWESTERN TANGANYIKA, EAST AFRICPS University Gerrard L, Coetzee of Wisconsin, Madison, Wisconsin The basemmnt rocks of the Karema Depression consist of quartzofeispathic gneisses, amphibolites, metasediments and various intrusives that occur in a large synclinorium which plunges norttnest. Patches of post-basement sediments of several ages occut in the area. Two major subparallel faults in the Depression link the Rukwa Rift Valley on the southeast to the Great Tanganyika Rift to the west. Three lenses of carbonate rock, all aligned on the same northwesterly trend, occur over 16 miles of strike along the northernmost fault and on the south limb of the synclinorium. These are thS Sangu carbonate rocks, previously regarded as basement metasedimflts, but 5ho by detailed mapping to be discordant to the basement rocks which are locally tightly overfolded, The post-basement Ifume series se4jtnentary rocks are intruded by vein-dikes of the various catbonate rqck types. The carbonate rocks comprise white and red calcitic units and a dolomitic unit. These occur as narrow bands, lenses, and irregular masses that commonly trend oblique to the main body. Fine-.grained feldspatbic and siliceous rocks are closely associated with the carbonate rocks. "intrusive" contacts prove the siliceous and feldspathic rocks oldest, followed by the dolomitic, the white calcitic, and then the red calcitic rocks. Apatite and magnetite are ubiquitous in the carbonate rocks but phiogopite, tremolite, quartz, pyrite, and feldspar are common. Soda amphibole, barite, and serpentine occur in small amounts and accessories include zircon, baddeleyite, pyrochlore, rutile, titanite, chalcopyrite and fluor-apatite. Field relationships prove that the carbonate rocks are not basement liniestones. these rocks have a typical carbonatite mineralogy. The I ine-grained feispathic rocks closely resemble fenites, usually associated with carbonatites. The lack of associated undersaturated igneous rocks and the presence of fissure rather than the ring structure are unusual but not unique for carbonatites. �24 PYROXENE PARAGNESIS Th A 4AFIC-ULTR IC PLUTONIC COMPLEX, BI1ORN MOUNTAINS, ¶fONING State W. C. Luth University of Iowa, Iowa City, Iowa The complex that lies wIthin the Precambrian para—(?)gneiss core of the Bighrn untains is 9.5 miles west of Buffalo, Wyoming, on U. S. Highway 16. It has an elongate subelliptical outcrop pattern trending N.60°E. and enclosing an area of 1.2 square miles. The rock types of the complex may be categorized under the broad headings of peridotite, pyroxenite, norite, diorite, and amphibolite. Major constituents present in varied amounts include orthopyroxene (Of 1748' olivine (Fa1 2s' diopsidic augite, pigeonite, various aniphiboles (cummingoruta, act'inolite, anthophyll its, and hornblende), biotite, quartz, and plagioclase. Minor constitents include chromite, magnetite-ilmenite, pyrite, and apatite. Alteration products in the ultramafic rocks characteristically are antigorite, chrysolite, serpophite, talc, magnetite, hematite, calcite, tremolite and iddingaite. Of particular interest is the anamolous (Hess, 1941) presence of pigeonite in the coarsegrained ultramafic rocks. The intimate association of the three pyroxenes, diopsidic augite, pigeonite, and bronzite, causes very peculiar textures. Textural evidence suggests that diopsidiC augite formed in part prior to, and n part contemporaneously with pigeonite and bronzite. Pigeonitebrorizite relationships are exceedingly complex and appear to result primarily The, available from incomplete inversion of pigeonite to bronzite. physico-chemical data derived from the quaternary system MgOFeO— CaO-SiO also suggests the early and contemporaneous formation of diopsidc augite with respect to pigeonite, and later inversion of pigeonite to bronzite. �25 ALLANITE OCCURRENCE IN THE HORN AREA, BIGHORN I4OUNThINS, WYOMING K. A. Sargent State University of Iowa, Iowa City, Iowa The Horn area of the Bighorn Mountains is approximately 35 miles southwest of Buffalo, Wyoming. It is readily accessible by secondary roads from U. S. Highway 16. Quartzofeldspathic gneiss covers most of the 18 square miles of Horn and shows a distinct layering throughout the area. Feldspathic rock (albite-.biotite), amphibolite, and calcite marbles are less coamton. Shearing is common in the more competent rocks; contortion, flowage and lenstug are common in the oarbonate layers. Recent areal work suggests that these rooks are metasediments of the atauro1itequartz subfacies of the almandine amph.bo1tte facies. the Allanite is fairly common in gneisses throughout the Bighorn Mountains, in the Horn found in greatest aburt4ance along zones adjacent to the carbonate rock. These zones, ranging in width from zaro to about four area it is feet, also contatn diopside, tremoliteact inolite, epidote, and garnet, They resemble typical skarn however, no igneous rock is apparent. Tabular allanite grains range from submicroscopic to 3 cm in length, they carry 51O% Ce, 3—5% La and noteable ounts of Nd and Tb. Most grains show metamictization:; zoning is common. Some of the allanite is believed to have formed by replacement of epidote; however, the source of the rare-earth elements is unknown. Prospect pits and trenches dug in search of radioactive minerals common throughout the Horn area. Staking was done in 1954—55, along a zone parallel to and inc1uding the carbonate rock, mostly on the basis of geiger-counter investigation and the great abundance of vitreous black minerals. A radiometric survey made by the author in the area of greatest trenching revealed low readings, Further work showed the presence of thorium-bearing allanite, but the largest percentage of black minerals is andradite garnet. are �26 GEOLOGY OF TIlE SOUDAN MINE, NORTHEASTERN MINNESOTA F. L. Klinger Oliver Iron Mining Division, U. S. Steel Corporation, Virginia, Minnesota The Soudan mine is located in the waster part of the Vermilion In this area depoeits district, 2 miles north of tb. Mesabi range. of massivs hematite are found in steeply dipping rocks of Earlier Precambriafl age. The hematite deposits are associated with the Soudan iron—formation, whLch occurs as lenticular beds within the Ely green— stone. The ore deposits are found in a belt of greenstone and iron formation that is flanked on the north and south by sedimentary rocks correlated with the (Medial Precambrian) Knife Lake group. The rocks of the area strike EW to N. 80° E. and dip 75850 N. The greenstone is made up. of a complex group of chioritic and serleitic chists derived from flows, intrustves, fragmental rocks and sedentary rocks. Despite stron.g alteration and the development of schistsity, primary textures and structures are retained in the .greetons and indicate that these rocks are riot extensively sheared. ion from bas j.c to acidic, and the basic The rocks range in compos vartet-ies are notably deficient in lime; this contrasts with the basaltic compgition of greenstone from other parts of the Vermilion distr'iet. A zone of siliceous and sericitic rocks, resembling tuffaceous sediments, is found adjacent to the main belts of iron- it format ion. The iron—formation shows mappable changes in apar lithology, which in a regular order as ehert, lean jasper, and jaspilite. he distribution of lithologies is interpreted as vertical and lateral facies changes. A stratigraphic sequence is proposed, consisting of basal chart uc.ceeded upwards by lean jasper and jaspilite. The main bodies of iron-formation in the Soudan mine appear to be related t a series of complex folds developed in a single belt of iron-formation. Strong folding in the iron-formation is in contrast to the scarcity of recognizable folds in the greenstone. The ore occurs in the iron-formation as replacement deposits of hematite. The occurrence of ore shows stratigraphic control by the jaspilite facies, and other controls include intrusive contacts and structurally thinned portions of the iron—formation. The origin of the ore is suggested as hydrothermal. �27 MAGNETIC ANOMALIES AND MAGNETIZATION OF MAIN MESABI IRON-FORMATION Gordon D. Bath and Ge.ore M. Schwartz U. S. Geological Survey, ?nlo Park, Calif crnia University of Minnesota, Minneapolis, Minnesota It has long been known that the magnetic effects of the Biwabik iron—formation are complex. It was not, however, until the dLstrict, along with most of northern Minnesota, was mapped with the airborne magnetometer that the full import of the complexity was realized. Large negative anomalies appear where positive effects were expected and positive anomalies appear offset with respect to the geologic map of the formations. As a result of the problems of interpretation encountered, the United States Geological Survey wtth the cooperation of the Minnesota Geological Survey started a detailed research project to attempt to explain the anomalies not only over the iron-formation but over all the igneous and metamorphic complex of northern Minesota. Following are some of the results over the Biwabik iron—formation. Negative magnetic anomalies over magnetite-rich Biwabik iron— formations have been explained as resulting from the low angle of dip which places the formation almost at right angles to the earth's magnetic field. The strength of the earth's field is reduced by the demagnetizing effect of the formation to a degree that the thduced magnetization is less than the remanent magnetization. A direction of remanent magnetization, one that is generally along the bedding planes of the formation, produces the magnetic lows found over the tops of the strongly magnetLzed members. Ground magnetic traverses show the effects of this near-horizontal direction of remanent magnetization. The magnetic lows are much greater in ground an air traverSes over the magnetic taconites of the East Mesabi range. The tendency of alignment of magnetization direction along bedding planes suggests that changes in dip angle would make significant changes A ground profile over the in the character of the magnetic anomaly. Ironwood formation near Mellen, Wisconsin, shows an anomaly that is similar to the one that would be expected for a steeply dipping Biwabik iron-formation 'with a near-vertical direction of magnetization. �28 MAGNETIZATIONS OF IRON-FORMATIONS AND IGNEOUS ROCKS OF NORThERN MINNESOTA Charles E. Jabren U. S. Geological Survey, Austin, Minmasota Measurements of the physical properties of oriented rock eampies co1lect in northern Minnesota show irregular magnetizations for iron—format ions and granites, and. more regular magnet izat tons fr diabase, and flow rooks of the Duluth gabbro comp4ex. the gabbros, The directions of remanent magnetizaUon of the iron-formation are irregular in azimuth but have an average inclination that is close to the plane of the bedding of the formations. Mesabi iron-formations with high magnet ite contents have remanent mcments several times their induced moments, but Soudan-type iron-formations have induced monts that are greater than tbeLr remanent moments. The majority of the gabbro, basalt, diabase, and granophyre samples from the Duluth area have a remanent magnetization with an azimuth of about 2900 and an inclination downward of about 35°. Twenty.-nine sples from seven strongly magnetized diabase outcrops have an average moment of .01 cgs with 288° azimeth aftd 36° inclinatin. Their average susceptibf.lity is 0.003 cgs. Fftyeight samples of Giants range granite collected southeast of Ely show a dotward but scattered direction of remanent magnetization ranging in intensity from 0.0001 to 0,001 cgs. �29 TEE OC RRENQE OF CARBONATES OThER THAN IRON AT DEPTh IN LAKE ST3PEIOR IRON FORNATIONS Pickands J. Royce Mather & Company, Duluth, Minnesota Wide1y sepaated, steeply pitching Lake Superior iron ore bodies enconter an increase in calcium and magnesium carbonates at depth. These carbonates ili voIds in the iron ore, lowering the grade of the iran with a corresponding rise in lime and magnesia. When these contaminants beco sufficiently abundant, the iron formation no longer contains ore even though well oxidized and leached. On the Gogebic range there is evidence that these carbGnates have been replaced by iron oxides at depths of more than 3,000 feet. to indicate that, after the ore was formed, calcium This would and magnesium carbonates were emplaced. At some later time the contaminants were remQved from the top downward. Apparently, in several localities, this removal was aceompanied by replacement in which iron oxides were substituted for the carbonate minerals. At such places very rich oxide ore bodies result, cut off at depth by interstitial carbonates as yet unremoved from the ore. �STRATIORAPHY ANt) STRUCTURE OF THE MeCASLIN QUARTZITE REGION OF NORTHEASTERN WISCONSIN Joseph 3. Mancuso Michigan State University, East Lansing, Michigan The McCaslin Mountain district lies along the parallel 45°22' north latitude aid beten the meridians 88°il' and aaG48t west longitude in northeastern Wisconsin. occupies parts The of Marinette, Langlade, sorest, and Oconto counties and ontain district the MeCas i in Mountain quart zite, the Thunder Mountain quartz ite and the complex of border rocks associated with the quartaites. The district covers an area of approximately 373 square miles. The rock formations and their succession beginning with the youngest are shown in the following table: Pleistocene Glacial drift Unconformity High Fails granite Intrusive contact Hager rhyolite porphyry Unconformity Precambrian McCasiin quartzite Unconformity Waupee volcanics and basement complex The broad regional structure of the McCasiin district can best be described as the north limb of a large synclinal trough., the south limb of which rises in the vicinity of Mountain, Wisconsin, approximately 15 miles south of the main McCaslin range of hills. The axial line of the regional structure trends east-west to N,60°E. and plunges slightly to the The High Falls granite terminates It exhibits intrusive the structure to the north and northeast, relationships to the rocks of the McCaslin district, showing evidence of invasion by a combination of the processes of forceful injection, stoping, and assij1il4tion. st. �31 INCREASI:NG ThE RESOLVflG POWER OF GRAVITY MAGNETIC OBSERVATIONS AD William J. Hinze Michigan State University, East Lansing, Michigan Observed gravity and magnetic anomalies normally consist of the sttperposition of effects from two or more sources. This may seriously hamper the 1oation and quantitative study of interesting anomalies. As a result the first and most important step in gravity and magnetic analysis is to separate the anomaly into its component parts. One method of increasing the resolving power of gravity and magnetic anomalies, and thus of separating anomalies into their component parts, is to project analytically the observed anomaly to what it would be at a horizontal level closer to the sources of the anomaly. This downward continuation method is based on the general rule that gravity and magnetic anGmaliea decrease in areal extent and increase in magnitude as their source is approached. Standard methods of downward continuation are difficult and timeconsuming to apply to most mining and regional geophysical surveys. However, an approximation method, based on Peters' Solution of the upward continuation problem and a method of finite difference approximation to Laplace's equation assuming two-dimensional anomalies, greatly simplifies the problem. Calculations on ideal examples suggest that the accuracy of this approximation method compares favorably with standard methods. The usefulness of the method in increasing the resolving power of gravity and magnetic observations is illustrated by theoretical examples and a case history dealing with an iron—formation in the Lake Superior region. �32 GEOLOGIC INTERPRETATION OF AIRBORNE MAGNETOMETER PROFILES ACROSS LAKE SUPERIOR Edward Thiel University of Wisconsin, Madison, Wisconsin A Varian proton precessional airborne magnetometer scheduled for use in Antarctica during the 1959-60 field season was test flown in the Lake Superior region during October 1959, Four mag netic profiles aroas Lake Superior were obtained, Two additional profiles were run over the Lake Superior syncline to the southst of the Lalce. The correlation øf magnetic variation and geo]ogy obtained over this known geo3ogical structure on these two profiles served as a guide to interpretation of the four profiles across the water—covered region. The magnet ic pattern obtained over the baa ic Keweenawan lava differs sharply from that of the adjacent sandstone formations. On this basis it is possible to. infer the location of geological contacs beneath Lake Superior.' flows �33 IRON DEPOSITS IN CABON, EQUATORIAL AFRICA Gilbert L. Hole Bethlehem Steel The Company, Bethiemen, Pennsylvania iron deposits in Gabon are associated vith Pracbrian sedimentary iron—formation that, through the leaching of silica and the solution and redeposition of iron oxides, baa been enriched to large concentrations of high-grade iron ore. The unathered ironformation is for the most part a laminated roc called itabirite containing hematite, magnetite, and quartz. There ts a little silicate material, but carbonate minerals have not as yet been found. The formation is strongly folded, and steep dips to the east are generally the rule. The ore bodies are related to the surface rather than to the structure of the underlying rocks, the ore zones conly tran secting the bedding of the itabirite at steep angles, Exploration to date has indicated a reserve of several hundred million tons of direct—shipping, open—pit ore running 62 to 64% Fe and 2 to 3% SiC)2, and it is anticipated that an additional significant amount will be proved through further exploration. The ore is friable and soft and will require agglomeration. Rvntual development of these deposits will requ4re construction of approximately 450 miles of railroad through rough jungle country, much of which is wild and uninhabited. � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1960 Description An account of the resource Institute on Lake Superior Geology, University of Wisconsin, Madison, Wisconsin. April 14-15, 1960 Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1960 Contributor An entity responsible for making contributions to the resource John W. Allingham Russell C. Babcock. Jr. Lloyal O. Bacon Robert G. Bates Gordon D. Bath Richard C. Beard Thomas E. Berg Robert F. Black Lewis M. Cline Gerrard L. Coetzee Carl E. Dutton Thomas E. Hendrix William J. Hinze Gilbert L. Hole Charles E. Jahren Robert W. Johnson Jr Elizabeth H. Kissling Frederick L. Klinger Gene L. Haberge WIlliam C. Luth John W. Mack Joseph J. Mancuso Robert P. Meyer Willard H. Parsons Josiah Royce Kenneth A. Sargent George M. Schwartz Robert E. Sloan John S. Steinhart Edward C. Thiel James Trow George P. Woollard Justin Zinn Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/44f7124d14f12414cf6d4607d9d50899.pdf 596272a38cfdcea234c5d67d1589e6f5 PDF Text Text -&IXTH ANNUAL MEETING INSTITUTE O LAKE SUPERIOR GEOLOGY • APRIL 27th 29th, 1961 SNYSORED13' I tKEFJEAD BRANCH - C NLWJ \N [WI ITUTr OF MENING & METALLURGY 1 EL- — ON'IAfl-iO-DFI-TAhTMI \T OF MINLS PORT EIThJR& FORtW4LE1 \F ONTARIO �SIXTH ANNUAL MEEfl'ING OF TE OF lAKE SUPERIOR GEOLOGY iNSflTflE April 2?, 28 and 29, 1961 PRcOHAM. Provl.ncial Rooms Prince Arhm' Hotel Thurs4ay, April 27 Chairman E• 8,30 A.M. 9.30 10.30 11.00 11,20 1l.O G . SE$SION I Abàtract Na. Pye Page. No. Registration and Social Hour Address of Welcne WL.CS Greer Business Session .Henry Lepp Glimpses of the XXI Injernational a Geó1ogca1 Congress -s A. ic. Snelgrove Geocheidcal Anomalies in Forest Floor Material I Progres Report D.fl Trd1ey The Petrology of the Ge4o Nine R.C..Ee 'ay An Investigation of Sçme GoldQüartz Veins . , V.. Oja iS 18 12 Institute Luncheon 12.30 PJ. SESSION II Co.iChairmen 2.00 PN 2.30 3.00 .3O .O0 Henry Lepp, A. K. .Snelgrova Sublacustrine Topography of Eastern Lake Supe'ior Jack Parker Recent Contributions to the Late and Recent Geological History of Lake Superior John }. Zwnberge Ve1octy and Isotropy Stwltes of Pre cambrian Lameflar Forination2 (to be Dreserred by G, Secor) D. W, 4erritt (o'fee and biscuits (no charge) Granitic Rocks of the Pembine Area, Northeast Wisconsin - J. Allen Cain Tectni Analysis of Some Precambrian Rocks, Horn Area, Bighorn Mountains, John C. Palmquist Wyoming Lithology of the Seine Series in the Vicinity of Crilly, Ontario W. L. Young Friday, April 28 Co-Chairman 6 13 19 SESSION III Henry Lepp, Gerald Anderson 9.OQ A.N, Types of Iron Formation in Western Ontario 9.30 Geology of the Nakina Iron Froperty, 3.0,00 30 ar4 Their Sign ficanc 0. G. Suffel OntariQ W T. Swensen Geology of East Lake St. Joseph Iron Formation A, T. Avison and J. .F. Wbite 4 16 17 3. �Friday, April Abstract No. SESSI0N III 8 Page NQ, 10.30 A,M. 100 Coffea and b±scuit?s charge) The. Erce Lake Iron Formation, Red Lake Mining Division, Ontario •. M. We Eartiey Some PetrQgraphic and Chemical FeatureE 11.30 3 of the 0iinlirtt Iron Range, Pt Arth Area W. W. Mooz'ehouee Institute Cobaiien -' (no Luncheon 12.30 P.M. Trevor Page, R. V. Oja 2.00 P .N. Rem nent 2.30 in recambrian Banded W. A • Gross and D W. Strangway The Use of the Dp Need'e wi1b Specia3. gnctsm and Orgin of Hard Hematite Iron Fortnation Reference to Magnetic Taconite Exp1oraiion — william J. Hne Manganese in the Menonirise Iron Rang€i, Niàhigau (to be presented by gaul Zirnmer) Paul Zimner and G icnatra 3,30 Corfee and bisc4ts (no I 20 Iron The Distribution of Manganese in Sedimentary Iron FoririatjQna and Associated Rocks — ffnry Lepp The Thterpolat±on Parabola Applied t 5e002x1 Deriatve. Interpret&tion — Lloyal 0. Bacon 00 8 charge) Rep1aoment Texture in Negaunee Formation E. L. Beutner I.30 7 b 9 2 �UTHORS Geologist, Ungac; Iran Ores Mxtrea]. A. T. Avison Geologist, Geco Nines 'Manitouwadge K. Abe]. Lloy]. College of Mining and Technology, Houghton, Michigan Michigan 0. Bacon W. Bartley B. L. Beutner R.C.E. gray j Allen Cain . Re Gross Abstract 'a No. UI Consulting Geologist, Port Arthtr Chief Geo1ogist Jones & Laughlin StOl Corporation, Pittsburgh. Pa. Chief Geologist, GecoMines, Deprtment of Geology, Northwestern University, Evanstn, flhlnois 6 Geology, 7 Assistant Professor, Department of University of Toronto Department of Geoipr, Michigan State Univerglty, East Lansing, Michigan C. Kustra Nie1gan College of Mining arid D. W. Merritt Tehnology, Hôüghton, Michigan Associate Professor of Geo)!igy, Univezsiy of Minnesota, Duluth Geologist, The CaliforuiC. Can7 in New Orleans, Louisiana W. W. oorehouse Professox' Department of Geology University of Toronto Consulting Geologist, Port Arthur Ray V. Oa Geologist, Geco Mines, Manitouwadge V. T. Onodera Jo, O Palmquif .Departmont of Geology3 State Univeri.ty of Iowa, Iowa City Michigan College of Mining and Jack Parker Technology, Houghton, Michigan A. K, Sneigrova Professor, Michigan College of G 0. Suffel Aasociate Frofessor Department of W. T, Swensen D• Strangway F. White D0 H. Yadley 1 U, L. Young P J. W0 Zer H. Z'umberge 3 Manitouwadge U. J. Hinze Henry Lepp 2 8 20 9 10 11 12 13 ilL Mining and Technology Houghton Geology, University of Western Ontario, London Asdstant Vice President, The Anaconda 16 17 oIiipany (Canada) Lirnit,e, TorontG Geophysicist, Bear Creek Research 7 Mining Company, Denver, Colorado Ltd., .. Geologist, teep Rock Mines 1 Steep Rock Lake Engineer" Associate Professor of 1ining ing, University of Minnesota, MinneapoliS 18 — Ass±stant Profes sor, Department of neology, Carieon College, Ottawa District Geologist, The M. A, Hanna company, Iron River, Michigan professor, Department University of Michigan, n Arbor of Geo1o 19 20 21 -• �:i. GEOLOGY 0? THE EAST LAKE ST. JEPH ThCI WOPY A, T, Avison and J, F White Magnetite iron formaton occurs in a belt of meta. morphosed Keewatin#ype se&Lments at the east end of Lake at. Josepk in N th-centval Ontario. Two major hwiz ens and nuirm smaller lenseà of iror formation re interbeddéd with a series of quarbz''biotite schists and tLc chlorite and anetifrous schists near the north áomtait of an igieoiis mass of granite and gatbro, The two major h'izone vary betweo 3.O and 1180 feet wide at 8tU' face and are believed to be made up of closely interfthgered lenee rathex than widespread regiilez' beda. �2 THE ThTERPOLPTION PAR&BOL& APPLIED TO S CO DEIVATIVE IEPREL'AT ION Lloyal 0. Eacon • • Numerical second derjvatLe forpuIation is derived for one dimensional (profile) arid tWQ ditnensioua3. (surface) data. Coiu' parison with other methods of second derivative calcjlattrn is px'e.. sented for several minezal exploration areas �THE BRUCE LP1KE IRON FORMATION, RED LAKE MINING DD1ISION, ONTARIO M. W Bartley The history of exploration for treatable iron 'ormation at ruce Lake, Red Lake Mining Divi3ion,, Ontario is described a1cng with a brief review of the general ratigraphy and strueturee The Keewatin..'t37pe iron fonnation has been deliz:ieated by geological nd geophysicai riapping, and diamond drilling has outlined two stthstanr tial iron. çre deposits from which a des±rable peflstized product can be dx'ved. ( �RPLkCEMENT TEXTURE IN NEGAUNEE IRON FORMATION E L. Beutner Studies and Qb5ercations which were iade during th past fifteen years in the curse of field mapping, exploration drilling and mining in a portion of the Marquette Range south of Negaunee, Michigan, point up sonie interesting relations between charatsrstica of the iron romation, geological structure and the localization of soft irn ore deposits Evidence here seems to indicate that much of the. iron forination had undergone oxidation before ore forming processes were actIve and possibly before completion of iiastrophisn, Secondary oxidation, leaching, replacement and sometimes actual inioval of both iron and silica occurred in some zoneLs which had been strongly fractured through folding or faulting ar4 along the contacts between the von formation and in— trsive ocka. Where waters circulated through such disturbed areas they 1et their mark in a distinctive spotty or "leopard" texture which is superirrrposed on the norma]. straight bedded iron formation. Tha avenues of circulation nay be traced from the present surfae through steeply dipping fault zones to the lower thin bedded part if the iron formation where the soft ore bodies are localized. The fact that the hanging wall iron formatibn of many of the ore deposit exhibits the porous "leopard" texture suggests that the game solutions which were responsible f leaching and repaoement in the iron forxna.. tiori may also have brought about nearly completu removal f silida and enr±c}ent o.t iron in e1eted structm'a). situatjox to form the high grade ires, I �THE PPROLCY OF THE QECO MINE R,CE. Mo'e Bray, LK. Abel, V.T. OnQ4e'r. detailed petrographic studies o the rocks with the Geco cop zinc ore deposit at Maz4touwadge,. Ontario, thafl waE previousIy possible have establJshed the sedi. meritary Qrigin of the grey gneiss, The variations in the quartz. ass ociated muacevlte schist and in the horn.fel are escrbed, The intrusive quartz dirites and pegrnatjtea are also described.: The rntainorphic minerals connected with the re zone are discussed. �6 PREGAMBRIAN GRANITIC COMPLEX OF NORTHEASTERN WISCONSIN J. Allan Cain From an area oX soiie 350 square miJes mapped within th Wiconsin Pre canbrian Qorriplex, a rock..uriit was selected for more de ta structural and modal analysis. This unit the Newingham Granite lies jirmiediately 3djacent to the town of Pembin, is .sci$ O square miles in area1 and has intrusive contacts wi±h greenstone, bjotite neiss and horriilende gneies. Nodal data from 70 specimens- for quartz o1or index, feldspax ratio (potash. feldspar/plagioclase), and total feldspa', as well as spific gravity, were analyzed. on..orthoginal polynoird.aJ analycts was used — via 1.3. 650 - to compute linear and quadra tic trexid!..surface8 and deviations for each variable. A comparison of these results with those *tained by lthitten from his similar £tudy of the "older granite" of Dneal (Ireland) indicates the potenttal petrogenetie significance of trend—srn'face analysis. I �7 REMA.NENT MAGNETISM AND THE ORIGIN OF HAiti) HEMATITES IN PRECAMBRIAN BANDET) IRON FOIThIATION W. H, Gross and D W. Str.ngway Because hematite is a mineral with a high degree of znagnetio stabiUty t was considered possib]e that a study of the reman t maget. ierrx of hematite ore bodies In. iron forration 4ght add to a knowledge of their origin. To test this possibility, a number of ,riented spLmens an iron were collected from two hard hematite ore bodis that ocem' formation near. Fort Gouraud, Mauritania. Or of these ore bodies is an elongated ens of hard hematite which occurs in a steep plunging "S' shaped fold. The lens is roughly con cordant 'with the trend of the bedding of the surrounding iron formatiofl. and it is known to extend to a depth of at least .7S0 feetbeiow the present surface without any detectable change in physical or chemical properttee. It was found that the principal directions of remanerit magnetizatoii must have been formed in the hematite whefl the. beds were essentially flat. This is interpreted to mean. that' the bulk of 'the hematite in the ore is either syngenetio and was formed as an Iron rich horizon during sedimen" taton or it was formed by leaching of the flat-lying iron formation. The steep inclination of the magnetization in the beds when. they have been "unfolded" to the flat position suggests that the ore was formed in the Precambrian when the earth's magnetic pole w:as located in Northweatei Africa, magnetic direction on one of the limbs A Second rather is thought to indicate the Lormation of secondary hematite that was formed either by reworking of the primary hematite or by introduction. of hema-. tite into the ore zone at the time of folding. If the ore Is essentially syngenitic, prospecting for additional ore bodies of this type at Fort Qouraud should be governed by a knowledge of the primary features in the oigina. basin of deposition. A second ore body is composed primarily of soft hematite that has a hard hematite capping.. The soft ore is relatively shallow in depth ar4 .s discordant 'wth the bedding in the underlying iron formation, The magnetic dixections in the hard hematite capping were lagely random but hae some preference towards the present magnetic north. These results suggest that this type of hard In re].ati'ly modern times. fii was formed by leaching It is concluded that the hematite ores at Forb Gotiraud have had a complex and multiple origin. �8 USE OF T} DIP NLE T}E WITH SPECIAL REFERENCE TO MkGNETIC TACONITE William J, PLORAT ION Rinze The dip needle, crie of the oldest of geophysical explora. tion instruments, is skill beig used as an ecploratiori tool particu larly in the arch for magnetic taconite ores0 However, the highly distorted magnetic fields associated with these ores oten produce misleading dip needle anomalies due to the interaction of intensIty and inclination effects0 tase histories and a laboratory investiga-' magnetic fields illustrate the profound. effect that both of these magnetic yariables have on dp needle. readings • Results of a laboratory investigation indicate that large negative normal settings nay be used to subordinate the effect of inclination over high ±ntensit ranges thus forcing the dip needle to give a clearer picture of the rnagnetic character and distribution of the rock formations. The period of oscilJation of the swinging dip needle, which decreases as the vertical magnetic intensity increases 3fld as the inclination decreases, can also be used as an aid to the successful geological interpretation tioia employing controlled of dp needle tnoaliea. Studies indicate that temperature, orientatior, and leveling variations normally encountered in field operation of the dip needle result in negligible errtx*s and a stuclT of dip ieedle reading method indicates that the optimum, reading method varies the requiremezts and conditions of the surveys but that the reading rrthod based on the ritnetic meanof the second, twice wit l i the and the fourth reversals third, most universaU I acceptable. f the oscillating dip needle �9 TH DISTRIBUTION OF MP3ANESE IN SEDINENTARY IRON FORMAT IONS AND ASSOCIATED ROCKS Henry Ipp The average Mn:Fe ratio f Precambr.an iron formations is O.O3! which is essentially the same as that of the average crystal. line rock (' .028) from which these formations were derived • Post Pre. cambrian iron formations, on the. other hand, have an average Nn:Fe indicatIng a pronounced geochemical separation of iron and ianganese as compared to the crutal average. The difference in Mri:Fe of the two age groups of iron sediments nay be due to differences in depositional eivfroninents ( dizing. environment favors the separation o! Mn and Fe, rbonate fie]d does not) ratio of 0.007, ratios en.ces In the nature of their source rocks, or to differ. In Precambrian Iron fornmtions, the oxide horizons have considerably lower' Mn:e ratios than the c'bonate..silicate horizons. There appeai's to be a correlation between Mn:Fe ratio and CQ2 content, The distribution of Nn:Fe ratios for analyses from the Quyuna range 18 bimodal • The rorinangan.U'eroua sections of this iron tr ratio of an show lower than norma'. MzuFe ratios whereas the reverse s for the manganiferous horizons, The average iralu of the Mn:Fe iron formation nay provide an indication of whether or formatIon nt sedimentary manganese deposits can be expected in the same sedi. ment1ary sequence, �10 VELOCITY AMISCIrR0PY STUDIES OF PFECAMBRIAN WLLAR FOR1ATIONS Donald W Merritt A prelimnary field investigation was made of seismic wave velocity arilsotropy in lameilar formations. Results of the shallow seismic refraction surveys in seven different localities on Precambrian metasdimentary and inetaigneous rocks cornprising eight different lithQlogies inciudin schist, granite gneiss, banded iron formatiO, slate and per±dotie altered to serperitiriite show that velocity anisotropy is meaurable in the Zi4d and nay be useful in delineating structural orientation in buried fonna.. tions, Sei'mic vave velocities in steeply dipping formations characterized by beddiig, jointing, cleavage or fractures were foufld to be faster in the directjon parallel to the fractures than perpendicular to theni The ratias between the seirrd.c wave veio'' cities parallel to and perpendicular to these feat1res approached values of two to one, I �SE PETRORAFHIC AND CHEMICAL FEATURES OF THE GUNFLINT IRON RANGE PORT ARTHUR AREA W. W. Moorehouse be results of about 100 spectrochemical analysss of iron fømtion and asociated argillites from the Gunflint and Mesabi ranges are suzmnarized and compared with simiLar ana1yes of ancient and recent marine and non'-marine sediments of varioi typese The results of these analyses are consistent with a marine or bracki3h-.water environment of depo8ition of these iron fcrrmation. The significance of various characteristic textures of the several facies Qf the Gunflint is revieied. The granules ai4 other features of the taconites, as well as their field oharcteris-* tics are indicatIve ef active or tebu1et conditions of depos±ti5n. The variations oftei encountered ri the mineralogy f the taconites point to the mixing of the products of local regimes of varying h and pH. The influence of diageriesis and itamorphism in modifying the mineralogy and texture is discussed. It is voncluded that they have not seriously disturbed the aigriificaxzt environmental criteria. The petrog2'aphic features of the other main facie3 of the Gunflirit are corzsidered, it is concluded that these result from variations in depth, turbulence and organic content in the environ-' merit of sedimentation. Textural and compostiona1 features bearing on the role of volcanic contributions to the accumulation. of the sediments of the Gunflint cQnclude the discussion. I �32 ANVESTIGATIONOFSO GQQUARTZVEIT R V Oja ijwestigation was conducted ort 30 o' 70 ore-. and non!ore.'bearing quartz veins in one section of one of the gold -jnes of the PorQupine Camp, Qntario. Although all 70 veins had been exposed and developed by underground headings, not all con-u This tamed gold in qu'antities'suiTtcierrt to make ore Since both orend non-.ore-beqring quartz veins were identical in appearance in iamond drill interectionD and in the underground eXpQsm'eB, the perpleirg decision, "Should the vein be develope4 further?' zearly always h.d to be faced. This research, therefore5 sought to establish a means Qf distnguishg between ore- and non-.ore-.bearing quartz veins by petrographic, dcrepitation and spectrographic techniques klthoigh it was discovered that ore-.bearing quartz contains more liquid in.. clusiorts and decrepttates 11$ to 3i% more than the non-.ore-.bearing çucrtz, sp much overlap exists in the results of these observationa categorized with as'surance. so that no single secirnen Sir.ilarly, no conclualve differences were revealed by spectrographic cnbe irrve stigation. After reconsiderIng the methods of quartz vein formation the gold, and gold introduction, it is concluded that, apart there need be no major d. erences in the chemical or piysical pro" perties of the ore— and non.orebearing quartz veins considered in this iigation, �33. TECTONIC ANALYSIS OF SOME PRECAMBRIAN ROCKS, i IGORN MOU1TAINS WYOMING Johii C, Palinquist A Laramide blocls"like uplift of the Precambrian basement. resulted in the formation of a faulted mountain. niasa cveririg approxi.. rnatély 27 equare miles, extending southward from the centraL Bighorn unit. The core of this uplift contains complexly folded, £oliated hihgrade metamorphic. rocks Precambrian rock types include pegmatite, anphibolite, calc—siUcate rock, fldspathic rotk, btotite shist, marble, banded ironstonø, quartzite, varieties of garietiferous rock and amphibole' rQC1S in addition to the predominant gneiss. Schistosity, inineraJ_0g1. cl and lithological. layering are conformable throughon the complex with c±oss—cutting pegmattes being the çuly exception. These rocks are believd to have originated from reginaJ. metamorphism and later alkali meta.somai4,vi of supracrustal. rocks. Alkali inetasomatism, apparently a post-tectonte event arid perhaps a late stage of the regional rnetamorp1iism, culmirated in pegmatitizatot.. The staurolite'. quartz s'ubfacea of the almandinei.amph±bolit,e facies is iidioaied. The internal structure of the metamorphic rocks is dominated by a complex anticline plunging to the norrorthwest. Foliation, lineation, reiaton of minor folds and distribution o mapped uiits all point to the existence oi' this fold, but the preoise g&ometryof the fold is elucidated ory after a study involving methods of st&tistical analysis and tectonic profile construction, This study reveals a closed, slightly overturned cyiindric4 anticline dth. planar limbs, Measured lirieatiori cqrrespo4s to the axial line as determined from statistical analysis ot foliation data, and is, there'.. fore, b.Uneation, Sediinentary..covez' structures are believed to result from passive draping cver active basement blocks. The blocks are bounded. by the Horn and Tensleep faults, The attitude of the Horn fault parallels foliation weas the Tensleep fault appears to be a rejuvenated Pre. cambriaxt fault, These relatiàns demonstrate that the strictural grain of the basement may influence later deformation. I �SISBIACUSTRINE TQPCXRAP}1T OF EASTERN LAKE SUPERIOR Jack Parker Interpretation of recent echosoiinding taken by the IJ,S. Lake Survey indicates that the Lake Superior basin has been ice out of relatively soft rocks,. and that inoraines excavated on the south shore hold the water at its present level, Long, nà'rw vaUeys, as much as 700 feet belcw sea level, exteid as in a northau"south directions rrruch as So by inils ros±on of hard arid soft Dock8 and the general liiiiits of lavas, sandstones, and glacial drift, the 4irection of ice mcvernent and. the major faults. Differential shear zones pern.tts mapping of I Of �GLflSES OF T} XXI I1'TERNATIONLGECLOGICAL CONGRESS A. K. Sneigrove A travelogue of the Copenhagen Congress in August, 1960, by one of N.tQhigan Tech's official professional delegates. In additiou to attending the meetings, the speaker yiited the Western Noegian Fjord oouxxbry, and participated in geological exeureicns, in the 0810 area &td in the rnird.ng cezitera of outbern Norway �T!?ES OF IRON FOR1ATION IN WE$TERN ONTARIO AND THEIR ORIGINAL ENVIRONMENT G. G, SiiffeJ. A detailed study of published literature mentioning or describing sedinnta7 iron formation in Western Ontario has con. firnied that there are four types aufficiently different n character and lithologic arid structural envfroruiient that they can be readily distinguished. The Patricia and Port Arthur Mining Div±sions provide a north.south section across the Superior province in Canada. It is suggested that the iron forniations were deposited. in enornents compatible with those supposed to occur during a sequence of geo. synclinal sedinntatioi with the development of jsland arcs. It seems conceivable that the IIars hail Lake series and related rocjcs of Coutchiching type represent ancient shelf deposits, the oldest rocks in the Province The Keewatin type in almost cer-. ainy lagoonal marine, the iron. proba'bly originating i'rc volcanic emanations, The Windigo1an or imniskaming in closely associated with producte of mechanical erosion of eugeosync3.inal rocks. The origin of the iron may have varied with time and. place. The Animikie formations are imiogeosynclinal, blQnging to a new arid uncompleted cycle, Although this area is upposed to represent one of the original continental nucleil, considerable evidence suggests that still older land masses exited, as yet unrecognized. I •1 �TYPES OF IRON FOINATION IN WESTERN ONTARIO AND THEIR ORIQINAL ENVIRONME G. G, SuXfel A detailed study of published literature mgntionirzg or de3cribing sedirnentar-y iron formation in Western. Ontario has con- firmed that there are four types sufficiently different in oharacter and lithologic and structural environment that they can be readily distinguished. The Patricia and Port Arthur Mining Divisions provide a orthisouth section across the Superior province in Canada It is suggested that the iron forT1ations were deposited in erivirormients conpatible with those supposed to occur during a sequence of ge° syciinal sedimentatin with the development of island arcs. It seems conceivable that the Marshall Lake series and related rooks o Coutchiching type represent ancient shelf deposits, the oldest rocks in the Province, The Keewatin type is almost er tainy lagoonai. marine, the iron probably originating from volcanic eirxiations. The WindigoTzan or Tirniskaming type is closely associated -ith products of mechanical erosion of eugosynolinal rocks. The of the iron may have varied with time and place. The Ariimikie formations are iniogeosynciinal, belonging to a new and uncompleted origin cycle. Although this area s suppoed to represent one of the original continental nucleii, considerable evidence suggests that still older land masses existed, as yt unrecognized, I �17 GEOLOGY OF THE NAKINA IRON PROPEIY1 ONTARIO W, T, eisen The Anaconda Ccmpany, through its wholly ned aub sidiary The Anaconda oinpany (Canada) Ltd., has investigated optioned arid partially developed a large tonnage of iron ore amenable to magnetic cocentration0 The reserves are located in north centra1 Ontario and ccur within a twenty.'two mile belt b!' layered arid intricately fo)ded metamorphic rocks close to the north contact of an igneous complex of gz'anite aid pegmatite. There are two main ore deposits.0 Bx'iarclil'fe. is a steep to vrtially dipping body 100 to 500 feet wide and over a mU long. The Tw Nile deposit is flat dipping and confined to an open, asymretric syricline; it is approximately a in:tle wide and 2S0 to 1400 feet thick. On Its flat easterly punge it i aaucer1ike shape and is emanable to open-pltting for an east-west distance in of several thousand feet. Its further extension has been mdi" cated for at leaat three nd.la by xrgnetometer wor1 in conjunobion with diamond drill tests. �18 GEOCHEMICAL ANOMALIES IN FOREST FLOOR MATEEIAIS A PRGRESS REPORT fl H. Yardley Geochemical investigations of forest duff (htunus layer) near ZLy, Minnesota demonstrate that CNi inineralizai. tion in wder13ring gabbro is rZLected by the Ci-Ni content of the forest. duff. The anomalous pattern is more erratic than the pattern in the underlying till but does identify a target zones 8anpLing of forest duff is faster than soil sampling but further simplification of both analybtl arid sanp].ing methods appears neceasary before recommending the method for gerra1 app), cation.. �1, ITHOLOGY OFT}SINE StIES LLYrARI W. L. Yowig The .&tho].ogy of the Seine Series is diused arid the three princ±paL fac.e-s are suggested. Petrologic and geocheincal analyses ef the matrjx of the Seine "Conglomerate" compare favol2rably with the nearby Keewatin. lavas, suggesting a volcanic matrix for the Seine "Conglomerate". Lack or sedimentary features within the matrix: suggests a non.sedimentaz'y origin. It is postulated that the natrlx was a voLcsc flow or glowing-avalanche-'tuff which picked up and ircor.. porated boulcers while it was being laid down, and must, therefore, be thought of as a volcanto r?.ther than a sediment. If the Seine is to be used as a mrke'formation, then, it is impprtant to recogzize that the lithpogy may change from a "boulder conglomerate" to a "sericite..ohlorite 5Chi5t" in a short distance. Near Crilly the Series dips under the Keewatin volcariic6 At Nine center the Series is intruded by the Bad Vermillion granite, It was concluded that the Seine Series is of Keewatin age. I �20 MA.NQANESE NThERALIZATICN IN THE CANNON IRON NINES, IRON RWRaCRThL FALLS DISTRICT ,KECHTG P. W. Zier arid C. R, Kutra Nngane.sa occurs in only one mine in this area in quantities large enough and with gzade high enough to make & manganiferous iron ore product. This paper describes the mineralogy of this mangantferous ore body. The primary manganese mineral s hausmannite accompanied by such mzinezls as manganite, pyrolusite, rhodochrosite, braunite, ar4 rhodordte, as well as email amounts of i.ydrohauannite and maanese'ich sussexith. Other minerals occurring with the manganese mineraii. zation besides the ate, limonite, and goetbite are calnite, siderite, gypsum, qimtz pyrite, chalcopyrite, native copper, chrome, montmorilionite, and other clay minerals such as kaolinite and auxite, Although rrjanr of the above minerals strongly suggest hrth'othermal waters, no firal conclusions are drawn at this time as it is felt ean be made0 ( much more rork must be done before 4euch. concLusione �21 PROPOSED CORING IN LAKE SUPERIOR James I-1 Zumberge Shallow btton cores arid fathometer records óbtained from Lake Superior in 1953 provide the basis for seleothig sites for a coring program in 1961. Cores will be obtaix4 fz'oni several locations in the western, central and eastern parts or the basin through the use of a rotary drilling rig mounted on a ship aquipped to drill in water 1300. feet deep0 Fathometer records frQm a previous cruise reveal areas where more than 60 feet of laoustrine sècthnent occur above denser ntteria1, Glacial till gives the sa fathometer signal as Pro-. c'.mbrian bdrock, A core retrieved from a depth of 612 feet, 13 miles east of Grand Marais orf the Minnesota shore, contained 105 lamin-' ated couplets of alternating light and dark silty clay layers with an average combined thickness of 8.5 mm. The lighter layer con-. tains more carbonate than the darker layer, but is almost devoid of pdflen. Highest pollen concentration occurs in the darker layer&0 Other material found includes frosted sand grains, agnetc spherules, arid diatoms5 Laboratory analyis of the cores in which all of these eleineats are iwrestigatad should provide the basis for the geological history of the lake since its origin. � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1961 Description An account of the resource Institute on Lake Superior Geology, Lakehead Branch - Canadian Institute of Mining & Metallurgy, Port Arthur, Ontario. April 27-29, 1961 Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1961 Contributor An entity responsible for making contributions to the resource A.T. Avison M.K. Abel Lloyal O. Bacon M.W. Bartley B.L Beutner R.C.E. Bray J. Allen Cain W.H. Gross W.J. Hinze C. Kustra Henry Lepp D.W. Merritt W.W. Moorehouse Ray V. Oja V.T. Onodera J.C. Palmquist Jack Parker A.K. Snelgrove G.G. Suffel W.T. Swensen D. Strangway J.F. White D.H. Yardley P.W. Zimmer J.H. Zumberge Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/238d4ac647a23bdc878175ce30cd2492.pdf bed7e5202588fbfe694e67fe18680f19 PDF Text Text 8th ANNUM MEETING a fitute on Lake Superior Geoióy o, I cC I';' L11 12, 1962 rI 1t; scy - tti 't1 : -. Sponsored by • Department of Geology & Geological rtngineenng in Cooperation with The Institute of Extension Service t . . n 'ucrngan Coiiege ot Minmg & Technology �!LOARD OF DIRECTORS Dr. E. N. Crneron, Madson, Wisconsin Dr. W. I... C. Greer, Port Arthur, Ontario Dr. Iienry, Lepp, Duluth, Minnesota Dr. G. M. Schwartz, Minneapolis, Minnesota Dr. A. K. Sneigrove, Houghton, Michigaz. STEERING COMMIT'IE1' Dr. M W. Bartley, Port Arthur, Ontario Dr. W. L. Daoist, State Geologist, Lansing, Michigan Dr. C. E. Dutton, U.S. eological Survey, Madison, WiScnsin Dr. J. P. Dobell, Michigan Tech., Houghton, Micbigan Mr. R.obert Edwards, InIandSteelCornpany, Iron River, Michigan Iowa Dr. D. H. Hase, T.iveisity of Iowa, Iowa Dr. R., L. HeUr, Duluth Branch, University of Minnesota, Duluth, Minnesota Dr. H. L James, University of Minnesota, Minneaplis, Minnesota Dr. E. G. Pye, Ontario Department of Mines, Port Arthur, Ontario Dr. P. Tychsen, Wisconsin State College, Superior, Wisconsin Dr. 3. Zinn, Mithigan Stat University, East Lansing, Michigan Dr. J. H. Zumberge, University of Michigan, Ann Arbor, Michigan �EIGHTH ANNUAL MEETING OF THE INSTITUTE ON LKE SUPERIOR GEOLOGY May 10, 11, and 12 1961 Co.!Chairmen: A. K. Snelgroie an4 J. P. Dobell PRQGRAM civil-Geology Auditorium THURSDAY, MAY 10 8:30 Reg.itration Memorial Union Building 9:30 Address of Welcome President 3, R. Van Pelt Biness Session Henry L,epp Chairman - J. P. Dobell 10:30 Current Geological Research i the Palmer Area of the Marquette District, Michigan Jugtin Zinn 11:00 Geological Surveys Pikes Peak Area, Baraga Countr, Michigan Kiril Spiroff 11:30 Petrology of a Pec.mbrian Piuton 3. liai Cain near Pembine, Wiacon1sin 12 - 1:30 Luitch Chairman - L. 0. Bacon 1:30 Geophysical Evidence for the Presence of Kewee-nawan Volcanics in the Area of Upper Michigan be tween Marquette and SuIt Ste. Marie R. W. Patenaude 2:00 Application øf the High Speed Digital Computer to Gravity and Magnetic Analysea R. L. Coon and Peter Wolfe �THU± DAY, MAY 10 2:30 3-3:15 3:15 3:4 Magnetic Investigatios in Iowa A Preliminary Report D. H. Rase Coffee Break Extension of the Normal Distribution to Filtering of TwoDimensional (St.zface) Gravity and Magnetic Data Th Optimum Dip Needle Reading W. W. Johnson* and S. A. Finnegan W. 3. Hinze Method 4:15 Geophysical Investig-ation of a Diabase Dike near L'Ane, R. J. Reuss Michigan FRIDAY, MAY l1 Chairman - M. W. Bartley 9:30 A Regional Verticel Iiitensity Map of the Southern Peninsula of W. J. Hirize. Michigan 19:00 Diagenetic Replacement in Ore of the Empire Mine of Northern Michigan, and Its Effect on Tsu-Ming Han Metallurgical Concentration Footwall Mixeralization of the Osceola Amygdaloid in the Michigan Copper District R. Weege* 1:1:OQ. Induced Polarizatioi Logging in the Search for Native Copper in the Osceola Footwall Zones L. 0. Bacon 11:30 Preliminary Investigation or Late T. VT. Page* Wisconsin Drift North of Lake and 10:30 Superior 1Z 1:30 Lunch and A. Scliihinger D. R. Lindsay �FRIDAY, MAY11 Chairman - J M Neilson 1:30 Precipitation Chromatography in Geo-hemica1 Exploration S. D. Spain 2:00 The Water Prob1em of the Mining. Industry Qf the Upper Peninsula, S. H. Butler Michigan 2:30 Iron Ores of Bthar and Orissa, A. K. Sneigrove India 3:00 Mineral Exploration in the East Glare District of ireland R. W. .Schultz 330 Magne.tite Analysis of Magnetic P. D. Shandley 4:00 Sustptibility - An Investigation of the Remanent Magnetization of the Covi.ngton Dike Indicates speaket C. G Eufe �AUTHORS Page No. L. 0. Bacon C. G. Bufe J. H. Butler J. A. Cain Department of Physics, Michigan Tech., 1 Houghton, Michigan University of Michigan, Ann Arbor, Michigan Geography Departrnent, Michigan Tech., Houghton, Michigan Department of Geology, 2 4 5 Western Reserve University, Cleveland, Ohio R. L. Coons S. A. Finnegan Madison, Wisconsin Michigan Tech., Houghton, Tsu-Ming Han The Cleveland-Cliffs Iron Company, Ishpeming, Michigan 7 D. H. Hase Department of Geology, University of Iowa, Iowa City, Iowa Department of Geology, Mjchigan State University, East Lansing, Michigan Michigan Tech., Houghton, Michigan Lakehead College of Arts, Science and 8 W. J. Hinze W. W. Johnson D. R. Lindsay T. W. Page R. W Patenaude R. J. Reuse A. Schilhinger R. W. Schultz P. D. Shandley A. K. Sneigrove L D. Spain K. Spiroff 6 Michigan Technology, Port Arthur, Ontario Lakehead College of Arts, Science and Technology, Port Arthur, Ontario University of Wisconsin, Madison, Wisconsin Michigan Tech., Houghton, Michigan.. Geology Department, Calurnet & Hecla Incorporated, Ca,lumet, Michigan Michigan Tech., Houghton, Michigan Department of Physics, Michigan Tech., Houghton, Michigan Department of Geology aid Geological Engineering, Michigan Tech., Houghton, Michigan Department of Chemistry and Chemical Engineering, Michigan. Tech., Houghton, Michigan Department of Geology and Geological Engineering, Michigan Tech., Houghton, ii 9- 10 11 12 12 14 15 22 16 18 19 20 21 Michigan R. Weege Geology Depart-ient, a1umet & Hecla Incorporated, Calurnet, Michigan Peter Wolfe Madison, Wisconsin Justin Zinn Department of Geology, Michigan State University East Lansing, Michigan 22 6 23 �I INDUCED POLARIZATION LOGGING TN THE SEARCH FOR NATIVE COPPER IN THE OS EOLA FOOTWALL ZONES L. 0. Bacon A prograzn in cooperation with Calurnet and Hecla, Inc., has been. carried out. to adopt e induced polarization rnetrnd to under- ground logging of exploratory holes. The paper discusses equipment, logging techniques, interpretational methods and results. 7 7 / �AN INVESTIGATION OF THE REMANENT MAGNETIZATION OF THE COVINOTON DIKE C. G. Bufe The irwestigation of the remanent magnetization of the C.ovington dike near Watton, Michigan, was begun in September of 1960, and in the course of tha investigation oriented cores were taken froxi the dike and country rock on both sides., thin sections an4 magnetic samples were prepared fron the cores•, a spimer magnetometer was built and used to determine the direction of remannt magnetization, of 'the cores, several of the cores wer partly demagnetized to check their magnetic stability, and the, vertical magnetic anomaly recorded over the dike analyzed. The results f the investigation indicate the following: 1. The dir eCtios of magnetization of the samples ar fairly cons istnt, with mean declination of 1340, inclination of 86 degrees, with a four degree radius of conidenc.e at the 95 percent level. This corresponds to a noxth magnetic pole position of 530 N., 95°W. 2. The intensity of magnetization varies greatly between adjacent samples, even betweert sampl.e.s from the same. core. The intensity is less than the average rear the .suth contact o the dike and. near the center. The- average intensity of magnetization is 4. 35 x 103c g. s emu/cc 3. 60-cycle a. c. partial demagitetization at a peak field of 500 oesteds slightly increases t1 intensity of mnagnetization of samples fro•m near the contact, but reduces the intens ity of the interior samples to about one half oE. their initial value. The 4gher perentages of chlorite and deute.ric hornbiende near the contact indicate late stage oxidation reactions which may have produced a magnetic tonstituent of high coercive force. The percentage of magnetite is the same near the contact as near te oenter of the dike. 4 As theY demagnetizing field strength is irtcreased the directions ot rnagnetization of the- çors converge. After demagnetization at a peak 60- ytte field of 500 'oersted-s, the inean inclinatIon of the samples is -82° and the mean �3 declination is 55°, with a four degree radius at the 95 per" cent confidence level. The results of demagnetization are based upon the data from four s ampies. 5. The difficulties encountered in the intrpretation of the anomaly over the covington dike indicate that care nwt be taken in terpreting vertical field anomaijes over bodies with revere ed remanent magnetization by us e of formulas such as Cook's (1950) which are based on the assumption that there are no anomalous polarization effects present. �4 THE WATER PROBLEMS OF THE MINING INDUSTRY OF THE UPE R PENINSULA OF MICHIGAN J. H Butler The irreversible trend to-ai-d etr action of lcw er-'grade metallic mineral deposits, as localized, high-grade deposits become depleted t13ruh incre acing oneurnption, involves large-s cal&, highly me.chanized mining and mineral processing operations. Such operations normally have very high energy and water requiremet. Year by years the availability of vtater for mineral industries becomes of greater signfficace as growing 7cr:uiation -nd intensification of ecwmIc activity throughout the nation bring about competition for existing water resources Despite the very favvrable hydologic environment of Mihigans Upper PennsuIa, water "probi.em&' appear to be developing 'th respect to the mini and processing of low-grade .ron ore deposits on the Marquette Iron ange. The situation t one plant is éamined and water availability for future regional desrolopment of the Marquette Iron Range is considred. Implications are drawn far the future ot low-grade mineral ecploitation in the subhumid areas of the country. �PETROLOGY OF APRECAMBRIANPLUTON NEARPEMBINE, WISCONSIN A. Cain rock units have been mapped within some 350 square miles of the Precambrian grariiti and metamorphic complex ci northeastern Wiscorisin. The r1ative age-relationships among these units are suggested, primarily from a study of enoliths, as follows: Nine Youngest: Diabase dikes Amberg Granite Newingham Granodiorite }Ioskin Lake Granite Metagabro sills TwIe Foot Fall Quartz Diorite Marinette Quartz Diorite Bitite gneiss Oldest: Quinnesec Formation Structural, modal, and specific gravity data are presented for the Newingham Granodierite to illustrate their behavior within, this terrane. The results of structural analysis are somewhat inconclusive but suggest a ioughly coicentric foliation pattern for the 40 square mile pluton. Data derived from 5 spcimens of Newingham Granodiorite are used tc illustrate the geographic variabilit {br means of trend surface analysis) of quartz percentage, feldspar percentage feldspar ratio potash feldspar/ plagioc1ase) color index, and specific gravity within the mass. Correation coefficie4ts are given for each of the 10 pairs of variates t indicate degrees of assQciation. From thi quantitative analysis, feldspar ratio is Seen to be the one variate which does not conform to "expected" patterns of behavior. �6 APPLICATIONS OF THE HIGH SPEED DIGITAL COMPUTER TO GRAVITY AND MAGNETIC ANALYSIS R. L. Coons and Peter Wolfe Niflety prcent of the time spent in geophysical interpretation is taken up by manipnlating numbers leaving only about ten percent of the time for geologic interpretation of the results. Until the advent of the high speed digital cnputer certain analysis techniques were. t costly or time consuming to perform by hand. The proper applications of computer tecb iques to data reduction and analysis allow the geophysicist to reverse th above procedure spending ten percent of his time on arithmetic and ninety percent of his time on interpretation. Pgrams eoped to date in magnetic and gravity analysis clearly demonatrate sorn of the advantages in using the computer. Magnetic readings •can be electronically recorded on paper tape, fed into a coxnpixter, corrected for drift and. diurnal ariations, and plots of total intensity, second derivatives, and downward continuation, made by the computer.. This eliminates all erors that are normally introduced in recopying nd manipulating the data by hand. The resulting maps o the analysis can be pibtted and in certain cases even contoured by the computer. Gravity readings are cirift corrected by hand along with the s1ireyers notes.. These operatiotis could be. pefo:rmed by the computer but this gives the interpreter a chance to examine the reliability of the data. The computer then calculates the Bouguer Anomalies using several density asumptions, plots profiles, checks før errors, performs least square surface analysis, and plots the residual maps. SeraI types of resdil analysis are thus quickly obtained leaving more time for geologic Interpretation of the results. �7 DIAGENETIC REPLACEMENT IN ORE OF THE EMPIRE MINE OF NORTHERN MICHIGAN AND ITS EFFECT ON METALLURGICAL CONCENTRATION Tsu-Ming Han This paper describes the texture, mineralogical, and chemical criteria of diagenetic enrichment of the low grade irpn-forxation at the new Empire Mine near Palmer, Michigan, and the influence of the diagenetic changes upon nietallurgical response of the ctude ore to benefication. At the Empire Mine, in Section 19, 47-26, the iron-formation is involved in a secondary fold of the. Marquette syclinorium. The strike changes from N-S at the north side of the section to E-W in the southern oart of the section. Dips also change from W to NW to N as the formation swings around the fold. In general the dips average about 300. On the basis of mineral ratio, and mineral assemblage, the iron-formation may be classified into five lithological types: (a) interbedded complex (which includes magnetite -bearing g reywacke, magnetite -hematitic che rt with clastics, and the other four lithological types), (b) magnetite-carbonateche rt, (c) magnetite-silicate - chert-carbonate, (d) magnetite-chertcarbonate, and (e) magnetite -bearing chert- carbonate. Laboratory data revealed that the iron content among the abovementioned nonclastic rocks is fairly uniform averaging 32% in type (c) to 36% in type (c). The ma.gnetite content varies considerably averaging 20% in type (e) to more than 42% in type (b). The iron uni.t recovery averages 44% in type (e) to 88% in type (b). Such variations are, in a large part, attributed to the differential diagenetic enrichment of rn-agnetite in the different lithological types. The following criteria, involving the formation of the mineral magnetite, support the contention that diagenesis has played an important role in the geologic history of the Empire ore: (a) more or less the same mineral assemblage but different mineral ratios; (b) more than one generation of magnetite; (c) cut-off and replacement of carbonate-chert by magnetite larnina; (d) evenly distributed magnetite; and (e) lack of correlation of metallurgical concentration results between samples from the same lithologic horizons. �8 MAGNETIC INVESTIGATIONS IN IOWA D. H. Hase In 1961, vertical intensity magnetic measurements were made in evera1 areas for the Iowa Geological Survey as the initial phase of a project to map the etitir state magnetically. Ground and airborned magnetometer su.veys of the state are currently in progress. The magnetic anomalies are attributed to changes in the lithológy and/or configuration of the Precambrian cyrstaUine basement rocks. The Vincennes anomally is probably due to a body of feldspathized gneiss r diorite which is a few square miles in extent, has a maximum relief of a few hundred feet, and is about 2900 feet below the surface, The Manson anomaly is attributed to somewhat feldspath.ized, znagnetiterich, biotite and augen gneiss. Relief owing to erosion and perhaps partly to faulting in the vicinity of the main anomaly may be of the order of 1000 to 1500 feet along a northeast-trending buried ridge. Large gravity and magnetic anomalies in the Adair area are apparently related to rather shallow, basic igneous rocks. Departures from the smoothed profiles define the Thurman-Redfield and other basement structural ZOne8. A magnetic high without a corresponding gravity high near Greenfield is attributed to ferruginous schists in the base.rnent rocks, - �9 OPTIMUM DIP NEEDLE READING METHOD Wm. J. Hinze A good deal of the confusion surrounding the use arid interpretation of ip needle observation originates from the method by which the instrument s read. The selectjon of the.optimum reading method is dependent on four criteria: accuracy, reliability, simplicity, and rapidity. These are all important; however, their relative importance varIes dependIng or.the requirement and conditions of the survey. Various reading methods are va1uated with respect to these criteria with the aide of a laboratory investigation employing controlled magnetic fields. The optimum readIng method varieS, with the survey, but the reading method based on the arithmetic mean of the second, twice the third, and the fourth reversals of the oscillating dip needle is most universally acceptable. �10 A REGIONAL MAGNETIC MAP OF THE SOUTHERN PENINSULA OF MICHIGAN Wm, J. Hinze A regional vertical magnetic intensity map is presented of the Southern pninsula of Michigan. It is based on a peninsulawide ground magnetic survey with observations made on a six mile interval plus detailed observations in local areas. This map which primarily reflects lithological and structural variations in the Precambrian basement rocks and their depth beneath the surface shows a strong relationship to the trend of sedimentary structures of the Michigan basin and Precambrian trends of Wisconsin and the Northern Peninsula extrapolated into the basin. The magnetic map and the regional gravity map also show a marked resemblance in many areas. In particular the Michigan Gravity High correlates with a major positive magnetic anomaly. �11 EXTENSION OF THE NORMAL DISTRIBUTION TO FITRING OF TWO DIMENSIONAL (SURFACE) GRAVITY AND MAGNETIC DATA W. W. Johnson amd S. A. Finnegan The normal distribution curve has been successfully used in filtering one dimensional (profile) data. This method has been extended to two dimensional measurements of potential fields, both as a smoothing function and as a high-pass filter. The method involves the use of weights determined by different processes operating on a normal curve of revolution. of this method are shown applied to remove regional trends gravity anomalies yielded by a buried spherical body and a buried Results from infinite vertical sheet. �12 r _____ PRELIMINARY INVESTIGATIONS OF LATE WISCONSIN DRIFT NORTH OF LAKE SUPERIOR .T. W. Page and D. R. Lindsay Problems of late Wisconsin chronology have been studied for the past fl years in the Lake Superior region of Minnesota and adjacent States. Work of a similar nature has been carried Qut on the Canadian side of the Lake but has been local and disconnected. Investigations of a regional nature and correlation of new findings with presently known data will help to complete the Canadian picture and pO5Sibly aid in solving some of the admitted problems remaining on the American side. As aioffshoot of work presently in progress and supported by the Geological Survey of Canada, some new data and correlations are presented. The Rainey lobe of Patrician ice is believed to have developed at least two systems within the area discussed after retreat from the Ver' million moraine in Minnesota. They are believed to be post Two Creeks in age. Retreat to and beyond the Hartman-Kaiashk moraine allowed development of Lake Johnson in the Steeprock area and a similar lake in the Wabigoon basin. Outlets to both lakes were blocked by ice to the west during their early history. '—morainal The Nipigon and Dog Lake moraines are both considered younger than the Hartman-Kaiashk moraine and may represent the positions of an ice front during the life of Lake Duluth. While definite conclusions cannot be drawn at present it appears that a large area in northeastern Minnesota was free of ice from Two Creeks time n and was closely followed by disappearance of the ice from adjoining areas in Ontario. A study of plant geography lends further credance to this hypothesis. retreat After of the ice from the Nipigon moraine a later front developed some 30 miles east of Lake Nipigon and trended in a southeaster- ly direction to the White River area. The presence of extensive outwash plains and varved clays east of Lake Nipigon suggest a greatly expanded and possible connection with Lake Ojibway. forerunner of this lake Final retreatof the ice over the continental divide impounded the stages of Lake Ojibway which at this time drained through the Pic early �13 -vr system to the Lake Superior basin. Lake Agassiz II has yet been dtermined. No definite eastern outlet for throughout the area await continuThis and more complete detail of vnt5 vestigat10. �14 GEOPHYSICAL EVIDENCE FOR THE PRESENCE OF KEWEENAWAN VOLCANICS IN THE AREA OF UPPER. MICHIGAN BET WEEN MARQUETTE AND SAULT ST MARIE R. W. Paten.aude During five days in August, 1961, 1100 data miles were flown with an Elsec proton precession magnetometer in the area of Paleozoic sediments between Marquette and Sault Ste. Marie. The magnetic data suggests that the area between Grand Island and Sault Ste. Marie is undr1ain by Keweenawan type volcanics. The magnetic pattern is believed to reflect the influence of therrno- remanent magnetization in the volcanics. �15 GEOPHYSICAL INVESTIGATION OF A DIABASE DIKE NEAR LTANSE, MICHIGAN R. J. Reuss The purpose of the investigation was to determine the relative age of the reversely magnetized, fresh dabase dikes that occur in the area near L'Anse, Michigan. The dike investigated trended from an area of late Huronian slates into an area overlain by red sandstones of Cambrian or late Precambrian age. A magnetometer survey was run across the dike at several places in an attempt to determine whether or not the dike penetrated the sandstone, or was overlain by it. The results of the survey seem to indicate that the dike is overlain by the sandstone, and is therefore of an earlier geological age. �16 GEOCHEMICAL AND GEOPHYSICAL PROSPECTING FOR COPPER, LEAD, AND ZINC IN THE EAST GLARE AREA OF IRELAND RichardW. Schultz The rocks in this area are predominantly lower Carbonilerous limesstoneS and si-tales, underlain by Upper Devonian shales and sandstones. The najor structural feature is a large, shallow, south westerly trending syndilne. The nearest exposure of post-Carboriiferous intrusive rocks lies over one hundred miles from this area. On the north limb of the syndlirie, in an area containing numerous minor folds, re several small base metal suiphide deposits which had been mined in the last century. A small, but geologically significant chalcopyrite replacement deposit has been discovered recently by means of the induced polarization method. The two basic typcs of suiphide deposits found in the area arc: (1) fracture-filling calcite-suiphide lodes with minor walirock replacernrt in competent limestone, and (2) replacement deposits in shaly limestone controlled by upfolded irnpernneable barrier rocks. High pH of stream and ground water throughout the area inhibits the of heavy metals and renders them practically immbile. For that rason, as well as poor drainage conditions in general, stream water and sediment sampling was found to be ineffective. Also, blind deposits could not be expected to have secondary chemical dispersion haloes associated with them. However, glacial erosion has caused strong and clearly discerni ble physical dispersion of metals from subouteropping deposits and, therefore, a method of reconnaissance soil sampling was adopted to search specifically for glacial dispersion patterns. Experimental work showed solubility that all of the known deposits could have been found by geochemical float tr?cing, and several new anomalies have been discqvered. variable-frequency induced polarization method was used in and detailed geophysical prospecting. It was found to be effective in detecting even relatively small amounts of disseminated suiphides and, therefore, to be more sensitive than other electrical methods. Its main disadvantage is poor resolution and geometric definition of anomalies, making The reconnaissance it difficult to spot drill holes. The vertical-coil electromagnetic technique was found to be unsatismost reconnaissance work as it does not respond well to dis- factory for �r 17 :inatd suiphide rruineralization. Howeier, ii has been effective in disrfl1flg flat-lyingblack shale beds coiitaining primary pyrite which give riSe CO strong induced polarization anomalies. Self-potential measurements provided an additional means of recognizing the troublesome pyritic shale. �18 M\GNETITE ANALYSIS BY MAGNETIC SUSCEPTIBILITY P. D. Shandley A transistorized magnetic susceptibility meter which utilizes the balanced transformer principle is described. The instrument has been used to determine the percent magnetite in ores. The results of this• method of analysis are comparable to the results obtained by magnetic separation and cheniical analysis. �19 IRON ORES OF BIHAR AND ORISSA, INDIA A. K, Sneigrove While visiting the University of Sind, Hyderabad, West Pakistan, in 1961-62, as Fuibright Lecturer in Geology, the speaker made a brief tour of the Tata Iron and steel empire of Northeast India. The Iron Ore Series, containing an estimated 8 billion tons of good grade wrkable ore in Bihar and Orissa produced 6,670,000 in 1960. Rocks of the Iron Ore Series range from shales and quartzites to coarsegrained clastics and are associated with pyroclastics, only slightly metamorphosed. The well layered major deposits occur chiefly along ridges. Generally soft, friable and powdered varieties together form the major part of a deposit, and hard, compact varieties are found mostly in the top portions. Depths are about 300 feet. Properties of varieties generally available in one- deposit are hard 33%, soft 16%, lateritic 9%, biscuity or flaky friable 33%, blude dust 10%. Principal minerals are hematite, magnetite, rnartite, and occasionally also lirnonite and goethite, together with some hydrous iron silicates such as greenlite and chamosite. Quality, origin structure, alterations, and development planning, treatment, and economics will also be discussed.. The author is indebted to Tata Iron and Steel Corpor3tion for much information and many courtesies.. �r•__ 20 THE USE OF PRECIPITATION CHROMATOGRAPHY IN GEOCHW CAL PROSPECTING J. D. Spain The use of agar gel columns containing arnmonium sulfide precipitant for mineral identifications and trace element determination will be described. (Spain1 J. D.., AnaL Chern. 32; 1622-1624 (1960), Spain, J. D.,, Ludernan, F. L., and Sneigrove, A. K.,, Econ. Geology, in press). Sensitivity studies showed cobalt, zinc, lead, bismuth, antimony, and to be determined in solutions containing 20 ppm or less. Iron, cadmium, copp'r, and arsenic were determined in solutions containing less than 300 ppm. All analyses involved the standard amrnonium sulfide column with the metal irons applied in 6 M HC1 søluton. In preliminary studies to determine accuracy of qualitative identification, 80 synthetic unknowns composed of tin, three component mixtures of the previously mentioned ions were analysed. iron, lead, cadmium. and cobalt were identified correctly in all unknowns. arsenic. antimony1 and tin gave any extensive difficulty, these having been determiiied with less than 80% accuracy. Only Sixty one mineral samples were analysed by this method and the results were compared with those obtained from the emission spectrograph. It was found that the major metallic constituents of miner als can be det erznined with a high degree of accuracy. How in most cases the minor con- stituents were missed. It'was concluded thatin special cases the method would be a useful field tool. The more recently developed technique of filter paper precipitation chromatography will be described and its advantages over the agar gel technique will be discussed. These advantages include. stability..bf:the precipitation media, speed of chrornatograrn development, quantitative as well as qualitative results in a permanent form, and inexpensive, portable apparatus. �2.] GEOLOGICAL SURVEY, PIKES PEAK AREA, BARAGA COUNTY, MICHIGAN. Kiril Spiroff Unusually high geiger counter readings were detected in outcrops on the west side of Huron Bay, ten miles east of L'Anse, in Barag& County, Michigan. The area was investigated by trenching and diamond drilling. Surface mapping and ir1ormation from three diamond drill holes yields the following geological column (from top to bottom): andstone, iron formationu, quartzite, conglomerate, and granite. The study fills a gap in our knowledge of the Precambrian area of Michigan's Upper Peninsula. It did not reveal any deposits of economic sigrificance. �22 FPOTWI4LL MNERALIZATION I THE OSGEOLA AMYGDALOID MICHIGAN NATIVE COPPER DISTRICT R. J. Weege and A. W. Schillinger Conventional underground mapping methods and diamond drilling are being applied in a study to determine the nature of the copper ore occurrences r.car the footwall of the Osceola amygdaloid. A description is given of the character of the airiygdaloid and the types and location of native physical copper mineralization and associated alteration. Work to date suggests that the footwail ore is formed independently from the hanging-wall ore and tha.t localization at the footwall is caused by impermeable barriers. The barrier concept as advanced by earlier writers to explain the concentration of solutions in the ore body as a whole is carried one step further and is found to be equally as applica!ble for the localization of smaller oreshoots within the Osceola ore body. �________ r 23 CURRENT GEOLOGICAL RESEARCH IN THE PALMER AREA, MARQUETTE DISTRICT, MICHIGAN J. Zinn r Palmer area is structuraUy a distinct syncline containing jirnikean rocks and is separated from the main Marquette synclinorium by the prominent Volunteer Fault. Exposures of the Negaunee iron formation in this area show variations not characteristic of this formation s seen elsewhere. The lower horizons at the Negaunee contain various proportions of clastic debris and some lenses of conglomerate material. 1dso, this fôrrriation rests on Ajibic quartzite locally without the normally intervening Siamo slate. Currently, these sedimentational problems are being investigated by Robert Henny. The investigation to date appears to show that the Negaunee was a near shore deposit in this area, that the chert layers in the formation rapidly solidified into durable beds and that the iron precipitated in trivalent condition. iron forination was deposited continuously with the clastics even in the conglomerate horizons. The implications of .ch deposition encourage speculation as to rate of deposition an. other sedimentary problems concerned with Lake Superior type formations. The Several other problems in the Palmer area deserve attention. Some of these are the extent and nature of the Volunteer Fault, the Eastern limits of the Palmer syricline and the pyroclastics in the iron formation. It is understood that research on some of these problems is being done at the University of Wisconsin. � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1962 Description An account of the resource Institute on Lake Superior Geology. Michigan College of Mining & Technology, Houghton, Michigan. May 10-12, 1962 Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1962 Contributor An entity responsible for making contributions to the resource L.O. Bacon C.G. Bufe J.H. Butler J.A. Cain R.L. Coons S.A. Finnegan Tsu-Ming Han D.H. Hase W.J. Hinze W.W. Johnson D.R. Lindsay T.W. Page R.W. Patenaude R.J. Reuss A. Schillinger R.W. Schultz P.D. Shandley A.K. Snelgrove J.D. Spain K. Spiroff R. Weege Peter Wolfe Justin Zinn Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/7d87a2792037d451dbf6e8c0ff55ab06.pdf c174ae149f6d8beb5546748ab48f1a3a PDF Text Text Field Trip "Stratigraphy of the.Biwabik Iron Formation 11 Sponsored by the Lake Superior Geology Club Duluth, Minnesota May 4, 1965 �,, ~~ G>,._ /<I AUBURN ~t-«~ 1-/19 19/11. G' . G'-'9 ~ )'1- ~ 0 '9</ ~ O,s- +-~ ~ -v~ ~,o -v~~ <? INDEX MAP OF THE MESABI DISTRICT , MINNESOTA �FOREWORD Gentle reader, take heed, the field trip which you are about to take - not a polished affair with textbook illustrations and trip leaders able to J ve glib expla.ne.tions for everything you are going to see. o the gene al objectives for which the Lake Superior Geology In keeping with stitute was or- g nized, that is, to present preliminary r e sults of investigation in new areas of geologic interest, the leaders of this trip plan t o show you their approach tp subdivic1:1.ng the Biwabik iron formation beyond the basic fourfold subdivision ~rst proposed by J. F. Wolff in 1917. That the problem of further subdivision i ls difficult can be accepted si nce such authoritie s as Gruner, Grout and Broderick, E te , Schwartz and Gunderson have all come up with systems that many individuals use but which do not appear to be generally acceptable to all 'rorkers in the ield. In such a situation we may expect considerable discussion and disagreement i th any system proposed. ~Y emerge, Perhaps in the anticipated clash of opinions the truth. but don't count on i t. In any event the trip should be instructive " o both you and the leaders, and perhaps even entertaining to the philosophers rong you contemplati ng the state Of geol ogic knO'£o7ledge concerning this 1 the ,randfather of all iron for-mations. . A secondary but highly interesting part of this trip \d.ll be the 1ppo1~unity to observe the changes vmich take place in unoxidized iron formation rom the Eveleth area eastward almost to the contact of the Duluth Gabbro. T~~s spect of the trip should be of particular interest to students of metamorphism and those less c,o ncerned with the local problems of iron formation stratigraphy. lble controversy exists even in this area, the individualists among you vTontt I q.ave to accept any of our leaders' statements since the rocks themselves \-Till be tvailable for identification and collection. Due to the unexpectedly large number of people participating in this trip, we are antici pating some difficulty in maintaining our schedule of arrivals and departures f rom each stop. ~orn blows . compensation. Please return to the buses promptly a fter the I f you are left i n the pit don •t panic, apply for unempl oyment �The field trip will start at 7: 50 A.M. at Hotel Duluth and proceed rectly to the Auburn Mine property outside of Virginia . Upon completion of tq.e one stop at Auburn , the buses ldll ta.k.e us to the Erie property and proceed through four stops in various parts of the pit. Two stops are planned in the I REf Serve property to complete the program for the day. The buses will return to Duluth via Aurora and deposit passengers at the beginning point. Passengers 'rushing to remain on the Range should make private arrangements for transportation ftam the Reserve property or possibly from Aurora. It is anticipated that we ,dll finish the trip around 6:00 P.M. Lunch ~dll be served at the third stop in the Erie pit and rest stops are planned on ent ering the Erie property and leaving the Reserve property. Please read, consider and observe the regulations on the following page to which ~rJ have agreed in order that we can gain entrance to the various properties. �ruiruuTIONS: Through t he courtesy of the Oliver Iron Mining Division, United States Steel Corporation , Pickands Mather & Co., and the Reserve Mining Company, we have beFn granted permission to enter, inspect and collect small specimens on their rebpective properties. t~ In return for this privilege, we have agreed to abide by following regtuations which apply not only to visitors but also to all company pe~sonnel. l. pits. Safety hats and goggles will be worn at all times while in the various You will be issued such equipment at the first stop. This equipment is charged out to the Lake Superior Geology Club and we will have to pay for it if it is not returned at the end of the trip . 2. Picture taking of equipment is discouraged in all active pits and all pictures forbidden on the Reserve property. at the entrance to the Reserve property. for the fun of it . Arrangements will be made to check cameras Please do not try t o outwit these regulations You may make it difficult for future geologists to enter these interesting areas . 3. Please use caution when approaching rock walls . The talus slopes are notoriously unstable footing and rock slides from the walls above are not uncommon in the spring. While the purists among you will want to remove specimens from the living rock, let us remind you that \dth taconite, it ' s going to take a lot of hammering. We have a long, tO'\.lgh day ahead of us, so save your strength. also applies to potential mountain goats climbing up rock faces. Thi s You may endanger yorrself and other people as well as delay the trip , so stay off high faces. 4. Please use discretion wnen hammering on rocks near other people . Taconite is tough and hard. at high speed. Sharp chips have a tendency to fly in all directions The safety goggles supplied you are not just a bureaucratic detail. Us~ them at all times and make your arm on Minnesota taconite. sure they are on people near you before you t est It is reported to have an average crushing stkength of 55,000 pounds per square inch . �Ea ster n Biwabi k Str atigraphy f rom Gunderson a nd Schwartz .Minnes ota Geological Survey Bulletin 43 -~ z;~a ~ ~~ !I ~~! ;- s ~ -'C-Q; ~ ..~ ~ GENERALIZED COLUMNAR SECTION OF THE BIWABIK IRON-FORMATION ~ ~ -~ ~ ~ £ r: ~-:! == j -!!cri ~ ~ ? ! -0f:i!..._ou E~ ~ r ~ s o ~ ~ -- J: j IN THE EASTERN MESABI DISTRIC T, MINNESOTA i? 1-- - -- - - --------=---,--.,-,--- - - - -- - - - - - - - - l 6 i ·~· ~:g 32: c.5 Descnption of Submembe rs ;; .:...: w - Q (Notations cO - Jf ~ J I B {!6) (eo~t} and (we!:> I) refer to orcas near the easter n and western drill holes) calcite marble,. minor diop side, wollastonite , id oc ro s e, andradit e and quartz j """-;;;;ered (di'op/;ide) chert taconite locally wilh hornblende, hedenberq ite and some cummingtonite a nd oc tmol•te /ami'n aled (ferrohyperslhene - moqnel i le) c;uarl.t ! aconite with hedcnberqite c >~ w (l_ (l_ ::J taconite {west) I /:::,vy laminated (oclinoh'le-moqnefite) chert taconite 1-:---:-::::--fV ··-·tonile ond minor hedenbc rgi te -' (/) cr laminated (cummin91onite - mognetite) chert and loyoli te (east) and (421 "' .D :> <I 0 (71 E 161 F (201 with abundant granule struc tures and locolly w ith quart zfilled seplorio s tructures; m inor magneti te, c ufT'ming tonite and o ttinolite shaly bedded (cumminqtonite-maqnetite) quartz laconile hedenocrgite (cost); locally abundant w•l h minor andradite cumminglanite (west} quartz taconite (ea st) and mol/led (andradite) quartz obundonl magne ltl e - bearing granules throughout G (251 wavy layered (actinolite? -maqnetite) quartz taconite f---:1 J wit~ cumminc;~- quartz taconite r----t--__ond H locally liOl local ly with foyoli te (eas t) taconite (west) with with minor hedenberq:itei and cummingtonite (wes t) .,--+ - - (Sl (l6 ) " ' alq~l (moqnetile) quorlz toconife with abundant magnetite- r ich granules ond "---: ebblcs; conglomcrolic fabric throuc;~houl; minor hematite r---+-_ granule (maqneltle) quartz facomle with obundonl magneti te - rich pebbles ~top and thic kly layered (magnel!le) quoriL tocomle near bottom >- K (351 L (301 near wavy layered (silicole moqnelite) quartz taconite with abundant moQne tite· rich granules ond ptbblcs ; silicates ore actinolite ond ferrahyperslh ene (east) ond cummingtamte (we st) 9 1- cr w I u wavy layered (st'licote-magnett~e) silicate-quartz taconite with abundant mag netite-rich granules ncar bollom; silic.o tes with magnetite ore ferrohypersthcne and hor nblende (e o:o t) and cumming toni te and actinoli te (wes t); silicates wi th quartz ore fcrrohypers thene (cost) ond c umminqtonite (west) cr w (l_ (l_ ::J layered (maqnelt~e) loyolite-quorlz /acon/tc with fcrrohypersthene layered (maqnel/te) cumminqtom~e-quar tz tacom~e (wes t) M (201 N 41 0 (17) foyalde -quartz tacomle tocomle (westli minor with ferrohyp ersthene (eosl) and {eas t) and cumminqlomle-quorlz mac;~ne t ite bedded granule (magnetite) quortz - loyolile tacomle with some fcrrohypers thene and minor cummingtoniti! (cost) to quartz -cumminqtom~e focamle with · moogranules (west} ~et ite -beoring r: sholy quortz- foyoli!e tocomle cumminqlontle taconite 10 foyoltle tocomle (easJI and sholy quorlz- to cummingtont~e tocom~e (west); minor moonetite '!!aceous grophite -sikcote-quortz laconlle with abundant ferrohypersthene and minor foyolite, biotite, olmondilc ond pyrrhotite (eosl) and traces of pyrite, pyrhotit e and cummingtonite (wes t) . layered (magnetJ/e) loyolite -quortz taconite with m inor cumminQtonite ered (moqneflle) quorl.l taconite with minor cummingtonite throuq:hout, and hedenbcrgitc and some l oj!alite (east) ljr;;nule (magnetite) quartz taconite 1---+---+-- --flj r-minor f-,---:-:-:-i(/ (;;ered and granule 'j -, locotly, with minor cummingtonite throuqhout, ond foyolitc least) (moqnetJ~e) cummingtom~e-quorlz taconite with hedenberqite ond some fayolite (cos t) ~rlz f-;-;---;-o;;-( FIGU!\1': 5. - taconite with minor hedenbcrgite and cummingtonitei clastic quartz p ebble zone locally at bose Generalized columnar section or the Biwabik iron-[ormation. };j �sw - sw 28-58 - 1 7 S E -S W 1 7-58-17 ·. N W - NW 20-58 - 1 7 .r. - I . I 1/ v ~I , - ------ -- - ---- ---/+-- ---- / / : I I SW-N W ) 20 - 58-1 7 I I S E - NW 2 0-58 - 1 7 I G E O LOG I C M AP OF AUBU R N M I NE N SC ALE } . 1" - ·4 00' a. 0 --+--· ---- ~----· -·-· -·t--· --+--1 I I I l_ __ L E GE ND GEOLOGIC C O N TA CT S ( A PPRcJX I MA T F) ~ O VE R DU R OEN ____ ...,. CRE ST OF BA NK ..- ___ _... T OE O F B ANK �STRATIGRAPHIC S~UENCE IN THE BIWABIK IRON FORMATION AUBURN mNE 'lhickness in feet 1 UJ PER CHERTY MEMBER 16. 2 Jaspery, conglomeratic and algal chert (G and 15 . 14 13. 12 . + 10. submember I) 10 (est . ) Covered interval 10 (est.) Nodular hematitic chert beds interbedded with laminated hematite-silicate- magnetite beds 48 +'l Laminated hematite- silicate-magnetite beds with subordinate jaspery chert beds and lenses 31 Jaspery, conglomeratic chert beds interbedded with subordinate laminated hematite-silicate~magnetite beds 28 Cherty taconite ld th thin irregular ma.gneti te beds, magnetite mottles and disseminated magnetite 16 143 SIM'Y MEMBER ll. s 3 Laminated silicate magnetite tacom. t e with subordinate silicate chert lenses Laminated non- magnetic silicate taconite, fissile in part. 6 ' of fissile "intermediate slate" at bottom (G and S submember Q) lOl 37 ---:l::-:38=- LOWER CHERTY MEMBER I 9. Cherty taconite with irregular magnet ite beds . Upper 10 ' dark·~ colored silicate rich beds instead of magnetite beds , making base of lower slaty somewhat indefinite . 37 Mottled silicate- magnetite chert with chert "pebbles" and abundant coarse granules. ll Cherty taconite with thick (l"!) magnetite beds and mottles 84 has 8. 7 6. 5. Mottled cherty taconite vlith thin, very irregular magnetite ~ds. u Thick jaspery chert beds interbedded w1 th varying proportions of thin, regular laminated magnetite-hematite- silicatecarbonate beds . 66 �l Thickness in f'eetl CIIER1'I' MEMBER (Cont'd) 4. Thick hematitic chert beds with subordinate la.minated zones. Some clastic sand grains near bottom. Much carbonate. 8 Jaspery, conglomeratic and algal chert w1 th subordinate laminated zones. Sand grains common. 4 2. Massive chloritic (or hematitic) sandstone 8 1. Jaspery, conglomeratic and algal chert 4 3. 236 Total thickness exposed mGAMA ,.. QUARTZITJt~ 517 Base not exposed 1. Units 15 and 16 measured on bank between truck road and railroad near entrance to pit. Units l - 5 measured on SW bank, at SE end of' pit. Remainder measured above railroacl. 2. Unit numbers correspond to numbers pa.inted on the walls of' the Auburn Mine and are not intended to be a new stratigraphic system. 3. The lower slaty-upper cherty contact is not well-marked and disagreement exists as to its position. �__..... ...--- ERIE MINING CO MPANY / MAP OF ? PLANT AND PIT / / / I AREAS LEGEND I COARSE CRUSHER 2 FINE CRUSHER ,3~ CONCENTRATOR 1)PELLET PLANT , §\LOADING POCKET • 6 STOCKPILE 7' GENERAL SHOPS ' ,\ WEST PIT BIWABIK IRON FORMATION VIRGINIA FORMATION ::," 1;- 1 {! { DULUTH GABBRO �STOPS AT ERIE PITS Stor. At this stop, we have the base of the iron formation in the West Pit. The gama quartzite and the basal algal layer and conglomerate can be found in the roa • The alternating chert and argillaceous layers of submember V are exposed in the outer op. ' Fok The bank at the south edge of the pit is the Lower Slaty material P&Q. The r efore, the widt h of the pit here is the entire Lower Cherty member. 1 Sto J 2. This stop shows the upper part of the Lower Cherty ore horizon. The submember R can be seen along the top of the bank. It is greenish in color and !contains much minnesotaite and greenalite. Iead D irectly below this is the wavy bedded submember R. This is more noti ~ eable toward t he west, (containing abundant granular jasper). J The mottled submember S is below this layer. This submember occupies most of the lower part of the bank. It also contains much jasper as well as the con J. picuous pink to red carbonate mottles. J StoR 3. At the east end of the cut, we find the even bedded (U) and the alternating ma~sive and slaty submember (V). The massive layers consist almost entirely of ryedium grained green silicates . Some granular jasper and flinty black chert occ j rs. Minor amounts of sulfides are present. I Proceeding westward, we encounter the lower wavy bedded submember (T) and the mottled submember (S). Here the mottles consist of fine grained sili ~ ates instead of the carbonates seen in Stop 2. StoJ 4, This stop is in the upper part of the Lower Cherty member and shows submembers R & S . It correlates with Stop 2. The effects of the gabbro to the sou~heast are quite apparent. At the extreme east end there are abundant sulfides and Jvery coarse grained dark green silicates. Proceeding westward along the cut the grain size decreases and buff colored silicates (ferrocummingtonite) begin to app~ ar. The cut immediately to the south is in the Lower Slaty horizon (P). This :::t~::::u~ ;~~: ::~::::h::8 :les:;here Sto~ and shows recrystallization. Small 5. At this stop, units 0 through K can be observed. Representative blocks of e t ch subunit are marked. Locally abundant coarse grained silicates and some sulftdes occur. A few blocks show portions of jet-pierced holes. Some septaria are !e vident. �STJ ATIGRAPHY OF THE BIWABIK IRON FORMATION AT THE ERIE MINING CO. Pr oda~l:n~eo:::~ation ,.. A. Calcite - marble layer. B. Lean quartz and silicate as irregular zones and layers. U:PP+r c. s..a t y (3 - 16) (10- 35) & D. Laminated zones of magnetite and silicate interlayered with thinner chert layers. (30 - 50) E. Massive granular chert with disseminated magnetite and occasional magnetite-silicate layers. Septaria. (5 - 10) F. Similar to C. & D. but the chert contains much disseminated magnetite and granular jasper. (25 - 35) G. Massive with much disseminated granular magnetite and jasper. Locally concentrated into irregular granular layering. Conspicuous carbonate or silicate mottles. (15 - 20) H. Similar to above except more abundant granular layering. Layering becomes more laminated toward bottom. ( 10) I. Algal structures and conglomerates. J. Granular. Similar to G. & H. but more abundant disseminated granular magnetite. Carbonate - silicate mottles are very con• spicuous. (5 - 15) ;..!, h (3 - 10) Upple r K. Cherty Thin, irregular and discontinuous magnetite layers having distinct boundaries separated by thicker massive layers of lean chertsilicate. The diabase sill is within this unit. (28 - 48) L. Moderately thick layers of laminated magnetite and silicate separated by equally thick layers of chert with much disseminated magnetite. ( 30 - 40) M. Thin, well defined magnetite layers similar to K. with more magnetite occurring as granular layers and disseminated magnetite (20 - 45) N. Not recognized. o. Alt ernating laminated magnetite - silicate zones and chert layers. Similar to L., but with increasing disseminated granular magnetite in the chert toward the bottom. Conglomerate near base • ( 15 - 3 5) 'l �-2- Pilobable Correlation to Gunderson L~er P. Massive granular silicate unit with vague layering. (75 - 90) Sl/a ty Q. Black, moderately laminated argillite. R. Upper unit is massive with granular silicates in a chert • silicate matrix. Lower unit is similar to above with scattered tnirt layers of magnetite and disseminated granules. (20 - 35) s. Irregular zones and mottles of dense and granular magnetite. Much disseminated magnetite in the massive chert. Abundant carbonate or silicate mottles. (15 - 35) L wer Ta Cherty I . u~ v. (5-45) = L lern?ed, st/1!- Thin irregular layers and granular concentrations of magnetite within thicker massive chert layers. Occasional mottles. (20 - 35) Magnetite occurs in even bedded iaminated zones wfth s~lica~e and argillite and/ or as even bedded concentrations of granules iri the chert. (15 - 30) Thick laminated zones of hematite, magnetite, silicate and argillite alternating with massive granular chert layers. Conglomerate, algal and/ or slate usually occur at the base of this member. (6 - 30) �RESER 'E ' B BABBRlY~ A MONHESOTA LAKE SUPER UOR PNST i'V'Uli'E Of EOLOGY fiElD fRIP MAY 4B ~923 NERAt.: RESER VE MiNING COMPAN~ ~OLUCY DOES NOV PERMIT POSSEIIION OF CAMERAS ON VHE OPERVYa Oft PLEAS£ CHECK YOUR CAMERA WITH PLANT PROTECTION AV VHE MAIN GAV Eo i: PLEASE AVOID SVANDtNG 'tOO CLOSE UNKS ON VOP OF VHE WALL~ 0 YHE NOR'ti'H AND SOUTH WALL o MAKE CLOSE INSPECTION OF THE WALLS ll..ARGt VACON II 'II'[ UN ADDI T ION NAZAROOU~o AYO»O CLRMB ING ON VHE MUC PILES AS THE RE IS A POSSIBILITY or DtSLODGING CHUNKS VACON VV'Eo APPROXIMATELY 85 FEET OF ijpp R CHERTY AND 35 THE BAlE OF VHE NORTH WALL VO THE VOP OF THE YHE ~LWTH GABBRO LSE EN LY VHUS REGUON ABOWV 3 OUVH WALLo TH A FEW ~~NORED FEET TO VHE $0UVH UN VH t EXHUBtV~ EPRE~ENVr O FEEV OF ijpPER St.ATY ARE STRATA AREA o GENER£L L ~ CoN E- A HIGHER DEGREE OF METAMORPHISM THAN STOP No o 2 WH i CH MULE$ VO VHE WE~To ~GNEVITE AND QUARTZ ARE VKE PREDOMI NANT MU NERALSo H DEN8ERGtTE 1 FAYAL ITE, ACV tNOLIVE, FE RROHYPERSV HoWEVER, COARSE GRA U N~ Of NE AND HORNBLE NDE ARE COMMON c UNT BLACK HiSINGERI TE CAN 8E SEE N IN YH£ NORTH WAL lo IT tS ONE OF THE LAST StLICA~ E Tp FORM IN V~E BIWABIK HRON f ORMATION AND CUVI THROUGH ALL PREVIOUS MINERAL ASSEMBLAGE o ~NOERSEN AND SCHWARTZ AVVRUBUVE VHE roRMAVtON ~ OtNBERGIVE 8 FERROHYP£RSVHEN£~ ~EGMAYHTE WEINSo EiSENV4AllY OEFLY ~r Ywo COM~OSED CF HORNBLENDE AND CU VYPES OF VEI NS ARE Q~ARVZ AND ~UNK or MEDIUM fO COARSE GRA INED M~NavONI E~UOENV I TO fHE IN VHtl AREAo ALKAL I FELDSPAR o tNJEC~tON OF THE AC IDIC VE INS fHE MAFIC VEINS CON IIV HORNBlENDEo 2: W[ ARE ABOUV NORVHEA~V 3 WALLo Ml E VO fHE WE@V OF SVO~ Noo ~e A MONOCL WNAL FOLD II VID NV IN �I ~rD NERALLY FINER GRAt MAGNET IV~ SI ZE II PREVALENT I N THIS AREA Q MN ADDITION vo QUARVZ CUMMINGVONRTE, ACVINOLUTE AND ANDRADIVE ARE COMMON MONERALSo OTHER F A URES VO NOTE IN VHOS AREA ARE THE £LG L ZONE &NO A SMALL DIABA E DUKE I ~ICH TRENDS SE-NWo ,,6oo FEET A LARGER DIABASE DIKE ABOUT 35 FE WtD£ OCCURS APPROXIMATELY W SV AL ONG THE PIT CENTER LINE FROM fHE EA T END 'LSO VRENDI SE-NWo or VHE PITo TH~S DIKE � https://digitalcollections.lakeheadu.ca/files/original/535d7f6dfe72cecce1a31043297745d9.pdf 469cd2492591ee36bab1d297d7b4d2d0 PDF Text Text �NINTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY University of Minnesota, Duluth May 2-3, 1963 PROGRAM Thursday Morning - May 2, 1963 Science Auditorium, University of Minnesota, Duluth 9:00 General Meeting of the Institute ............ Chairman, H. Lepp Secretary, D. H. Hase SESSION I Co—chairmen: J. C. Green, J. S. Owens 9:30 D. W. Pollock S. C. Nordeng: PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA Co., MICH. 9:55 George Moerlein: STRUCTURE AND STRATIGRAPHY OF THE KEWEENAWAN IN NORTHWESTERN MICHIGAN 10:20 lO:+5 11:10 BURIED EXTENSION OF THE KEWEENAWAN Isidore Zeitz & P. K. Sims: BASIN IN MINNESOTA - A GEOPHYSICAL STUDY P. K. Sims & Isidore Zeitz: GEOLOGIC INTERPRETATION OF AERO— MAGNETIC ANOMALIES OVER PRE-KEWEENAWAN ROCKS IN CENTRAL MINNESOTA THE APPLICATION OF S. C. Nordeng, C. 0. Ensign & M. E. Volin: TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT GENERAL DISCUSSION 11:35 12:00 LUNCH — MAIN BALLROOM, KIRBY STUDENT CENTER SESSION II Co-Chairmen: F. D. Effinger, T. E. Stephenson STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX IN THE 2:00 W. C. Phinney: 2:25 C. N. Hanson, W. C. Phinney & P. W. Gast: THE THERMAL EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, MINNESOTA �* Hf 2:50 THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND DIKES AW SILLS NEAR HOVLAND, MINNESOTA N. W. Jones: COFFEE BREAK 3:15 3:145 :1O G. FORMATION, THE STRATIGRAPHY AND STRUCTURE OF THE ROVE B. Morey: GUNFLINT LAKE AREA, MINNESOTA STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION, CARLTON AND PINE COUNTIES, MINNESOTA Paul Wieblen: GENERAL DISCUSSION 14:35 6:30 THEL/ DINNER - MAIN BALLROOM, KIRBY STUDENT CENTER Dr. R. L. Heller, Director, Earth Science Project; Head, Department of Geology, University of Minnesota, Duluth Speaker: EARTH SCIENCE AND THE SECONDARY SCHOOL CURRICULUM Topic: Friday Morning, May 3, 1963 SESSION III Co-Chairmen: C. Tychsen, I. L. Reid P. R. E. Hessevick: REFINEMENT OF THE 9:00 R. L. Blake, T. Z. Zoltai 9:25 G. L. Laberge: CARBONATE MINERALS IN THE IRON FORMATION AND THEIR SIGNIFICANCE 9:50 R. E. Randolph: SUSCEPTIBILITY MEASUREMENTS CF EMPIRE MINE MAGNETIC MATERIAL & HEMATITE CRYSTAL STRUCTURE COFFEE BREAK 10:15 Hoppin, J. C. Palmquist & L. 0. Williams: CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE ON THE LOCATION OF THE TENSLEEP - BEAVER CREEK FAULT, BIGHORN MOUNTAINS, WYOMING 10:145 R. A. 11:10 C. M. Gallick: CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA 11:35 M. A. Rogers: BIOGEOCHEMISTRY OF MINNESOTA LAKES: 12:00 LUNCH - MAIN BALLROOM, KIRBY STUDENT CENTER CARBOHYDRATES �SESSION IV R. W. Marsden Chairman: 2:00 J. H. Zumberge & 14. R. Farrand: LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY ORIENTED LAKES IN NORTHERN ALASKA 2:25 C. E. Carson: 25O 0. M. 'hwartz: 3:15 THE SUBDIVISIONS OF THE BTWABT}( FORNATTON ON THE EASTERN MESABI GENERAL DISCUSSION Saturday, May , 7:30 - Hotel 1963 Duluth FIELD TRIP TO THE MESABI IRON RANGE Field trip leaders: F. D. Effinger, Pickands Mather & Company J. 14. EmanuelsOfl, Reserve Mining Company C. L. Iverson, Oliver Iron Mining Division Richard Strong, Oliver Iron Mining Division �1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology REFINEMENT OF THE HEMATITE CRYSTAL STRUCTURE R. L. Blake.Y, T. Z. Zo1taiY, and R. E. Hessevick!" The crystal structure of hematite has been refined as an initial phase of studies involving atomic positions and vacancies in hematite during reduction to magnetite. Three—dimensiofll diffraction intenItieD were collected and automated on a spherical single crystal of hematite with both manual Buerger single crystal diffractometer. The structure has been refined with R factor of 7.1 pera least squares program and the final structure gave an cent. The structure model of Pauling and Hendricks has been confirmed with essentially no change in the iron coordinates and approximately a 5 percent change in the oxygen coordinates. The interatomic distances and bond angles were also calculated. TMinneapolis Metallurgy Research Center, Bureau of Mines 2! Department of Geology g Geophysics, University of Minnesota �2 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology ORIENTED LAKES IN NORTHERN ALASKA C. E. Carson University of Minnesota, Duluth Study of numerous thaw-lakes in the permafrost of the Arctic Coastal Plain has revealed that basin shape and orientation is controlled by winddriven waves and currents with associated thermal effects. The lakes range in size from mere puddles to basins 8 or 9 miles long, and all possess a similar basin morphology. This morphology consists of wide sub-littoral shelves and bars on the east and west sides, with the deeper central basin extending uninterrupted to the north and south ends. The ba- sins are elongated in a north-south direction, and have length-width ratios ranging from 1 to 5.1. Few basins are over 8 feet deep. In the Point Barrow area, most basins taper toward the north. Analysis of wind data from the Barrow weather station has revealed that summer winds are bimodal, being either easterly or westerly, average some 15 m.p.h., and are remarkably steady from one direction for several days at a time. orientation. Their average directions are nearly perpendicular to the axes of Investigation has shown that wind-driven wave action on the east and west sides, and the presence of circulation cells in the north and south ends, has produced the characteristic basin morphology; therefore, orientation. �3 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA Cyril M. Gallick University of Minnesota, Minneapolis The Middle Ordovician Decorah Shale is exposed sporadically in a 20-. mile wide band, extending from St. Paul to the southwestern corner of Houston It is a green-gray or less commonly a blue-gray shale that contains County. thin (generally 0.1 to 0.2 foot) interbeds and lenses of limestone and co- quina. The limestone layers are widely separated in the basal 10 to 20 feet, but increase in number irregularly upwards. In the middle of the formation, there are two or more zones, 3 to 5 feet thick, which contain limestone beds separated by less than O.i feet of shale; near the top, the limestone beds A few of the uppermost beds are become thicker and more widely separated. The formation is 89 feet thick at St. Paul and thins one to two feet thick. progressively to 25 feet at the Minnesota-Iowa border. The minerals in the grade size less than 1/512 mm were determined with "illite" (a 10 layered silicate with inter— the X—ray diffactometer to be: layers of a lL mineral), kaolinite, orthoclase, and calcite. Where all minerals are present, peak intensities indicate that orthoclase and illite predominate. The material sized greater than 1/512 mm is mostly fossil hash and At St. Paul, illite and orthoclase are present throughrare quartz grains. out the formation, apparently in constant proportions; kaolinite and calcite are sparse in the basal part but occur in significant amounts in the middle and upper part of the section. At Rochester, the basal shale contains illite or-thoclase, and calcite in proportions similar to that in the upper part of the St. Paul section and sparse kaolinite; the middle shales consist entirely of illite; beds in the upper part contain either kaolinite or orthoclase or both, but apparently only in minor amounts. The orthoclase in the Decorah Shale has been presumed to be the result of authigenesis. All illite (001) peaks on the diffractometer from the St. Paul section and from the basal part of the Rochester section are very asymmetrical, extending from 9.BA to slightly more than lLR, possibly indicating a considerIn the middle and able amount of interlayer 1L4X mineral in the structure. upper parts of the Rochester section, the illite (001) peaks are nearly symmetrical. analysis of a shale which had been weathered for possibly more This peak than five years showed only a change of the illite (001) peak. much more asympeak, broader and was lower in relation to the (002) illite X-ray metrical than that of any other shale analyzed. little more than l7R. It extended from 9.8k to a �L. UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on May 2-3, 1963 Lake Superior Geology THE THERMAL METAMORPHIC EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE G. N. Hanson, W. C. Phinney, and P. W. Gast University of Minnesota, Minneapolis, Minnesota The effect of the thermal metamorphism of the 1.0 billion-year Duluth Gabbro on the 2.5 billion-year Snowbank Granite can be seen in the changes of the Rb-Sr ages of the biotites and the changes in the degree of triclinof the potassium feldspar in the granite. tion zones parallel the granite-gabbro contact. icity In both cases, the transi- Biotites from the granite within 2.0 kilometers of the contact (map distance) have Rb-Sr ages of less than 1.2 billion years. At distances greater than 2.0 kilometers, the successive biotite ages increase regularly to 2.55 billion years. The change in the ages exhibited by the biotite is shown to result from the loss of radiogenic strontium from the biotite strucThe mechanism for this loss is assumed to be either recrystallization ture. of the biotite structure or volunie diffusion of the radiogenic strontium out By a trial and error process of fitting theoretical of the structure. curves to the data, an activation energy of about 50 kilocalories for recrystallization by a zero—order rate process and an activation energy of 85 kilocalories for volume diffusion are proposed. Potassium feldspars at distances greater than 2.0 kilometers from the contact are maximum mirocline (maximum triclinicity) as determined by mea— Within 2.0 kilometers surement of the 131-131 spacing by x-ray diffraction. of the contact, the potassium feldspars are primarily orthoclase (monoclinic feldspar) except for several samples near the contact which show mixed orthoclase and microcline. The albite content of the potassium feldspar tends to be only a function of the facies of the stock and ranges from 0r59—0r96. The above data raise several questions which as yet are unanswered: (1) Why is microcline the potassium feldspar at distances greater than 2.0 kilometers? Could this be explained by regional metamorphism of the stock during the Algoman orogeny about 2.5 billion years ago? (2) Why did the potassium feldspar within 2.0 kilometers of the contact change to orthoclase upon thermal metamorphism by the gabbro and then not revert back to microcline upon cooling? Could this be a result of a lowering of water pressure in the stock at the time of the intrusion of the gabbro? �5 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE OF THE LOCATION OF WYOMING THE TENSLEEP-BEAVER CREEK FAULT, BIGHORN MOUNTAINS, Richard A. Hoppin - University of Iowa, Iowa City, Iowa John C. Palniquist - Monmouth College, Monmouth, Illinois Lyman 0. Williams - The California Company, Pensacola, Florida angic fdnlt, The Tensleep—Beaver Creek Fault (Laramide in age) is a high The north side 32 miles in length, trending E-W across the Bighorn Mountains. The fault has moved up a maximum of 1350' in the axial portion of the range. presently known is a major transcurrent fracture but is the only such feature this trend, has that crosses the whole range. Why the fault formed and has the eastern 12 miles been a puzzle. This investigation was restricted to The Precambrian rocks were exalong which the Precambrian rocks are exposed. might have been reamined to see if there was any structural anisotropy that sponsible for the localization of the fault. One is best developed near the and dips 500 This foliation varies from N.80°E. to N.80°W. in strike fault. Several zones of pervasive foliation up to 300 feet wide were mapto 70°N. is less well deAs one goes north away from the fault, the foliation ped. in width are preveloped although local zones of a few inches to five feet shear surfaces; In the field, the foliation looks like closely spaced sent. for occahowever, thin sections indicate complete recrystallization except Later, pegmatitic masses cut this sional deformed relict plagioclase augen. In the fault zone, these foliated rocks, and the sedimentary foliation. quartz cementation are rocks, are brecciated and crushed. Quartz veins and 50 feet wide. characteristic. The crushed zone is only about Two strong foliations were discovered. This The second foliation trends N.50°-65°W. and dips 60° to 70°NE. foliation is dominant to the north of the fault but is absent near the fault. This fabthe fault. It is also the main foliation in the Horn area south of plagioric is also completely recrystallized with only a few relict deformed mylonitizatiofl arid quartz veining have clases. Later, zones of crushing, straight A particularly strong cataclastic zone is followed by a this trend. This same zone conportion of the valley of the North Fork of Powder River. is probably responsible for a small detinues southeast into the fault and flection of the fault. It seems reasonable, therefore, that the Tensleep-Beaver Creek fault was formed along an E-W zone of pervasive foliation and deflected in one area along another zone of northwesterly foliation. These foliations were formed under deep-seated conditions of plastic deformation followed by reLaramide took place at crystallization. The later deformation during the shallow depth and was of a brittle nature. �6 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND THE DIKES AND SILLS NEAR HOVLAND, MINNESOTA Norris W. Jones University of Minnesota, Minneapolis, Minnesota It is tentatively concluded from onissan'e go1ogic inepping in the vicinity of Hovland, Cook County, that the Duluth gabbro complex does not exand othtend as far eastward as Lake Superior, as suggested earlier by Grout ers (1959). Instead, the gabbro appears to terminate at the Brule River. The mafic rocks along the shore that previously were called Duluth gabbro are the lower part of the Hovland diabase sill. Three other diabase or gabbro units are recognized in the area. Petrographic and x-ray studies show systematic changes in the Hoviand sill. Silica, alkalis, and iron gradually increa3e upward from the base. is present As in the Skaergaard intrusion of East Greenland, an olivine gap and the two pyroxene boundary is crossed. The compositional changes are in- ferred to indicate that the sill formed by crystal fractionation. The relations of the intrusive units in the area can be explained as the result of emplacement of Logan intrusives, followed by intrusion of the Duluth gabbro ccinplex. The Logan intrusives were emplaced along a dominant- ly northeast—trending fracture system, whereas the Duluth gabbro complex in this area strikes essentially east-west. The Hoviand area represents the intersection of these two malor structural trends. �7 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute May 2-3, 1963 on Lake Superior Geology CARBONATE MINERALS IN THE IRON-FORMATION AND THEIR SIGNIFICANCE Gene L LaBerge University of Wisconsin, Madison, Wisconsin To allow more rapid identification, a staining technique was used in studying the carbonate minerals in the iron-formation. The procedure is outlined in an to simp- article by Warne in the Jour, of Sed. lifying the identification of the carbonate species, the stain showed beauti- Pet., March, 1962. In addition fully the relationship of the various carbonates to one another, and the association of particular carbonate species with certain other minerals. Some generalizations to which there certainly are many exceptions which may be made, are as follows: Most of the siderite is primary material. The ex- tremely fine-grained carbonate which comprises up to 75 per cent of some slaty layers in the iron-formation is almost certainly primary. ial is siderite and/or very iron-rich ankerite. This mater- Textures indicate that the siderite granules, which are not uncommon, are probably primary. Unques- tionably, secondary siderite is not common. In contrast, most of the ankerite, ferroandolomite, and dary. dolomite are secon- Much of this secondary carbonate is probably a byproduct of the de- composition of the iron-rich ankerite to form magnetite, with which it is usually associated. However, primary ankeritic carbonate in both the slaty material and in granules does occur. �8 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology STRUCTURE AND STRATIGRAPHY OF THE UPPER KEWEENAWAN ROCKS IN NORTHWESTERN WISCONSIN George Moerlein Bear Creek Mining Company, Anchorage, Alaska Between the summer of 1955 and the winter of 1960, Bear Creek Mining Company explored the western tip of the Lake Superior Syncline in quest of possible copper-bearing Nonesuch formation. The area covered includes por- tions of Ashland, Bayfield, Douglas, Washburn, and Burnett Counties, Wisconsin. Field mapping, extensive magnetic and gravity surveys, some refraction seismic work, and diamond drilling each played a part in outlining the geology of the area. The normal sequence of Keweenawan sediments, Copper Harbour, Nonesuch, and Freda formations was recognized, and the tratigraphy of each formation will be discussed. The structure of the area is essentially that shown on the 1948 edition of the Geologic Map of Wisconsin, a northeast plunging syncline. however, is locally complicated by faults of major Evidence importance. will be presented which indicates that the formation of the Lake Superior Syncline, at least in Wisconsin, began in an time. This, very late Keweenaw- �9 UNIVERSITY OF MINNESOTA, DULUTH of Geology Department May 2-3, 1963 Institute on Lake Superior Geology THE STRATIGRAPHY AND STRUCTURE OF THE ROVE FORMATION, GUNFLINT LAKE AREA, MINNESOTA G. B. Morey University of Minnesota, Minneapolis, Minnesota in the South Lake Quadrang1. near Gunf lint Lake in Cook County, was completed in 1962. The area is on the north limb of the Lake Superior structural basin; accordingly, the strata Geologic mapping of Animikie Group rocks strike eastward and dip consistently five to 15 degrees south, except adjacent to the Duluth Complex where the dips increase to as much as 65 degrees. The Rove Formation overlies the Gunflint Iron Formation, apparently conformably, and is truncated by the Duluth Complex; approximately 1,800 feet of The formation consists of two recognizable lithologic units. Rove are exposed. The lower unit, about 400 feet thick, consists mainly of a black, very finegrained, thin-bedded or fissile argillite with abundant graphitic or carbonaceous material and pyrrhotite, interbedded with lesser amounts of gray, mediumThe grained, massive graywacke. Calcareous concretions are locally abundant. argillites, grayupper unit, about 1,400 feet thick, consists of interbedded wackes, and quartzites; the latter two rock types become more abundant upward in the section. Graded bedding, sole marks, intraforrnational argillite fragments, convolute and small-scale cross-laminations and clastic dikes suggest a subaqueous flow origin for much of the upper unit. A south-southwestward movement of material is suggested by many of these structures. The Animikie Group rocks contain several east-trending sill-like bodies, mainly of diabasic gabbro, which range from less than 100 to more than The sedimentary rocks adjacent to the sills are 1,000 feet in thickness. metamorphosed to mineral assemblages. characteristic of the horr1blende-hornfels facies. The sills are correlated with the Logan Intrusives; they are older than and are truncated by the Duluth Complex. �10 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 THE APPLICATION OF TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT S. C. Nordeng1, C. 0. Ensign, Jr.2, M. E. Volin3 Over one hundred sets of drill hole data were taken from the files of the White Pine Company and coded on IBM cards. The section was divided into upper and lower halves and linear, quadratic and cubic surfaces of best fit were computed for each half for average copper percentage, thickness, and ounces of silver per ton, utilizing a taped multiple regression program on a medium speed digital computer. The linear surface for the upper half accounted for one-half or better of the departures from the mean and showed slight improvement for higher order surfaces, suggesting that the trends of the quantities under consideration are essentially planar in nature. The best fit was found for copper, The surfaces show an increase in thickness to the the poorest for silver. north and northeast, and in copper content to the southeast. The lower section showed macimum improvement in the sum of squares for the cubic model for both percent copper and thickness. Maps of the cubic surfaces successfully predict the location of a known ore body for which Departures of observed values from com no data was entered in the program. puted values for the lower half are interpreted as resulting from relative thickening and thinning of the upper part of the lower section which is relatively barren, and the lower part of the lower section in which most of the ore is found. 1 Department of Geology and Geological Engineering, Michigan College of Mining and Technology, Houghton, Michigan. 2 Chief Geologist, Copper Range Company, White Pine, Michigan Institute of Mineral Research, Michigan College of Mining and Technology, Houghton, Michigan �U UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX, GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, LAKE COUNTY, MINNESOTA William C. Phinney University of Minnesota, Minneapolis, Minnesota Mapping and petrologic studies of the Duluth gabbro complex in the Gabbro Lake and Greenwood Lake quadrangles during the summers of 1961 and 1962 have indicated a complex series of gabbroic intrusions associated with antiform and basin-like structures. A major intrusion in the southeast quarter of the Gabbro Lake quadrangle and the north-central part of the Greenwood Lake quadrangle is roughly elliptical in plan, has a long axis of at least nine miles, and is inferred to be cone-shaped. It intrudes anorthositic gabbro and concentric layers that dip nearly vertical at the border and nearly horizontal at the center. Regular variation in mineral assemblages from olivine rich at the border to pyroxene-rich at the center indicate a normal differenNumerous smaller gabbroic intrusions as well as zones of tiation sequence. intrusions have been mapped. has Olivine gabbro with well defined layers having graded olivine concentrations in rhythmic succession forms a broad, shallow basin in the southwest quarter of the Gabbro Lake quadrangle. Within the basin, there are many anorthosite lenses that contain numerous one- to two—inch patches of olivine, apThe eastern boundary of parently concentrated from the interstitial fluid. the basin is in sharp contact (apparently intrusive) with the anorthositic The relative ages gabbro intruded by the cone-like intrusive mentioned above. of the cone-like gãbbro intrusion and basin-shaped gabbro intrusion are not known. Southeast of Gãbbro Lake, a marker zone in the gabbro can be traced around an antiformal structure that is elongated subparallel to the basal contact of the gabbro and has an anorthositic gabbro core. In the same area, a very coarse-grained pyroxene- and ilmenite-magnetite-rich dike, that is as much as one-fourth mile wide, can be traced for several miles. �12 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA COUNTY, MICHIGAN D. W. Pollock and S. C. Nordeng Michigan College of Mining and Technology, Houghton, Michigan During the summer of 1962, the writers initiated a study of a portion Some results of the "Northern Complex" which lies in Baraga County, Michigan. of this study are reported herein. (1) amphiboSeveral lithologic groups have been mapped. These are: plagioclase—rich gneis— lite; (2) greenstone; (3) rnesocratic gneisses and (4) varieties. ses. Each of these groups can be subdivided into more specific The groups occur in definite belts and the following gradations were observed in the field: greenstone chiorite-plagioclase gneiss amphibolite mesocratic gneiss plagioclase-rich gneisses A thin "infolded" belt of Michigamme (?) phyllite has been located west of Clear Lake in Sec. 14, R 49 N, R 32 W. The broad structural trend is an arc, convex to the west. In detail, the structure is more complex. Poles to foliation (llsdiagrams) were plotted, but with poor results. The most useful approach was to outline the structure on the basis of vertical foliation trends. The origin of the foliation reMesoscopic linemains in doubt as the origin of the rocks is not yet known. ation is only feebly developed. Investigation is continuing. of some of the many problems raised during this study �13 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 SUSCEPTIBILITY MEASUREMENTS OF EMPIRE MINE MAGNETIC MATERIAL E. Richard Randolph Cleveland Cliffs Iron Company, Ishpeming, Michigan The Negaunee Iron-Formation at the Empire Mine on the Marquette Range in Michigan consists, briefly, of magnetic cherty iron-formation, magnetic cherty carbonate iron-formation, magnetic cherty silicate iron-formation and a hanging wall member containing many large clastic facies interbedded with the precipitate iron—formation. The common criterion for grading ore at the mine is on the basis of per cent weight recovery. The ore type which presents the greatest problem in grade control is the clastic facies of the iron-formation which can vary It is very difficult to distinguish in weight recovery from 10% to tl1%. macroscopic means. Close orrich, moderate and poor der magnetometer surveying is an aid to localizing large zones, but a more definitive procedure is desirable for day-to-day control. It was suggested that susceptibility measurements on the cuttings from blast hole drilling might indicate the grade of the ore in that hole more cheaply and reliably than crude Fe analyses or streamlined Davis tube testing. clastic ore material by Susceptibility is the ratio of the intensity of magnetization acquired by a substance to the strength of the magnetizing field acting on the In a rock containing magnetite as the principal magnetizable constitbody. uent, susceptibility is, for practical purposes, the measure of the amount of magnetite present. Because per cent weight recovery of magnetite is the criterion for the cut-off s between rock, lean ore and ore in the hanging wall clastic zone, a program relating susceptibility measurements to per cent weight recovery was started. The conclusions are as predicted: measurements show a broad range of values for the general area but within a limited area correlate sufficiently well to offer a rapid, cheap, reliable method for sampling blast hole cuttings for grade control. �l&1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology BIOGEOCHEMISTRY OF MINNESOTA LAKES: CARBOHYDRATES M. A. Rogers University of Minnesota, Minneapolis Fossil carbohydrates have been found in trypical sedimentary rocks; carbonaceous organic rocks such as peat, coal and lignite; fossilized wood; insect remains; modern lake sediments; modern and ancient marine sediments; and in lake waters. Carbohydrate materials were studied in the aquatic plants, lake waters and lake sediments of two eutrophic-alkalitrOphiC lakes of central Minnesota. Both free sedimentary sugars and sugars liberated on hydrolysis were recovered. Glucose, galactose, xylose and arabinose are the dominant sugars in order of decreasing abundance in aquatic plants of the two lakes. Maxima and minima in these sugars, as well as in the content of cellulose and hemicellulose, show little relation to season of collection and appear to be characteristic of individual plant species. Acid hydrolysis of lake bottom sediments recovered the eight sugars, arabinose, xylose, galactose, glucuronic acid, glucose, rhamnose, mannose and ribose, in concentrations ranging from 19.1 to 0.1 mg/gm of dry wt. sedThe variety and amount of these sugars is believed to demonstrate iment. the importance of microorganisms in altering the carbohydrate fraction prior to stabilization and preservation within the sediment. Acid hydrolysis of lake sediments from a deep core from Blue Lake, Minnesota, recovered in order of decreasing abundance the eight sugars, xylose, glucose, arabinose, galactose, mannose, rhamnose, ribose and glucuronic acid. A natural stability series for carbohydrates in the lacustrine envifairly stable: xylose, glucose, rhamnose, arabinose; moderateronment is: galactose; very unstable: ribose, mannose; fairly unstable: ly stable: glucoronic acid. �15 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 GEOLOGIC INTERPRETATION OF AEROMAGNETIC ANOMALIES OVER PRE- KEWEENAWAN ROCKS IN CENTRAL MINNESOTA P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Isidore Zietz, U. S. Geological Survey, Washington, D. C. in An aeroinagnetic survey completed by the U. S. Geological Survey of 1961 has clarified our knowledge of the Pre-Keweenawan rocks in an area about 3,000 square miles in central Minnesota, extending from the latitude in of Little Falls, in Morrison County, south to the vicinity of Gaylord, of the anomalies In the northern part of the area, sources Sibley County. units have have been identified from scattered outcrops and separate rock been extended, based on geologic considerations and magnetic data. The aeromagnetic data indicate that the igneous rocks of the Penokean orogeny (Woyski, 19L19), which have been quarried extensively for building monumental stone in a broad area centered at St. Cloud, extend in the and eastward beneath oversubsurface south at least to latitude L5°l5' N. Northwestward from St. Cloud, lapping upper Keweenawan sedimentary rocks. and schist appears to be the dominant bedrock. In the southern part of the area, outcrops are lacking and interpretation of the magnetic patterns is more equivocal. Except for an anomaly at above igneous rocks of Lake Washington in Meeker County, which probably is mafic composition, interpretation of the magnetic anomalies intermediate or of the baseis not attempted. South of Hutchinson, a change in the trendmarked discontiby the magnetic pattern, suggests a ment rock, as indicated nuity, possibly a fault or an unconformity, in the Pre-Keweenawan rocks at this latitude. �16 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geo1gy May 2-3, 1963 STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION CARLTON AND PINE COUNTIES, MINNESOTA Paul Weiblen University of Minnesota, Minneapolis, Minnesota Calcareous concretions in the Thomson Formation found in the vicinity of Carlton are of two types. The concretions in graywacke and graywacke—iate beds consist of massive calcite, are ellipsoidal, and lack a distinctive internal Those in structure other than bedding, which conforms to the enclosing rock. finer-grained slate beds are zoned; they contain an inner core of slaty mater— ial, surrounded by well—crystallized calcite or by quartz with sutured grain The outer zone has a pseudo cone-in-cone structure, defined by boundaries. bands of slaty material. The calcite in both types of concretions replaces quartz and feldspar. The zoned concretions on the limbs of folds in the slate and graywacke succession are rotated out of the plane of bedding. The c axis of the calcite in the pseudo cone-in-cone structures is oriented parallel to the direction of maximum compression and a cleavage, which is well developed, parallels shear These features afford a promising means for further study of directions. structural relations in the formation. Remnants of concretions are found in the more intensely metamorphosed phases of the Thomson Formation southwest of Carlton, in phyllite, metagraywacke, and mica schist. Quartz has replaced the calcite in phyllite. Well—zoned concretions occur in the metagraywacke. The outer zones of these consist principally of hornblende, garnet, quartz, and andesine; the cores contain mainly epidote, quartz and andesine. Sections of the cores show that they are deformed into boudins. They also contain characteristic S-shaped structures formed by shearing and defined by heavy mineral concentrations. These similarStructures similar to these occur in the slate and phyllite. the concretions can be ities indicate that further sampling may show that Formation. used as stratigraphic marker beds in the Thomson Remnant calcite is found in the concretions in the mica schist, metagraywacke and phyllite. The (211) spacing of the calcite ranges from 3.04 angstrorns in the slate to 3.02 angstroms in the schists, indicating the occurrence of relatively pure calcite (less than 5 percent Fe,Mg) throughout the entire formation. Plagioclase coexisting with calcite ranges from An5 in the slate and graywacke to An40 in the mica scist and metagraywacke. It has been found that radiographs afford a practical method for studying the internal structures of the concretions. Fluorescence excited by electron bombardment provides a mean of distinguishing calcite from dolomite. �17 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology BURIED EXTENSION OF THE KEWEENAWAN BASIN IN MINNESOTA GEOPHYSICAL STUDY A Isidore Zietz, U. S. Geological Survey, Washington, D.C. P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Approximately 30,000 linear traverse miles have been flown eromagnet— ically by the U. S. Geological Survey across the "mid—continent gravity high". This is, perhaps, the most oustanding gravity feature in the United States, extending from near Lake Superior in a southwesterly direction to the Sauna basin in Kansas. Coupled with the gravity measurements and meager drill hole records, the aeromagnetic data strongly, if not unequivocally, imply the existence of a several-mile-thick accumulation of Keweenawan lava flows, extending uninterruptedly for 800 miles, f tanked by Pre-Cambrian sandstones which locally may be more than a mile thick. Total thicknesses of lava flows and neighboring sandstone can be estimated from the gravity data, whereas the aeromagnetic data supply the details of the configuration of the upper surface of the flows. In Minnesota, the magnetic data clearly outline the Twin Cities artesian basin, an elliptical trough 60 miles long in a northeast direction and 30 to 35 miles wide. basin and north of latitude LL°35' N., At the eastern margin of the the magnetic data suggest that the basin is bounded by a narrow northeast-trending horst of mafic volcanic rocks, probably elevated at least 1,000 feet above the adjacent rocks. The horst is the basement manifestation of the Fiudson-Afton anticline, a northeast-trending Paleozoic fold. In southern Minnesota, south of latitude L44°l5' N., the mafic lavas are at considerable depths, but the surface of the flows rises to within 1,500 feet at the Iowa border. �18 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY James H. Zumberge and William R. Farrand University of Michigan and Columbia University to Cores were recovered from eleven drill holes in water depths of 500 drilling 1,130 feet in Lake Superior in 1961 and 1962. A shipboard, rotary and to lorig was used to penetrate the unconsolidated Pleistocene sediments The sediments were recovered by gravity and piston cate the bedrock surface. coring -- continuously in the upper 30 feet and intermittently below that depth. reaching bedThe longest core penetrated 686 feet of sediments without sediments rock, and it shows at least four alternations of glaciolacuStrifle The other cores penetrated only 7 to 156 feet and the varved), red lacustypical sequence was gray, lacustrine clay (lower part trifle clay (some varved), and red clay till. Below the till, well—washed and red, clayey till. red and sand (outwash?) was found in three holes, and in four other holes white (Cambrian?) sandstone was reached. drill A sub-bottom depth recorder was used in combination with the topography. Near logs for the interpretation of stratigraphy and sub-bottom broad bedrock valthe Minnesota coast, more than 700 feet of drift lies in a valleyIn the eastern part of the basin, strong north-south trending ley. modified stream and-ridge topography appears to be a submerged, glacially system, rather thinly covered with glacial drift. Also, the possibility of strong east—west faults between Keweenaw Peninsula and Sault Ste. Marie is indicated. � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1963 Description An account of the resource Institute on Lake Superior Geology. University of Minnestota, Duluth, Minnesota, May 2-3, 1963 Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1963 Contributor An entity responsible for making contributions to the resource R.L. Blake T.Z. Zoltai R.E. Hessevick C.E. Carson Cyrill M. Gallick G.N. Hanson P.W. Gast Richard A. Hoppin John C. Palmquist Lyman O. Williams Norris W. Jones Gene L. LaBerge George Moerlein G.B. Morey S.C. Nordeng C.O. Ensign M.E. Volin William C. Phinney D.W. Pollock E. Richard Randolph M.A. Rogers P.K. Sims Isidore Zietz Paul Weiblen James H. Zumberge William R. Farrand Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/7338fb743a085a3636f695617419003d.pdf 469cd2492591ee36bab1d297d7b4d2d0 PDF Text Text �NINTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY University of Minnesota, Duluth May 2-3, 1963 PROGRAM Thursday Morning - May 2, 1963 Science Auditorium, University of Minnesota, Duluth 9:00 General Meeting of the Institute ............ Chairman, H. Lepp Secretary, D. H. Hase SESSION I Co—chairmen: J. C. Green, J. S. Owens 9:30 D. W. Pollock S. C. Nordeng: PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA Co., MICH. 9:55 George Moerlein: STRUCTURE AND STRATIGRAPHY OF THE KEWEENAWAN IN NORTHWESTERN MICHIGAN 10:20 lO:+5 11:10 BURIED EXTENSION OF THE KEWEENAWAN Isidore Zeitz & P. K. Sims: BASIN IN MINNESOTA - A GEOPHYSICAL STUDY P. K. Sims & Isidore Zeitz: GEOLOGIC INTERPRETATION OF AERO— MAGNETIC ANOMALIES OVER PRE-KEWEENAWAN ROCKS IN CENTRAL MINNESOTA THE APPLICATION OF S. C. Nordeng, C. 0. Ensign & M. E. Volin: TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT GENERAL DISCUSSION 11:35 12:00 LUNCH — MAIN BALLROOM, KIRBY STUDENT CENTER SESSION II Co-Chairmen: F. D. Effinger, T. E. Stephenson STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX IN THE 2:00 W. C. Phinney: 2:25 C. N. Hanson, W. C. Phinney & P. W. Gast: THE THERMAL EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, MINNESOTA �* Hf 2:50 THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND DIKES AW SILLS NEAR HOVLAND, MINNESOTA N. W. Jones: COFFEE BREAK 3:15 3:145 :1O G. FORMATION, THE STRATIGRAPHY AND STRUCTURE OF THE ROVE B. Morey: GUNFLINT LAKE AREA, MINNESOTA STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION, CARLTON AND PINE COUNTIES, MINNESOTA Paul Wieblen: GENERAL DISCUSSION 14:35 6:30 THEL/ DINNER - MAIN BALLROOM, KIRBY STUDENT CENTER Dr. R. L. Heller, Director, Earth Science Project; Head, Department of Geology, University of Minnesota, Duluth Speaker: EARTH SCIENCE AND THE SECONDARY SCHOOL CURRICULUM Topic: Friday Morning, May 3, 1963 SESSION III Co-Chairmen: C. Tychsen, I. L. Reid P. R. E. Hessevick: REFINEMENT OF THE 9:00 R. L. Blake, T. Z. Zoltai 9:25 G. L. Laberge: CARBONATE MINERALS IN THE IRON FORMATION AND THEIR SIGNIFICANCE 9:50 R. E. Randolph: SUSCEPTIBILITY MEASUREMENTS CF EMPIRE MINE MAGNETIC MATERIAL & HEMATITE CRYSTAL STRUCTURE COFFEE BREAK 10:15 Hoppin, J. C. Palmquist & L. 0. Williams: CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE ON THE LOCATION OF THE TENSLEEP - BEAVER CREEK FAULT, BIGHORN MOUNTAINS, WYOMING 10:145 R. A. 11:10 C. M. Gallick: CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA 11:35 M. A. Rogers: BIOGEOCHEMISTRY OF MINNESOTA LAKES: 12:00 LUNCH - MAIN BALLROOM, KIRBY STUDENT CENTER CARBOHYDRATES �SESSION IV R. W. Marsden Chairman: 2:00 J. H. Zumberge & 14. R. Farrand: LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY ORIENTED LAKES IN NORTHERN ALASKA 2:25 C. E. Carson: 25O 0. M. 'hwartz: 3:15 THE SUBDIVISIONS OF THE BTWABT}( FORNATTON ON THE EASTERN MESABI GENERAL DISCUSSION Saturday, May , 7:30 - Hotel 1963 Duluth FIELD TRIP TO THE MESABI IRON RANGE Field trip leaders: F. D. Effinger, Pickands Mather & Company J. 14. EmanuelsOfl, Reserve Mining Company C. L. Iverson, Oliver Iron Mining Division Richard Strong, Oliver Iron Mining Division �1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology REFINEMENT OF THE HEMATITE CRYSTAL STRUCTURE R. L. Blake.Y, T. Z. Zo1taiY, and R. E. Hessevick!" The crystal structure of hematite has been refined as an initial phase of studies involving atomic positions and vacancies in hematite during reduction to magnetite. Three—dimensiofll diffraction intenItieD were collected and automated on a spherical single crystal of hematite with both manual Buerger single crystal diffractometer. The structure has been refined with R factor of 7.1 pera least squares program and the final structure gave an cent. The structure model of Pauling and Hendricks has been confirmed with essentially no change in the iron coordinates and approximately a 5 percent change in the oxygen coordinates. The interatomic distances and bond angles were also calculated. TMinneapolis Metallurgy Research Center, Bureau of Mines 2! Department of Geology g Geophysics, University of Minnesota �2 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology ORIENTED LAKES IN NORTHERN ALASKA C. E. Carson University of Minnesota, Duluth Study of numerous thaw-lakes in the permafrost of the Arctic Coastal Plain has revealed that basin shape and orientation is controlled by winddriven waves and currents with associated thermal effects. The lakes range in size from mere puddles to basins 8 or 9 miles long, and all possess a similar basin morphology. This morphology consists of wide sub-littoral shelves and bars on the east and west sides, with the deeper central basin extending uninterrupted to the north and south ends. The ba- sins are elongated in a north-south direction, and have length-width ratios ranging from 1 to 5.1. Few basins are over 8 feet deep. In the Point Barrow area, most basins taper toward the north. Analysis of wind data from the Barrow weather station has revealed that summer winds are bimodal, being either easterly or westerly, average some 15 m.p.h., and are remarkably steady from one direction for several days at a time. orientation. Their average directions are nearly perpendicular to the axes of Investigation has shown that wind-driven wave action on the east and west sides, and the presence of circulation cells in the north and south ends, has produced the characteristic basin morphology; therefore, orientation. �3 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology CLAY MINERALOGY OF THE DECORAH SHALE, MINNESOTA Cyril M. Gallick University of Minnesota, Minneapolis The Middle Ordovician Decorah Shale is exposed sporadically in a 20-. mile wide band, extending from St. Paul to the southwestern corner of Houston It is a green-gray or less commonly a blue-gray shale that contains County. thin (generally 0.1 to 0.2 foot) interbeds and lenses of limestone and co- quina. The limestone layers are widely separated in the basal 10 to 20 feet, but increase in number irregularly upwards. In the middle of the formation, there are two or more zones, 3 to 5 feet thick, which contain limestone beds separated by less than O.i feet of shale; near the top, the limestone beds A few of the uppermost beds are become thicker and more widely separated. The formation is 89 feet thick at St. Paul and thins one to two feet thick. progressively to 25 feet at the Minnesota-Iowa border. The minerals in the grade size less than 1/512 mm were determined with "illite" (a 10 layered silicate with inter— the X—ray diffactometer to be: layers of a lL mineral), kaolinite, orthoclase, and calcite. Where all minerals are present, peak intensities indicate that orthoclase and illite predominate. The material sized greater than 1/512 mm is mostly fossil hash and At St. Paul, illite and orthoclase are present throughrare quartz grains. out the formation, apparently in constant proportions; kaolinite and calcite are sparse in the basal part but occur in significant amounts in the middle and upper part of the section. At Rochester, the basal shale contains illite or-thoclase, and calcite in proportions similar to that in the upper part of the St. Paul section and sparse kaolinite; the middle shales consist entirely of illite; beds in the upper part contain either kaolinite or orthoclase or both, but apparently only in minor amounts. The orthoclase in the Decorah Shale has been presumed to be the result of authigenesis. All illite (001) peaks on the diffractometer from the St. Paul section and from the basal part of the Rochester section are very asymmetrical, extending from 9.BA to slightly more than lLR, possibly indicating a considerIn the middle and able amount of interlayer 1L4X mineral in the structure. upper parts of the Rochester section, the illite (001) peaks are nearly symmetrical. analysis of a shale which had been weathered for possibly more This peak than five years showed only a change of the illite (001) peak. much more asympeak, broader and was lower in relation to the (002) illite X-ray metrical than that of any other shale analyzed. little more than l7R. It extended from 9.8k to a �L. UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on May 2-3, 1963 Lake Superior Geology THE THERMAL METAMORPHIC EFFECT OF THE DULUTH GABBRO UPON THE SNOWBANK GRANITE G. N. Hanson, W. C. Phinney, and P. W. Gast University of Minnesota, Minneapolis, Minnesota The effect of the thermal metamorphism of the 1.0 billion-year Duluth Gabbro on the 2.5 billion-year Snowbank Granite can be seen in the changes of the Rb-Sr ages of the biotites and the changes in the degree of triclinof the potassium feldspar in the granite. tion zones parallel the granite-gabbro contact. icity In both cases, the transi- Biotites from the granite within 2.0 kilometers of the contact (map distance) have Rb-Sr ages of less than 1.2 billion years. At distances greater than 2.0 kilometers, the successive biotite ages increase regularly to 2.55 billion years. The change in the ages exhibited by the biotite is shown to result from the loss of radiogenic strontium from the biotite strucThe mechanism for this loss is assumed to be either recrystallization ture. of the biotite structure or volunie diffusion of the radiogenic strontium out By a trial and error process of fitting theoretical of the structure. curves to the data, an activation energy of about 50 kilocalories for recrystallization by a zero—order rate process and an activation energy of 85 kilocalories for volume diffusion are proposed. Potassium feldspars at distances greater than 2.0 kilometers from the contact are maximum mirocline (maximum triclinicity) as determined by mea— Within 2.0 kilometers surement of the 131-131 spacing by x-ray diffraction. of the contact, the potassium feldspars are primarily orthoclase (monoclinic feldspar) except for several samples near the contact which show mixed orthoclase and microcline. The albite content of the potassium feldspar tends to be only a function of the facies of the stock and ranges from 0r59—0r96. The above data raise several questions which as yet are unanswered: (1) Why is microcline the potassium feldspar at distances greater than 2.0 kilometers? Could this be explained by regional metamorphism of the stock during the Algoman orogeny about 2.5 billion years ago? (2) Why did the potassium feldspar within 2.0 kilometers of the contact change to orthoclase upon thermal metamorphism by the gabbro and then not revert back to microcline upon cooling? Could this be a result of a lowering of water pressure in the stock at the time of the intrusion of the gabbro? �5 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 CONTROL BY PRECAMBRIAN BASEMENT STRUCTURE OF THE LOCATION OF WYOMING THE TENSLEEP-BEAVER CREEK FAULT, BIGHORN MOUNTAINS, Richard A. Hoppin - University of Iowa, Iowa City, Iowa John C. Palniquist - Monmouth College, Monmouth, Illinois Lyman 0. Williams - The California Company, Pensacola, Florida angic fdnlt, The Tensleep—Beaver Creek Fault (Laramide in age) is a high The north side 32 miles in length, trending E-W across the Bighorn Mountains. The fault has moved up a maximum of 1350' in the axial portion of the range. presently known is a major transcurrent fracture but is the only such feature this trend, has that crosses the whole range. Why the fault formed and has the eastern 12 miles been a puzzle. This investigation was restricted to The Precambrian rocks were exalong which the Precambrian rocks are exposed. might have been reamined to see if there was any structural anisotropy that sponsible for the localization of the fault. One is best developed near the and dips 500 This foliation varies from N.80°E. to N.80°W. in strike fault. Several zones of pervasive foliation up to 300 feet wide were mapto 70°N. is less well deAs one goes north away from the fault, the foliation ped. in width are preveloped although local zones of a few inches to five feet shear surfaces; In the field, the foliation looks like closely spaced sent. for occahowever, thin sections indicate complete recrystallization except Later, pegmatitic masses cut this sional deformed relict plagioclase augen. In the fault zone, these foliated rocks, and the sedimentary foliation. quartz cementation are rocks, are brecciated and crushed. Quartz veins and 50 feet wide. characteristic. The crushed zone is only about Two strong foliations were discovered. This The second foliation trends N.50°-65°W. and dips 60° to 70°NE. foliation is dominant to the north of the fault but is absent near the fault. This fabthe fault. It is also the main foliation in the Horn area south of plagioric is also completely recrystallized with only a few relict deformed mylonitizatiofl arid quartz veining have clases. Later, zones of crushing, straight A particularly strong cataclastic zone is followed by a this trend. This same zone conportion of the valley of the North Fork of Powder River. is probably responsible for a small detinues southeast into the fault and flection of the fault. It seems reasonable, therefore, that the Tensleep-Beaver Creek fault was formed along an E-W zone of pervasive foliation and deflected in one area along another zone of northwesterly foliation. These foliations were formed under deep-seated conditions of plastic deformation followed by reLaramide took place at crystallization. The later deformation during the shallow depth and was of a brittle nature. �6 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology THE RELATIONSHIPS BETWEEN THE DULUTH GABBRO AND THE DIKES AND SILLS NEAR HOVLAND, MINNESOTA Norris W. Jones University of Minnesota, Minneapolis, Minnesota It is tentatively concluded from onissan'e go1ogic inepping in the vicinity of Hovland, Cook County, that the Duluth gabbro complex does not exand othtend as far eastward as Lake Superior, as suggested earlier by Grout ers (1959). Instead, the gabbro appears to terminate at the Brule River. The mafic rocks along the shore that previously were called Duluth gabbro are the lower part of the Hovland diabase sill. Three other diabase or gabbro units are recognized in the area. Petrographic and x-ray studies show systematic changes in the Hoviand sill. Silica, alkalis, and iron gradually increa3e upward from the base. is present As in the Skaergaard intrusion of East Greenland, an olivine gap and the two pyroxene boundary is crossed. The compositional changes are in- ferred to indicate that the sill formed by crystal fractionation. The relations of the intrusive units in the area can be explained as the result of emplacement of Logan intrusives, followed by intrusion of the Duluth gabbro ccinplex. The Logan intrusives were emplaced along a dominant- ly northeast—trending fracture system, whereas the Duluth gabbro complex in this area strikes essentially east-west. The Hoviand area represents the intersection of these two malor structural trends. �7 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute May 2-3, 1963 on Lake Superior Geology CARBONATE MINERALS IN THE IRON-FORMATION AND THEIR SIGNIFICANCE Gene L LaBerge University of Wisconsin, Madison, Wisconsin To allow more rapid identification, a staining technique was used in studying the carbonate minerals in the iron-formation. The procedure is outlined in an to simp- article by Warne in the Jour, of Sed. lifying the identification of the carbonate species, the stain showed beauti- Pet., March, 1962. In addition fully the relationship of the various carbonates to one another, and the association of particular carbonate species with certain other minerals. Some generalizations to which there certainly are many exceptions which may be made, are as follows: Most of the siderite is primary material. The ex- tremely fine-grained carbonate which comprises up to 75 per cent of some slaty layers in the iron-formation is almost certainly primary. ial is siderite and/or very iron-rich ankerite. This mater- Textures indicate that the siderite granules, which are not uncommon, are probably primary. Unques- tionably, secondary siderite is not common. In contrast, most of the ankerite, ferroandolomite, and dary. dolomite are secon- Much of this secondary carbonate is probably a byproduct of the de- composition of the iron-rich ankerite to form magnetite, with which it is usually associated. However, primary ankeritic carbonate in both the slaty material and in granules does occur. �8 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology STRUCTURE AND STRATIGRAPHY OF THE UPPER KEWEENAWAN ROCKS IN NORTHWESTERN WISCONSIN George Moerlein Bear Creek Mining Company, Anchorage, Alaska Between the summer of 1955 and the winter of 1960, Bear Creek Mining Company explored the western tip of the Lake Superior Syncline in quest of possible copper-bearing Nonesuch formation. The area covered includes por- tions of Ashland, Bayfield, Douglas, Washburn, and Burnett Counties, Wisconsin. Field mapping, extensive magnetic and gravity surveys, some refraction seismic work, and diamond drilling each played a part in outlining the geology of the area. The normal sequence of Keweenawan sediments, Copper Harbour, Nonesuch, and Freda formations was recognized, and the tratigraphy of each formation will be discussed. The structure of the area is essentially that shown on the 1948 edition of the Geologic Map of Wisconsin, a northeast plunging syncline. however, is locally complicated by faults of major Evidence importance. will be presented which indicates that the formation of the Lake Superior Syncline, at least in Wisconsin, began in an time. This, very late Keweenaw- �9 UNIVERSITY OF MINNESOTA, DULUTH of Geology Department May 2-3, 1963 Institute on Lake Superior Geology THE STRATIGRAPHY AND STRUCTURE OF THE ROVE FORMATION, GUNFLINT LAKE AREA, MINNESOTA G. B. Morey University of Minnesota, Minneapolis, Minnesota in the South Lake Quadrang1. near Gunf lint Lake in Cook County, was completed in 1962. The area is on the north limb of the Lake Superior structural basin; accordingly, the strata Geologic mapping of Animikie Group rocks strike eastward and dip consistently five to 15 degrees south, except adjacent to the Duluth Complex where the dips increase to as much as 65 degrees. The Rove Formation overlies the Gunflint Iron Formation, apparently conformably, and is truncated by the Duluth Complex; approximately 1,800 feet of The formation consists of two recognizable lithologic units. Rove are exposed. The lower unit, about 400 feet thick, consists mainly of a black, very finegrained, thin-bedded or fissile argillite with abundant graphitic or carbonaceous material and pyrrhotite, interbedded with lesser amounts of gray, mediumThe grained, massive graywacke. Calcareous concretions are locally abundant. argillites, grayupper unit, about 1,400 feet thick, consists of interbedded wackes, and quartzites; the latter two rock types become more abundant upward in the section. Graded bedding, sole marks, intraforrnational argillite fragments, convolute and small-scale cross-laminations and clastic dikes suggest a subaqueous flow origin for much of the upper unit. A south-southwestward movement of material is suggested by many of these structures. The Animikie Group rocks contain several east-trending sill-like bodies, mainly of diabasic gabbro, which range from less than 100 to more than The sedimentary rocks adjacent to the sills are 1,000 feet in thickness. metamorphosed to mineral assemblages. characteristic of the horr1blende-hornfels facies. The sills are correlated with the Logan Intrusives; they are older than and are truncated by the Duluth Complex. �10 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 THE APPLICATION OF TREND SURFACE ANALYSIS TO THE WHITE PINE COPPER DISTRICT S. C. Nordeng1, C. 0. Ensign, Jr.2, M. E. Volin3 Over one hundred sets of drill hole data were taken from the files of the White Pine Company and coded on IBM cards. The section was divided into upper and lower halves and linear, quadratic and cubic surfaces of best fit were computed for each half for average copper percentage, thickness, and ounces of silver per ton, utilizing a taped multiple regression program on a medium speed digital computer. The linear surface for the upper half accounted for one-half or better of the departures from the mean and showed slight improvement for higher order surfaces, suggesting that the trends of the quantities under consideration are essentially planar in nature. The best fit was found for copper, The surfaces show an increase in thickness to the the poorest for silver. north and northeast, and in copper content to the southeast. The lower section showed macimum improvement in the sum of squares for the cubic model for both percent copper and thickness. Maps of the cubic surfaces successfully predict the location of a known ore body for which Departures of observed values from com no data was entered in the program. puted values for the lower half are interpreted as resulting from relative thickening and thinning of the upper part of the lower section which is relatively barren, and the lower part of the lower section in which most of the ore is found. 1 Department of Geology and Geological Engineering, Michigan College of Mining and Technology, Houghton, Michigan. 2 Chief Geologist, Copper Range Company, White Pine, Michigan Institute of Mineral Research, Michigan College of Mining and Technology, Houghton, Michigan �U UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 STRUCTURE WITHIN THE DULUTH GABBRO COMPLEX, GABBRO LAKE AND GREENWOOD LAKE QUADRANGLES, LAKE COUNTY, MINNESOTA William C. Phinney University of Minnesota, Minneapolis, Minnesota Mapping and petrologic studies of the Duluth gabbro complex in the Gabbro Lake and Greenwood Lake quadrangles during the summers of 1961 and 1962 have indicated a complex series of gabbroic intrusions associated with antiform and basin-like structures. A major intrusion in the southeast quarter of the Gabbro Lake quadrangle and the north-central part of the Greenwood Lake quadrangle is roughly elliptical in plan, has a long axis of at least nine miles, and is inferred to be cone-shaped. It intrudes anorthositic gabbro and concentric layers that dip nearly vertical at the border and nearly horizontal at the center. Regular variation in mineral assemblages from olivine rich at the border to pyroxene-rich at the center indicate a normal differenNumerous smaller gabbroic intrusions as well as zones of tiation sequence. intrusions have been mapped. has Olivine gabbro with well defined layers having graded olivine concentrations in rhythmic succession forms a broad, shallow basin in the southwest quarter of the Gabbro Lake quadrangle. Within the basin, there are many anorthosite lenses that contain numerous one- to two—inch patches of olivine, apThe eastern boundary of parently concentrated from the interstitial fluid. the basin is in sharp contact (apparently intrusive) with the anorthositic The relative ages gabbro intruded by the cone-like intrusive mentioned above. of the cone-like gãbbro intrusion and basin-shaped gabbro intrusion are not known. Southeast of Gãbbro Lake, a marker zone in the gabbro can be traced around an antiformal structure that is elongated subparallel to the basal contact of the gabbro and has an anorthositic gabbro core. In the same area, a very coarse-grained pyroxene- and ilmenite-magnetite-rich dike, that is as much as one-fourth mile wide, can be traced for several miles. �12 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology PRELIMINARY INVESTIGATION OF A PORTION OF THE NORTHERN COMPLEX, BARAGA COUNTY, MICHIGAN D. W. Pollock and S. C. Nordeng Michigan College of Mining and Technology, Houghton, Michigan During the summer of 1962, the writers initiated a study of a portion Some results of the "Northern Complex" which lies in Baraga County, Michigan. of this study are reported herein. (1) amphiboSeveral lithologic groups have been mapped. These are: plagioclase—rich gneis— lite; (2) greenstone; (3) rnesocratic gneisses and (4) varieties. ses. Each of these groups can be subdivided into more specific The groups occur in definite belts and the following gradations were observed in the field: greenstone chiorite-plagioclase gneiss amphibolite mesocratic gneiss plagioclase-rich gneisses A thin "infolded" belt of Michigamme (?) phyllite has been located west of Clear Lake in Sec. 14, R 49 N, R 32 W. The broad structural trend is an arc, convex to the west. In detail, the structure is more complex. Poles to foliation (llsdiagrams) were plotted, but with poor results. The most useful approach was to outline the structure on the basis of vertical foliation trends. The origin of the foliation reMesoscopic linemains in doubt as the origin of the rocks is not yet known. ation is only feebly developed. Investigation is continuing. of some of the many problems raised during this study �13 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2-3, 1963 SUSCEPTIBILITY MEASUREMENTS OF EMPIRE MINE MAGNETIC MATERIAL E. Richard Randolph Cleveland Cliffs Iron Company, Ishpeming, Michigan The Negaunee Iron-Formation at the Empire Mine on the Marquette Range in Michigan consists, briefly, of magnetic cherty iron-formation, magnetic cherty carbonate iron-formation, magnetic cherty silicate iron-formation and a hanging wall member containing many large clastic facies interbedded with the precipitate iron—formation. The common criterion for grading ore at the mine is on the basis of per cent weight recovery. The ore type which presents the greatest problem in grade control is the clastic facies of the iron-formation which can vary It is very difficult to distinguish in weight recovery from 10% to tl1%. macroscopic means. Close orrich, moderate and poor der magnetometer surveying is an aid to localizing large zones, but a more definitive procedure is desirable for day-to-day control. It was suggested that susceptibility measurements on the cuttings from blast hole drilling might indicate the grade of the ore in that hole more cheaply and reliably than crude Fe analyses or streamlined Davis tube testing. clastic ore material by Susceptibility is the ratio of the intensity of magnetization acquired by a substance to the strength of the magnetizing field acting on the In a rock containing magnetite as the principal magnetizable constitbody. uent, susceptibility is, for practical purposes, the measure of the amount of magnetite present. Because per cent weight recovery of magnetite is the criterion for the cut-off s between rock, lean ore and ore in the hanging wall clastic zone, a program relating susceptibility measurements to per cent weight recovery was started. The conclusions are as predicted: measurements show a broad range of values for the general area but within a limited area correlate sufficiently well to offer a rapid, cheap, reliable method for sampling blast hole cuttings for grade control. �l&1 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2—3, 1963 Institute on Lake Superior Geology BIOGEOCHEMISTRY OF MINNESOTA LAKES: CARBOHYDRATES M. A. Rogers University of Minnesota, Minneapolis Fossil carbohydrates have been found in trypical sedimentary rocks; carbonaceous organic rocks such as peat, coal and lignite; fossilized wood; insect remains; modern lake sediments; modern and ancient marine sediments; and in lake waters. Carbohydrate materials were studied in the aquatic plants, lake waters and lake sediments of two eutrophic-alkalitrOphiC lakes of central Minnesota. Both free sedimentary sugars and sugars liberated on hydrolysis were recovered. Glucose, galactose, xylose and arabinose are the dominant sugars in order of decreasing abundance in aquatic plants of the two lakes. Maxima and minima in these sugars, as well as in the content of cellulose and hemicellulose, show little relation to season of collection and appear to be characteristic of individual plant species. Acid hydrolysis of lake bottom sediments recovered the eight sugars, arabinose, xylose, galactose, glucuronic acid, glucose, rhamnose, mannose and ribose, in concentrations ranging from 19.1 to 0.1 mg/gm of dry wt. sedThe variety and amount of these sugars is believed to demonstrate iment. the importance of microorganisms in altering the carbohydrate fraction prior to stabilization and preservation within the sediment. Acid hydrolysis of lake sediments from a deep core from Blue Lake, Minnesota, recovered in order of decreasing abundance the eight sugars, xylose, glucose, arabinose, galactose, mannose, rhamnose, ribose and glucuronic acid. A natural stability series for carbohydrates in the lacustrine envifairly stable: xylose, glucose, rhamnose, arabinose; moderateronment is: galactose; very unstable: ribose, mannose; fairly unstable: ly stable: glucoronic acid. �15 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 GEOLOGIC INTERPRETATION OF AEROMAGNETIC ANOMALIES OVER PRE- KEWEENAWAN ROCKS IN CENTRAL MINNESOTA P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Isidore Zietz, U. S. Geological Survey, Washington, D. C. in An aeroinagnetic survey completed by the U. S. Geological Survey of 1961 has clarified our knowledge of the Pre-Keweenawan rocks in an area about 3,000 square miles in central Minnesota, extending from the latitude in of Little Falls, in Morrison County, south to the vicinity of Gaylord, of the anomalies In the northern part of the area, sources Sibley County. units have have been identified from scattered outcrops and separate rock been extended, based on geologic considerations and magnetic data. The aeromagnetic data indicate that the igneous rocks of the Penokean orogeny (Woyski, 19L19), which have been quarried extensively for building monumental stone in a broad area centered at St. Cloud, extend in the and eastward beneath oversubsurface south at least to latitude L5°l5' N. Northwestward from St. Cloud, lapping upper Keweenawan sedimentary rocks. and schist appears to be the dominant bedrock. In the southern part of the area, outcrops are lacking and interpretation of the magnetic patterns is more equivocal. Except for an anomaly at above igneous rocks of Lake Washington in Meeker County, which probably is mafic composition, interpretation of the magnetic anomalies intermediate or of the baseis not attempted. South of Hutchinson, a change in the trendmarked discontiby the magnetic pattern, suggests a ment rock, as indicated nuity, possibly a fault or an unconformity, in the Pre-Keweenawan rocks at this latitude. �16 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geo1gy May 2-3, 1963 STRUCTURES OF CONCRETIONS IN THE THOMSON FORMATION CARLTON AND PINE COUNTIES, MINNESOTA Paul Weiblen University of Minnesota, Minneapolis, Minnesota Calcareous concretions in the Thomson Formation found in the vicinity of Carlton are of two types. The concretions in graywacke and graywacke—iate beds consist of massive calcite, are ellipsoidal, and lack a distinctive internal Those in structure other than bedding, which conforms to the enclosing rock. finer-grained slate beds are zoned; they contain an inner core of slaty mater— ial, surrounded by well—crystallized calcite or by quartz with sutured grain The outer zone has a pseudo cone-in-cone structure, defined by boundaries. bands of slaty material. The calcite in both types of concretions replaces quartz and feldspar. The zoned concretions on the limbs of folds in the slate and graywacke succession are rotated out of the plane of bedding. The c axis of the calcite in the pseudo cone-in-cone structures is oriented parallel to the direction of maximum compression and a cleavage, which is well developed, parallels shear These features afford a promising means for further study of directions. structural relations in the formation. Remnants of concretions are found in the more intensely metamorphosed phases of the Thomson Formation southwest of Carlton, in phyllite, metagraywacke, and mica schist. Quartz has replaced the calcite in phyllite. Well—zoned concretions occur in the metagraywacke. The outer zones of these consist principally of hornblende, garnet, quartz, and andesine; the cores contain mainly epidote, quartz and andesine. Sections of the cores show that they are deformed into boudins. They also contain characteristic S-shaped structures formed by shearing and defined by heavy mineral concentrations. These similarStructures similar to these occur in the slate and phyllite. the concretions can be ities indicate that further sampling may show that Formation. used as stratigraphic marker beds in the Thomson Remnant calcite is found in the concretions in the mica schist, metagraywacke and phyllite. The (211) spacing of the calcite ranges from 3.04 angstrorns in the slate to 3.02 angstroms in the schists, indicating the occurrence of relatively pure calcite (less than 5 percent Fe,Mg) throughout the entire formation. Plagioclase coexisting with calcite ranges from An5 in the slate and graywacke to An40 in the mica scist and metagraywacke. It has been found that radiographs afford a practical method for studying the internal structures of the concretions. Fluorescence excited by electron bombardment provides a mean of distinguishing calcite from dolomite. �17 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology May 2-3, 1963 Institute on Lake Superior Geology BURIED EXTENSION OF THE KEWEENAWAN BASIN IN MINNESOTA GEOPHYSICAL STUDY A Isidore Zietz, U. S. Geological Survey, Washington, D.C. P. K. Sims, Minnesota Geological Survey, Minneapolis, Minnesota Approximately 30,000 linear traverse miles have been flown eromagnet— ically by the U. S. Geological Survey across the "mid—continent gravity high". This is, perhaps, the most oustanding gravity feature in the United States, extending from near Lake Superior in a southwesterly direction to the Sauna basin in Kansas. Coupled with the gravity measurements and meager drill hole records, the aeromagnetic data strongly, if not unequivocally, imply the existence of a several-mile-thick accumulation of Keweenawan lava flows, extending uninterruptedly for 800 miles, f tanked by Pre-Cambrian sandstones which locally may be more than a mile thick. Total thicknesses of lava flows and neighboring sandstone can be estimated from the gravity data, whereas the aeromagnetic data supply the details of the configuration of the upper surface of the flows. In Minnesota, the magnetic data clearly outline the Twin Cities artesian basin, an elliptical trough 60 miles long in a northeast direction and 30 to 35 miles wide. basin and north of latitude LL°35' N., At the eastern margin of the the magnetic data suggest that the basin is bounded by a narrow northeast-trending horst of mafic volcanic rocks, probably elevated at least 1,000 feet above the adjacent rocks. The horst is the basement manifestation of the Fiudson-Afton anticline, a northeast-trending Paleozoic fold. In southern Minnesota, south of latitude L44°l5' N., the mafic lavas are at considerable depths, but the surface of the flows rises to within 1,500 feet at the Iowa border. �18 UNIVERSITY OF MINNESOTA, DULUTH Department of Geology Institute on Lake Superior Geology May 2—3, 1963 LAKE SUPERIOR CORES AND BOTTOM TOPOGRAPHY James H. Zumberge and William R. Farrand University of Michigan and Columbia University to Cores were recovered from eleven drill holes in water depths of 500 drilling 1,130 feet in Lake Superior in 1961 and 1962. A shipboard, rotary and to lorig was used to penetrate the unconsolidated Pleistocene sediments The sediments were recovered by gravity and piston cate the bedrock surface. coring -- continuously in the upper 30 feet and intermittently below that depth. reaching bedThe longest core penetrated 686 feet of sediments without sediments rock, and it shows at least four alternations of glaciolacuStrifle The other cores penetrated only 7 to 156 feet and the varved), red lacustypical sequence was gray, lacustrine clay (lower part trifle clay (some varved), and red clay till. Below the till, well—washed and red, clayey till. red and sand (outwash?) was found in three holes, and in four other holes white (Cambrian?) sandstone was reached. drill A sub-bottom depth recorder was used in combination with the topography. Near logs for the interpretation of stratigraphy and sub-bottom broad bedrock valthe Minnesota coast, more than 700 feet of drift lies in a valleyIn the eastern part of the basin, strong north-south trending ley. modified stream and-ridge topography appears to be a submerged, glacially system, rather thinly covered with glacial drift. Also, the possibility of strong east—west faults between Keweenaw Peninsula and Sault Ste. Marie is indicated. � https://digitalcollections.lakeheadu.ca/files/original/5a175e5c561d413faf02a1b640ea415e.pdf c174ae149f6d8beb5546748ab48f1a3a PDF Text Text Field Trip "Stratigraphy of the.Biwabik Iron Formation 11 Sponsored by the Lake Superior Geology Club Duluth, Minnesota May 4, 1965 �,, ~~ G>,._ /<I AUBURN ~t-«~ 1-/19 19/11. G' . G'-'9 ~ )'1- ~ 0 '9</ ~ O,s- +-~ ~ -v~ ~,o -v~~ <? INDEX MAP OF THE MESABI DISTRICT , MINNESOTA �FOREWORD Gentle reader, take heed, the field trip which you are about to take - not a polished affair with textbook illustrations and trip leaders able to J ve glib expla.ne.tions for everything you are going to see. o the gene al objectives for which the Lake Superior Geology In keeping with stitute was or- g nized, that is, to present preliminary r e sults of investigation in new areas of geologic interest, the leaders of this trip plan t o show you their approach tp subdivic1:1.ng the Biwabik iron formation beyond the basic fourfold subdivision ~rst proposed by J. F. Wolff in 1917. That the problem of further subdivision i ls difficult can be accepted si nce such authoritie s as Gruner, Grout and Broderick, E te , Schwartz and Gunderson have all come up with systems that many individuals use but which do not appear to be generally acceptable to all 'rorkers in the ield. In such a situation we may expect considerable discussion and disagreement i th any system proposed. ~Y emerge, Perhaps in the anticipated clash of opinions the truth. but don't count on i t. In any event the trip should be instructive " o both you and the leaders, and perhaps even entertaining to the philosophers rong you contemplati ng the state Of geol ogic knO'£o7ledge concerning this 1 the ,randfather of all iron for-mations. . A secondary but highly interesting part of this trip \d.ll be the 1ppo1~unity to observe the changes vmich take place in unoxidized iron formation rom the Eveleth area eastward almost to the contact of the Duluth Gabbro. T~~s spect of the trip should be of particular interest to students of metamorphism and those less c,o ncerned with the local problems of iron formation stratigraphy. lble controversy exists even in this area, the individualists among you vTontt I q.ave to accept any of our leaders' statements since the rocks themselves \-Till be tvailable for identification and collection. Due to the unexpectedly large number of people participating in this trip, we are antici pating some difficulty in maintaining our schedule of arrivals and departures f rom each stop. ~orn blows . compensation. Please return to the buses promptly a fter the I f you are left i n the pit don •t panic, apply for unempl oyment �The field trip will start at 7: 50 A.M. at Hotel Duluth and proceed rectly to the Auburn Mine property outside of Virginia . Upon completion of tq.e one stop at Auburn , the buses ldll ta.k.e us to the Erie property and proceed through four stops in various parts of the pit. Two stops are planned in the I REf Serve property to complete the program for the day. The buses will return to Duluth via Aurora and deposit passengers at the beginning point. Passengers 'rushing to remain on the Range should make private arrangements for transportation ftam the Reserve property or possibly from Aurora. It is anticipated that we ,dll finish the trip around 6:00 P.M. Lunch ~dll be served at the third stop in the Erie pit and rest stops are planned on ent ering the Erie property and leaving the Reserve property. Please read, consider and observe the regulations on the following page to which ~rJ have agreed in order that we can gain entrance to the various properties. �ruiruuTIONS: Through t he courtesy of the Oliver Iron Mining Division, United States Steel Corporation , Pickands Mather & Co., and the Reserve Mining Company, we have beFn granted permission to enter, inspect and collect small specimens on their rebpective properties. t~ In return for this privilege, we have agreed to abide by following regtuations which apply not only to visitors but also to all company pe~sonnel. l. pits. Safety hats and goggles will be worn at all times while in the various You will be issued such equipment at the first stop. This equipment is charged out to the Lake Superior Geology Club and we will have to pay for it if it is not returned at the end of the trip . 2. Picture taking of equipment is discouraged in all active pits and all pictures forbidden on the Reserve property. at the entrance to the Reserve property. for the fun of it . Arrangements will be made to check cameras Please do not try t o outwit these regulations You may make it difficult for future geologists to enter these interesting areas . 3. Please use caution when approaching rock walls . The talus slopes are notoriously unstable footing and rock slides from the walls above are not uncommon in the spring. While the purists among you will want to remove specimens from the living rock, let us remind you that \dth taconite, it ' s going to take a lot of hammering. We have a long, tO'\.lgh day ahead of us, so save your strength. also applies to potential mountain goats climbing up rock faces. Thi s You may endanger yorrself and other people as well as delay the trip , so stay off high faces. 4. Please use discretion wnen hammering on rocks near other people . Taconite is tough and hard. at high speed. Sharp chips have a tendency to fly in all directions The safety goggles supplied you are not just a bureaucratic detail. Us~ them at all times and make your arm on Minnesota taconite. sure they are on people near you before you t est It is reported to have an average crushing stkength of 55,000 pounds per square inch . �Ea ster n Biwabi k Str atigraphy f rom Gunderson a nd Schwartz .Minnes ota Geological Survey Bulletin 43 -~ z;~a ~ ~~ !I ~~! ;- s ~ -'C-Q; ~ ..~ ~ GENERALIZED COLUMNAR SECTION OF THE BIWABIK IRON-FORMATION ~ ~ -~ ~ ~ £ r: ~-:! == j -!!cri ~ ~ ? ! -0f:i!..._ou E~ ~ r ~ s o ~ ~ -- J: j IN THE EASTERN MESABI DISTRIC T, MINNESOTA i? 1-- - -- - - --------=---,--.,-,--- - - - -- - - - - - - - - l 6 i ·~· ~:g 32: c.5 Descnption of Submembe rs ;; .:...: w - Q (Notations cO - Jf ~ J I B {!6) (eo~t} and (we!:> I) refer to orcas near the easter n and western drill holes) calcite marble,. minor diop side, wollastonite , id oc ro s e, andradit e and quartz j """-;;;;ered (di'op/;ide) chert taconite locally wilh hornblende, hedenberq ite and some cummingtonite a nd oc tmol•te /ami'n aled (ferrohyperslhene - moqnel i le) c;uarl.t ! aconite with hedcnberqite c >~ w (l_ (l_ ::J taconite {west) I /:::,vy laminated (oclinoh'le-moqnefite) chert taconite 1-:---:-::::--fV ··-·tonile ond minor hedenbc rgi te -' (/) cr laminated (cummin91onite - mognetite) chert and loyoli te (east) and (421 "' .D :> <I 0 (71 E 161 F (201 with abundant granule struc tures and locolly w ith quart zfilled seplorio s tructures; m inor magneti te, c ufT'ming tonite and o ttinolite shaly bedded (cumminqtonite-maqnetite) quartz laconile hedenocrgite (cost); locally abundant w•l h minor andradite cumminglanite (west} quartz taconite (ea st) and mol/led (andradite) quartz obundonl magne ltl e - bearing granules throughout G (251 wavy layered (actinolite? -maqnetite) quartz taconite f---:1 J wit~ cumminc;~- quartz taconite r----t--__ond H locally liOl local ly with foyoli te (eas t) taconite (west) with with minor hedenberq:itei and cummingtonite (wes t) .,--+ - - (Sl (l6 ) " ' alq~l (moqnetile) quorlz toconife with abundant magnetite- r ich granules ond "---: ebblcs; conglomcrolic fabric throuc;~houl; minor hematite r---+-_ granule (maqneltle) quartz facomle with obundonl magneti te - rich pebbles ~top and thic kly layered (magnel!le) quoriL tocomle near bottom >- K (351 L (301 near wavy layered (silicole moqnelite) quartz taconite with abundant moQne tite· rich granules ond ptbblcs ; silicates ore actinolite ond ferrahyperslh ene (east) ond cummingtamte (we st) 9 1- cr w I u wavy layered (st'licote-magnett~e) silicate-quartz taconite with abundant mag netite-rich granules ncar bollom; silic.o tes with magnetite ore ferrohypersthcne and hor nblende (e o:o t) and cumming toni te and actinoli te (wes t); silicates wi th quartz ore fcrrohypers thene (cost) ond c umminqtonite (west) cr w (l_ (l_ ::J layered (maqnelt~e) loyolite-quorlz /acon/tc with fcrrohypersthene layered (maqnel/te) cumminqtom~e-quar tz tacom~e (wes t) M (201 N 41 0 (17) foyalde -quartz tacomle tocomle (westli minor with ferrohyp ersthene (eosl) and {eas t) and cumminqlomle-quorlz mac;~ne t ite bedded granule (magnetite) quortz - loyolile tacomle with some fcrrohypers thene and minor cummingtoniti! (cost) to quartz -cumminqtom~e focamle with · moogranules (west} ~et ite -beoring r: sholy quortz- foyoli!e tocomle cumminqlontle taconite 10 foyoltle tocomle (easJI and sholy quorlz- to cummingtont~e tocom~e (west); minor moonetite '!!aceous grophite -sikcote-quortz laconlle with abundant ferrohypersthene and minor foyolite, biotite, olmondilc ond pyrrhotite (eosl) and traces of pyrite, pyrhotit e and cummingtonite (wes t) . layered (magnetJ/e) loyolite -quortz taconite with m inor cumminQtonite ered (moqneflle) quorl.l taconite with minor cummingtonite throuq:hout, and hedenbcrgitc and some l oj!alite (east) ljr;;nule (magnetite) quartz taconite 1---+---+-- --flj r-minor f-,---:-:-:-i(/ (;;ered and granule 'j -, locotly, with minor cummingtonite throuqhout, ond foyolitc least) (moqnetJ~e) cummingtom~e-quorlz taconite with hedenberqite ond some fayolite (cos t) ~rlz f-;-;---;-o;;-( FIGU!\1': 5. - taconite with minor hedenbcrgite and cummingtonitei clastic quartz p ebble zone locally at bose Generalized columnar section or the Biwabik iron-[ormation. };j �sw - sw 28-58 - 1 7 S E -S W 1 7-58-17 ·. N W - NW 20-58 - 1 7 .r. - I . I 1/ v ~I , - ------ -- - ---- ---/+-- ---- / / : I I SW-N W ) 20 - 58-1 7 I I S E - NW 2 0-58 - 1 7 I G E O LOG I C M AP OF AUBU R N M I NE N SC ALE } . 1" - ·4 00' a. 0 --+--· ---- ~----· -·-· -·t--· --+--1 I I I l_ __ L E GE ND GEOLOGIC C O N TA CT S ( A PPRcJX I MA T F) ~ O VE R DU R OEN ____ ...,. CRE ST OF BA NK ..- ___ _... T OE O F B ANK �STRATIGRAPHIC S~UENCE IN THE BIWABIK IRON FORMATION AUBURN mNE 'lhickness in feet 1 UJ PER CHERTY MEMBER 16. 2 Jaspery, conglomeratic and algal chert (G and 15 . 14 13. 12 . + 10. submember I) 10 (est . ) Covered interval 10 (est.) Nodular hematitic chert beds interbedded with laminated hematite-silicate- magnetite beds 48 +'l Laminated hematite- silicate-magnetite beds with subordinate jaspery chert beds and lenses 31 Jaspery, conglomeratic chert beds interbedded with subordinate laminated hematite-silicate~magnetite beds 28 Cherty taconite ld th thin irregular ma.gneti te beds, magnetite mottles and disseminated magnetite 16 143 SIM'Y MEMBER ll. s 3 Laminated silicate magnetite tacom. t e with subordinate silicate chert lenses Laminated non- magnetic silicate taconite, fissile in part. 6 ' of fissile "intermediate slate" at bottom (G and S submember Q) lOl 37 ---:l::-:38=- LOWER CHERTY MEMBER I 9. Cherty taconite with irregular magnet ite beds . Upper 10 ' dark·~ colored silicate rich beds instead of magnetite beds , making base of lower slaty somewhat indefinite . 37 Mottled silicate- magnetite chert with chert "pebbles" and abundant coarse granules. ll Cherty taconite with thick (l"!) magnetite beds and mottles 84 has 8. 7 6. 5. Mottled cherty taconite vlith thin, very irregular magnetite ~ds. u Thick jaspery chert beds interbedded w1 th varying proportions of thin, regular laminated magnetite-hematite- silicatecarbonate beds . 66 �l Thickness in f'eetl CIIER1'I' MEMBER (Cont'd) 4. Thick hematitic chert beds with subordinate la.minated zones. Some clastic sand grains near bottom. Much carbonate. 8 Jaspery, conglomeratic and algal chert w1 th subordinate laminated zones. Sand grains common. 4 2. Massive chloritic (or hematitic) sandstone 8 1. Jaspery, conglomeratic and algal chert 4 3. 236 Total thickness exposed mGAMA ,.. QUARTZITJt~ 517 Base not exposed 1. Units 15 and 16 measured on bank between truck road and railroad near entrance to pit. Units l - 5 measured on SW bank, at SE end of' pit. Remainder measured above railroacl. 2. Unit numbers correspond to numbers pa.inted on the walls of' the Auburn Mine and are not intended to be a new stratigraphic system. 3. The lower slaty-upper cherty contact is not well-marked and disagreement exists as to its position. �__..... ...--- ERIE MINING CO MPANY / MAP OF ? PLANT AND PIT / / / I AREAS LEGEND I COARSE CRUSHER 2 FINE CRUSHER ,3~ CONCENTRATOR 1)PELLET PLANT , §\LOADING POCKET • 6 STOCKPILE 7' GENERAL SHOPS ' ,\ WEST PIT BIWABIK IRON FORMATION VIRGINIA FORMATION ::," 1;- 1 {! { DULUTH GABBRO �STOPS AT ERIE PITS Stor. At this stop, we have the base of the iron formation in the West Pit. The gama quartzite and the basal algal layer and conglomerate can be found in the roa • The alternating chert and argillaceous layers of submember V are exposed in the outer op. ' Fok The bank at the south edge of the pit is the Lower Slaty material P&Q. The r efore, the widt h of the pit here is the entire Lower Cherty member. 1 Sto J 2. This stop shows the upper part of the Lower Cherty ore horizon. The submember R can be seen along the top of the bank. It is greenish in color and !contains much minnesotaite and greenalite. Iead D irectly below this is the wavy bedded submember R. This is more noti ~ eable toward t he west, (containing abundant granular jasper). J The mottled submember S is below this layer. This submember occupies most of the lower part of the bank. It also contains much jasper as well as the con J. picuous pink to red carbonate mottles. J StoR 3. At the east end of the cut, we find the even bedded (U) and the alternating ma~sive and slaty submember (V). The massive layers consist almost entirely of ryedium grained green silicates . Some granular jasper and flinty black chert occ j rs. Minor amounts of sulfides are present. I Proceeding westward, we encounter the lower wavy bedded submember (T) and the mottled submember (S). Here the mottles consist of fine grained sili ~ ates instead of the carbonates seen in Stop 2. StoJ 4, This stop is in the upper part of the Lower Cherty member and shows submembers R & S . It correlates with Stop 2. The effects of the gabbro to the sou~heast are quite apparent. At the extreme east end there are abundant sulfides and Jvery coarse grained dark green silicates. Proceeding westward along the cut the grain size decreases and buff colored silicates (ferrocummingtonite) begin to app~ ar. The cut immediately to the south is in the Lower Slaty horizon (P). This :::t~::::u~ ;~~: ::~::::h::8 :les:;here Sto~ and shows recrystallization. Small 5. At this stop, units 0 through K can be observed. Representative blocks of e t ch subunit are marked. Locally abundant coarse grained silicates and some sulftdes occur. A few blocks show portions of jet-pierced holes. Some septaria are !e vident. �STJ ATIGRAPHY OF THE BIWABIK IRON FORMATION AT THE ERIE MINING CO. Pr oda~l:n~eo:::~ation ,.. A. Calcite - marble layer. B. Lean quartz and silicate as irregular zones and layers. U:PP+r c. s..a t y (3 - 16) (10- 35) & D. Laminated zones of magnetite and silicate interlayered with thinner chert layers. (30 - 50) E. Massive granular chert with disseminated magnetite and occasional magnetite-silicate layers. Septaria. (5 - 10) F. Similar to C. & D. but the chert contains much disseminated magnetite and granular jasper. (25 - 35) G. Massive with much disseminated granular magnetite and jasper. Locally concentrated into irregular granular layering. Conspicuous carbonate or silicate mottles. (15 - 20) H. Similar to above except more abundant granular layering. Layering becomes more laminated toward bottom. ( 10) I. Algal structures and conglomerates. J. Granular. Similar to G. & H. but more abundant disseminated granular magnetite. Carbonate - silicate mottles are very con• spicuous. (5 - 15) ;..!, h (3 - 10) Upple r K. Cherty Thin, irregular and discontinuous magnetite layers having distinct boundaries separated by thicker massive layers of lean chertsilicate. The diabase sill is within this unit. (28 - 48) L. Moderately thick layers of laminated magnetite and silicate separated by equally thick layers of chert with much disseminated magnetite. ( 30 - 40) M. Thin, well defined magnetite layers similar to K. with more magnetite occurring as granular layers and disseminated magnetite (20 - 45) N. Not recognized. o. Alt ernating laminated magnetite - silicate zones and chert layers. Similar to L., but with increasing disseminated granular magnetite in the chert toward the bottom. Conglomerate near base • ( 15 - 3 5) 'l �-2- Pilobable Correlation to Gunderson L~er P. Massive granular silicate unit with vague layering. (75 - 90) Sl/a ty Q. Black, moderately laminated argillite. R. Upper unit is massive with granular silicates in a chert • silicate matrix. Lower unit is similar to above with scattered tnirt layers of magnetite and disseminated granules. (20 - 35) s. Irregular zones and mottles of dense and granular magnetite. Much disseminated magnetite in the massive chert. Abundant carbonate or silicate mottles. (15 - 35) L wer Ta Cherty I . u~ v. (5-45) = L lern?ed, st/1!- Thin irregular layers and granular concentrations of magnetite within thicker massive chert layers. Occasional mottles. (20 - 35) Magnetite occurs in even bedded iaminated zones wfth s~lica~e and argillite and/ or as even bedded concentrations of granules iri the chert. (15 - 30) Thick laminated zones of hematite, magnetite, silicate and argillite alternating with massive granular chert layers. Conglomerate, algal and/ or slate usually occur at the base of this member. (6 - 30) �RESER 'E ' B BABBRlY~ A MONHESOTA LAKE SUPER UOR PNST i'V'Uli'E Of EOLOGY fiElD fRIP MAY 4B ~923 NERAt.: RESER VE MiNING COMPAN~ ~OLUCY DOES NOV PERMIT POSSEIIION OF CAMERAS ON VHE OPERVYa Oft PLEAS£ CHECK YOUR CAMERA WITH PLANT PROTECTION AV VHE MAIN GAV Eo i: PLEASE AVOID SVANDtNG 'tOO CLOSE UNKS ON VOP OF VHE WALL~ 0 YHE NOR'ti'H AND SOUTH WALL o MAKE CLOSE INSPECTION OF THE WALLS ll..ARGt VACON II 'II'[ UN ADDI T ION NAZAROOU~o AYO»O CLRMB ING ON VHE MUC PILES AS THE RE IS A POSSIBILITY or DtSLODGING CHUNKS VACON VV'Eo APPROXIMATELY 85 FEET OF ijpp R CHERTY AND 35 THE BAlE OF VHE NORTH WALL VO THE VOP OF THE YHE ~LWTH GABBRO LSE EN LY VHUS REGUON ABOWV 3 OUVH WALLo TH A FEW ~~NORED FEET TO VHE $0UVH UN VH t EXHUBtV~ EPRE~ENVr O FEEV OF ijpPER St.ATY ARE STRATA AREA o GENER£L L ~ CoN E- A HIGHER DEGREE OF METAMORPHISM THAN STOP No o 2 WH i CH MULE$ VO VHE WE~To ~GNEVITE AND QUARTZ ARE VKE PREDOMI NANT MU NERALSo H DEN8ERGtTE 1 FAYAL ITE, ACV tNOLIVE, FE RROHYPERSV HoWEVER, COARSE GRA U N~ Of NE AND HORNBLE NDE ARE COMMON c UNT BLACK HiSINGERI TE CAN 8E SEE N IN YH£ NORTH WAL lo IT tS ONE OF THE LAST StLICA~ E Tp FORM IN V~E BIWABIK HRON f ORMATION AND CUVI THROUGH ALL PREVIOUS MINERAL ASSEMBLAGE o ~NOERSEN AND SCHWARTZ AVVRUBUVE VHE roRMAVtON ~ OtNBERGIVE 8 FERROHYP£RSVHEN£~ ~EGMAYHTE WEINSo EiSENV4AllY OEFLY ~r Ywo COM~OSED CF HORNBLENDE AND CU VYPES OF VEI NS ARE Q~ARVZ AND ~UNK or MEDIUM fO COARSE GRA INED M~NavONI E~UOENV I TO fHE IN VHtl AREAo ALKAL I FELDSPAR o tNJEC~tON OF THE AC IDIC VE INS fHE MAFIC VEINS CON IIV HORNBlENDEo 2: W[ ARE ABOUV NORVHEA~V 3 WALLo Ml E VO fHE WE@V OF SVO~ Noo ~e A MONOCL WNAL FOLD II VID NV IN �I ~rD NERALLY FINER GRAt MAGNET IV~ SI ZE II PREVALENT I N THIS AREA Q MN ADDITION vo QUARVZ CUMMINGVONRTE, ACVINOLUTE AND ANDRADIVE ARE COMMON MONERALSo OTHER F A URES VO NOTE IN VHOS AREA ARE THE £LG L ZONE &NO A SMALL DIABA E DUKE I ~ICH TRENDS SE-NWo ,,6oo FEET A LARGER DIABASE DIKE ABOUT 35 FE WtD£ OCCURS APPROXIMATELY W SV AL ONG THE PIT CENTER LINE FROM fHE EA T END 'LSO VRENDI SE-NWo or VHE PITo TH~S DIKE � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1963 Description An account of the resource Institute on Lake Superior Geology. University of Minnestota, Duluth, Minnesota, May 2-3, 1963 Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1963 Contributor An entity responsible for making contributions to the resource R.L. Blake T.Z. Zoltai R.E. Hessevick C.E. Carson Cyrill M. Gallick G.N. Hanson P.W. Gast Richard A. Hoppin John C. Palmquist Lyman O. Williams Norris W. Jones Gene L. LaBerge George Moerlein G.B. Morey S.C. Nordeng C.O. Ensign M.E. Volin William C. Phinney D.W. Pollock E. Richard Randolph M.A. Rogers P.K. Sims Isidore Zietz Paul Weiblen James H. Zumberge William R. Farrand Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/da466cb83dd892048eea446819b1c3c8.pdf f302183e88d2b2ae53f079a2cc2d4694 PDF Text Text Tenth Annual institute on Lake Superior Geology t a —,1 ISHPEMING, MICHIGAN MAY 6-7-8-9, 1964 ��PROGRAM & INT)EX Wednesday May 6 1:00 - 2:00 PM ES.T. REGISTRATION at the Mather Inn Two concurrent field trips to the Republic and Empire 2:00 PM (Hard hats and glasses required, Field clothes Mines respectively. reconmended. Ladies must wear slacks and low heels) At the Republic Mine, the upper (stratigraphically) 500 feet of the This ore consists Negaunee Iron formation is mined by open pit methods. of alternating bands of quartz and coarsely crystalline specularite with In this area, the lower part of the minor magnetite and silicates. Negaunee consists of coarse iron silicates and magnetite. The Negaunee is overlain unconformably by the Goodrich quartzite which is in part rich enough to be mined also. The metamorphic grade is believed to be In the plant, this ore is high, possibly above the sillinianite isograd. crushed and ground to liberation by standard techniques and the iron is concentrated by flotation. The final cleaner flo,v.t after regrinding is made after conditioning the pulp at the boiling point. The concentrate is then filtered, balled and fired in a grate-kiln. The annual capacity of this operation is 3,000,000 long tons of pellets. A the Empire Mine, a 900 foot section in the lower part of the Negaunee Iron Formation is mined by open pit metho!s. The ore consists of thin, even-bedded alternating layers and mixta of fine.-grained quartz, magnetite, iron carbonate and iron silicates. The area is in the chlorite zone of metamorphism. This ore is crushed to nine inches and then the magnetic portions are reduced to about 95 7. — 500 mesh in two stages of autogenous milling. The magnetite is concentrated on drums and in tank-type hydroclassifiers. The filtered concentrate is balled and than fired in a grate-kiln. The annual plant capacity is 1,200,000 long tons of pellets. 7:00 - 9:00 PM REGISTRATION at the Mather Inn. Thursday, May 7 10:00 I4 E.S,Tb REGISTRATION at the Butler Theatre,Main St. ,Ishp. 8:00 8:30 - 9:00 AM BUSIIIESS ETING 9:00 - 11:45 AM TECHNICAL SESSION Chairman: C.E. Dutton AEan(!NETICSURT:y OF THE MARQUETTE IRON RANGE, REPUBLIC TROUGH, p. 1 AN-- 3. E, Case ADOANT AREAS, MIC Mm STRUCTURES IN THE IATERN PART OF THE MARQUETTE SYNCLINORIUM p. 3 —-3. E. Gair STRATIGPAPHY OF ANI1IKIE (Formerly Huronian) ROCKS EAST OF TEAL p. 5 TAKE, NEGAUN'E, MICHIGAN-- C. E. Fritts ThIND 'fi.FACE ANALYS OF TRACE ELEMENTS IN PEGMATITES IN MARp. 9 QUETTF C)UNTY, MICHIGAN,-- S.C. Nordeng and A. K. Snelgrove SOE SEDINENTARY INTERPRETATIONS OF GRANULE SIZE DISTRIBUTIONS p.11 IN THE LAKE SUPERIOR IRON FORMATIONS.-- J. T. Mengel, Jr. II �Thursday, May 7, coat. THE POSSIBLE ROLE OF LIFE IN THE FORMATION OF THE GUNFLINT IRON FORMATION, PORT ARTHUR REGION.-- WW, Moorhouse 12:00 - 1:15 1:30 — 5:13 M LUNCH at the Mather Inn. ?MTc11NICAL St!SI0N Chairman: D.W. Lindgren STRUCTTA1.. E ONTARIO C.OGY OF THE SKIBI LAKE IRON PROPERTY, NORTHWESTERN GEOL:f OF : AND THE ICA$ ANCIENI STI p.17 FL'E AREA, WISCONSIN—MICN.—— C.E. Duton p.21 PINE VER (BREAIATER) QUA:ri; 'COMERA QUART2L'i, FLORENCE COU?TY, WSCON.--T.H.N;.!sen.p.23 1M CHANNELS AND THEIR EFFECT ON MINE PLANNING AND GRADE CONTR(iL AT THE WHITE C.O. Ensign, Jr. THE UQJE OCCURRENCE ATIKOIAN, (Y:TARIO, -- M. PINE MINE, MICHIGAN.-- J.W. Tranmiell and p.26 OF HEMATITE AT CANADIAN CHARLESON LTD., p.27 W. Bartley LANDS LiYNG AND RIVER EROSION AT V!CTORIA GENERATING STATION, ONTONACON COUNTY, MICHIGAN.-- 3. M. Neilson ORIGIN OF THE TIGERTON ANORTHOSITE.--L. N. Weis RAPAKIVI-TYPE GRANITES OF THE AMBERG AREA, WISCONSIN.--J.A.CAIN ARVON SLATE DEPOSITS, BARAGA COUNTY, MICHIGAN.-- Kiril Spiroff 6:00 PM p.13 SOCIAL HOUR, p.30 p.31 p.32 p.33 Mather Inn 7:00 PM ANNUAL DINNER, featuring a talk on EXPLORATION--FROM ANOMALIES TO ZANZIBAR by R.H. Pemberton, Director, Exploration Division of the Aero Service Corporation. Mr. Pemberton will also shoi a new Aero Service movie titled "PATHFINDERS". Friday, May 8 8:45 - 11:45 AM EIS.T. TECHNICAL ESS,_Chairman: E. N. Cameron MICHIGAN TECH'S METHOD OF TEACHING MINERALOGY.--Kirtl Spiroff PETROGRAPHIC ANALYSIS OF MESABI NON-MAGNETIC TACONITE USING THE POINT COUNTER.-- R.E, Lubker PREPARATION OF MINERAL SPECIMENS FOR ELECTRON MICROSCOPY.-V. L. Doane ALTERED SPODUMENE OF THE LITHIUM PEGMATITE DEPOSITS OF THE GEORGIA LAKE AREA, ONTARIO.-- E. G. Pye and V. G. Mime CLAY ALTERATION AND OTHER COORDINATED GEOCHEMICAL STUDIES IN THE UPPER MISSISSIPPI VALLEY ZINC DISTRICT.--A PROGRESS REPORT.4A.V. Heyl, 3. M. Hosterman, W.E. Hall, 3. C. Green CURRENT INVESTIGATIONS OP THE PRECAMBRIAN ELY GREENSTONE IN NORTHERN MINNESOTA.-- 3. C. Cree* 12:00 - 1:15 PM LUNCH at the Mather Inn. III p.34 p,40 p.41. p.42 p.46 p.48 �Friday, May 8, cent. 1:30 - 5:15 PM TECHNICAL SESSION Chairman: W. C. Kelly GEOLOGIC AEROMAGNETIC INTERPRETATION OF PART OF ONTARIO LYING NORTH OF LAKE SUPERIOR.-- A. S. MacLaren and S. Duffel PRESENTATION OF A REGIONAL AEROMAGNETIC MAP OF WISCONSIN.-- R. Patenaude A METHOD FOR COMPUTING THE MAGNETIZATION OF DIKES WITH EXAMPLES OF ITS APPLICATION TO DIKES NORTH OF COVINGTON, MICHIGAN.-- G. VanVoorhis and L. 0. Bacon THE APPLICATION OF RADIO FIELD INTENSITY MEASUREMENTS TO MAPPING PRECAMBRIAN GEOLOGICAL FEATURES.-- C. E. Kerman and Fl. 3. Hinze INVESTIGATION OF THE THICKNESS OF THE JACOBSVILLE SANDSTONE BY SEISMIC REFLECTION METHODS --A PROGRESS REPORT.-- L. 0. Bacon THE APPLICATION OF INDUCED POLARIZATION PROBING TECHNIQUES UNDERGROUND: MICHIGAN NATIVE COPPER DISTRICT.-- AU. Schillinger THE AGE OF THE DULUTH GABBRO AND THE ENDION SILL BY THE WHOLE-ROCK Rb-Sr METHOD.-- G. Faure and P. M. Hurley THE PENOKEAN FOLD BELT NORTH OF LAKE HURON.-- G, C. Suffel Saturday, May 9 7:30 AM - 6:00 PM MAIUUETTE RANGE FIELD TRIP conducted by S. E. Gair of the U. S. Geological Survey. See the guidebook for details. Lunch will be provided en route. 8:00 AM A second field trip to the Republic Mine. 1:15 PM A second field trip to the Empire Mine. IV p.56 p.57 p.58 p.6O p.63 �AUTHORS AND TECHNICAL SESSION CHAIRNEN L, 0. BACON3 Professor of Geophysic8, Michigan Technological University, Hough ton, Michigan M. W. BARTLEY, General Mgr. Cliffs of Canada and Consulting Geologist, Port Arthur, Ontario M. R. BROCK, U.S.G.S., Denver, Colorado J. A. CAIN, Ass't. Professor of Geology, Western Reserve University, Cleveland, Ohio Madison, E. N. CAMERON, Professor of Geology, University of Wisconsin, Wisconsin. J. E. CASE, Geophysicist, U.S.G.S., Denver, Colorado Michigan V. L. DOANE, Research Engineer, Institute of Mineral Research, Technological University, Houghton, Michigan S. DUFFEL, Geologist, Geological Survey of Canada, Ottawa C. E. DUTTON, Geologist, U.S.G.S., Madison, Wisconsin Pine, Michigan C. 0. ENSIGN, Jr., Chief Geologist, Copper Range Co., White Columbus, Ohio G. FAURE, Ass't. Professor of Geology, Ohio State University, C. E. FRITTS, Geologist, U.S.G.S., Denver, Colorado J. E. GAIR, Geologist, U.S.G.S., Denver, Colorado of Minnesota Duluth J. C. GREEN, Ass't. Professor of Geology University Geological Survey, Duluth, Minnesota and Geologist, Minnesota W. E. HALL, U.S.G.S., Washington, D. C. A. V. HEYL, U.S.G.S., Beltsville, Maryland University, East W. 3. HINZE, Assoc. Professor of Geology, Michigan State Lansing, Michigan 3. M. HOSTERNAN, U.S.G.S., Beltaville, Maryland P. Massachusetts InM. }iURLEY, Department of Geology and Geophysics, W, C. KELLY, Professor C. KERMAN, Geophysicist, California Oil Co., New Orleans, Louisiana stitute of Technology, Cambridge, Massachusetts. of Geology, University of Michigan, Ann Arbor, Mich. V �P, A. LINDBERG, Geological Engineer, Anaconda American Brass Co. Ltd, Britannia Beach, British Columbia D. W. LINDGREN, President, Lindgren & Lehmann, Inc. 1ayzata, Minnesota R. E. LUBI(ER, Research Geologist, U. S. Bureau of Mines, Minneapolis, Minnesota A. S. MACLAREN, Geologist, Geophysics Division, Geological Survey of Canada, Ottaia J. T. MEGEL, Jr., Assoc. Professor of Geology, Wisconsin State College, Superior, Wisconsin V. C. MILNE, Geologist, Ontario Department of Mines, Toronto, Ontario W, W. MOORHOUSE, Professor of Geology, University of Toronto, Toronto, Ontario 3. M. NEILSON, Professor of Geological Engineering, Michigan Technological University, Houghton, Michigan T. H. NILSEN, Teaching Assistant & Graduate Student in Geology, University of Wisconsin, Madison, Wisconsin S. C. NORDENG, Assoc. Professor of Geology, Michigan Technological University, Houghton, Michigan R. PATENAUDE, Graduate Student & Research Assistant in Geology, University of Wisconsin, Madison, Wisconsin E. G. PYE, Resident Geologist, Ontario Dept. of Mines, Port Arthur, Ontario A. W. SCHILLINGER, Resident Geologist, Calumet & Hecla, Inc., Calumet, Mich. A. K. SNELGROVE, Professor and Head, Department of Geology and Geological Engineering, Michigan Technological University, Houghton, Michigan K. SPIROFF, Professor of Mineralogy, Michigan Technological University, Houghton, Michigan G. C. SUFFEL, Professor of Economic Geology, University of Western Ontario, London, Ontario 3. W. TRAMMELL, Staff Geologist, White Pine Copper Co., White Pine, Mich. C. VANVOORHIS, Graduate Student in Geophysics, Michigan Technological University, Roughton, Michigan L. W. WEIS, Ass't. Professor of Geology, Lawrence College, Appleton, Wiscons in. VI �51 ItO 04 027 4 046 AC -v r 320L1/ ,3 7/ Sc 30 / / 4 2? ci 1 / ( / // PAGE NUMBER& AREA INDEX 7,/ 7) I, �.AROMAGNETIC SURVEY OF THE MARQUETTE IRON RANGE1 REPUBLIC TROUGH1 AND ADJACENT REA. MICHIGAN J. E. Case Aeromagnetic surveys have been conducted by the U. S. Geological Survey over the Marquette iron range, Republic trough, Gwinn district, and adjacent areas on the Northern Peninsula of Michigan. The aeromagnetic surveys were flown at 500 feet above the ground along lines spaced at intervals of one-quarter mile in the western part of the area and at intervals ranging from one to three miles in the eastern part. The resulting aeromagnetic map is characterized by six groups of anomalies or anomaly patterns. (1) In the central, western, and southwestern parts of the area, iron-formation in the Animikie Series is shown by magnetic highs ranging from 2,000 to 25,000 gammas in amplitude. The pattern of magnetic highs over iron-formation generally outlines the west-trending synclinorium along the Marquette iron range, the northwest-trending Republic trough, and the belts of Animikie rocks south and west of the Republic trough. In a few places, especially in the Ish peming-Negaunee area, large magnetic lows are associated with Negaunee Iron-Formation, indicating that strong inverse remanent magnetization is Iron-formation in the Gwinn district does not yield recogdominant. Serpentinized peridotite in the (2) nizable aeromagnetic anomalies. pre—Animikie basement northwest of Ishpeming gives rise to an aeromagThe basement of gneiss and granite is (3) netic high of 7,000 gammas. characterized by a pattern of discontinuous highs and lows of low to moderate amplitude; the anomalies are generally less than 500 gammas. Intrusive greenstone in the basement gneiss is associated in some (4) places with distinct magnetic highs of moderate amplitude, 500 gammas, or more, but in other places it is apparently only weakly magnetic. Westward-trending reversely magnetized diabase dikes of Keweenawan (5) age are shown by prominent elongate magnetic lows of moderate to high amplitude. The lows are most abundant north of the Marquette iron range In the eastern part of the area, between (6) in T. 48, 49, and 50 N. Laughing Fish Point and Grand Portal Point, where Precambrian rocks are covered by as much as 2,000 feet of lower Paleozoic sedimentary rocks, large magnetic highs and lows with relatively flat magnetic gradients predominate. From the aeromagnetic data, vast areas can be eliminated as poHowever, tential sites for prospecting for magnetic iron-formation. the Gwinn dissome iron deposits of commercial grade, such as those in trict, may not be sufficiently magnetic to cause detectable aeromagnetic anomalies. Conversely, serpentinized peridotites can cause ano1 �maiies as large as those associated with some magnetic iron-formation. As expected, magnetic anomalies are generally of higher amplitude over magnetite-rich iron-formation than over hematite-rich iron-formation. Measurements of magnetic properties of iron-formation indicate that remanent magnetization may be of much greater importance than induced magnetization. Remanent magnetization must be evaluated if quantitative calculations based on aeromagnetic data are to be attempted. 2 �STRUCTURES IN THE EASTERN PART OF THE MARQUETTE SYNCLINORIUM Jacob E. Gair The U. S. Geological Survey and the Michigan Department of Conservation began in 1957 a cooperative program of remapping the Marquette district, ;using new 7 1/2-minute quadrangle sheets as base maps. The district comprises 12 such quadrangles and is about 600 square miles in area. Mapping has been completed in the Marquette and Sands quadrangles at the east end of the district and is now being done in the adjoining Negunee and Palmer quadrangles on the iest. About 125 square miles has been mapped to date. The westward—plunging Marquette synclinorium contains principally middle Precambrian metasedimentary rocks which formerly were considered Ruronian, but which are now placed in the Animikie Series by the U.S. The synclinorium is bordered by broad basement Geological Survey. areas of lower Precambrian mafic metavolcanic rocks and gneiss. The middle Precambrian (Animikie) formations in the mapped area are conformable Mesnard Quartzite, Kona Dolomite, and Wewe Slate separated by an erosional unconformity from an overlying conformable sequence of Ajibik Quartzite, Siaxno Slate, and Negaunee Iron-Formation. The most comprehensive result of the mapping has been a better definition of major structures in the eastern part of the synclinorium. The major synclinal axis in the Marquette and Sands quadrangles crosses the central parts of secs. 5 and 6, T. 47 N., R. 25 U. Considering the entire synclinorium as a first-order fold, the north limb is comparatively straight and only slightly affected by second—order folds, but along the south side a series of large westward-plunging second-order folds occurs en echelon to the southwest, between the eastern end of the synclinorium The noses of some of these folds are sliced and offset, and and Palmer. some limbs are thinned or eliminated by faults trending mainly westward or southwestward. The "outlier" of middle Precambrian rocks in the Palmer area has long been attributed to downfaulting from the main part of the synclinorium along such a fault, but the structural relationship of the rocks near Palmer to the overall fold pattern of the synclinorium remained obscure. Mapping northeast and east of Palmer shows the Palmer rocks to be a downfaulted segment of a large west-plunging syncline, at This synleast part of whose north limb was removed by the faulting. dine evidently is the southwesternmost in the series of second-order en echelon folds. The eastward-plunging syncline at the easterninost end of the synclinorium is an exception to the generally westward-plunging folds and 3 �reflects cross folding of Mesnard Quartzite and Kona Dolomite near the line between secs. 1 and 2, T. 47 N., R. 25 N. The major westward-trending faults are located in the principal Faults axial region of the synclinorium and along the south margin. in the latter area are indicated by brecciated and silicified zones, the local absence of lowest Animikie beds, and by southward dips of higher beds toward the basement. No such direct evidence of faulting is known aloog the north margin where, however, rocks close to the basal AnimIkie contact locally display strong vertical shearing and lineation. Furthermore, top directions in steeply north-dipping basement metavolcanic rocks point north, whereas tops in the vertical or steeply south-dipping Animikie rocks point south. Deep faulting beneath the north margin is postulated to explain both this unusual Itback_to_backtl relationship and the shearing. Cleavage in Animikie rocks in the eastern part of the synclinorium conforms closely to foliation and layering of probable early Precambrian age in basement rocks north and south of the synclinorium. On a regional scale the axis of the synclinorium also parallels the trend These facts of foliation-layering in the gneiss and the greenstone. controlled by suggest that the development of the synclinorium was earlier basement structures. 4 �STRATIGRAPHY OF ANIMIKIE (FORRLY HURONIAN) ROCKS EAST OF TEAL LAKE, NEGAUNEE, MICHIGAN Crawford E. Fritts 'ork done in cooperation with the Geological Survey Division of the Michigan Department of Conservation Detailed mapping in 1963 in and near the quartzite ridges known locally as the Makwa Hills (secs. 31, 32, 33, T. 48 N., R. 26 U.) east of Teal Lake, Negaunee, Michigan, has shed new light on at least two controversial aspects of the stratigraphy of rocks of Animikie (form(1) The Mesnard Quarterly Huronian) age in the Marquette District. zite, Mona Dolomite, and Wewe Slate of early Animikie age are distinctive mappable formations that represent a valid stratigraphic sequence. They are not "...more or less lateral equivalents of a single time unit..." as suggested by Tyler and Twenhofel (1952, p. 12). Facies changes within the Kona Dolomite, however, are recognized. (2) The Ajibik Quartzite, Siamo Slate, and Negaunee Iron-Formation of middle Animikie age represent a second sequence of time-stratigraphic units separated from underlying formations by an angular unconformity, The unconformity, which was confirmed during the recent mapping. first recognized by A. E. Seaman sometime prior to August 1904 (Van Hise and others, 1905, p. 90, 91), was not recognized by Tyler and Twenhofel. The controversy over the existence of the unconformity at the base of the Ajibik Quartzite arose mainly because Seaman's map of the Makwa Hills (Van Hise and Leith, 1911, p1. 19) shows parts of east-trending The quartzites in two distinct stratigraphic positions as Ajibik. southern unit, which is overlain conformably by the Siamo Slate, cuts across underlying formations with marked angular discordance along the southern side of the Makwa Hills, especially near the western edge of sec. 32 north of County Road 492 east of route U.S. 41. This quartzite still is recognized as Ajibik. On the other hand, the northern unit, which is exposed south of the Mesnard Quartzite in a roadcut on U.S. 41, is part of a sequence of interbedded slates and quartzites that conformably overlies the Mesnard. The conformable relationship near the roadcut was emphasized by Tyler and Twenhofel (1952, p. 24-26), but they continued to call the northern unit Ajibik. Apparently they overlooked the angular discordance displayed at the base of the typical Ajibik Quartzite in sec. 32. The quartzite exposed near U.S. 41 above the Mesnard now is recognized as the lowest of three quartzites interbedded with four slates above the Mesriard but overlain unconforinably by the Ajibik. Collectively, six of the seven interbedded slates and quartzites above the Mesnard are believed to be the near-shore equivalent of the Mona Dolomite. The uppermost slate is interpreted as 5 �Wewe (?) Slate (table 1), because there is no evidence that the uppermost slate was overlain by more rocks of Kona age before erosion in post-Wewe, pre-Ajibik time. The basin in cihich formations of early Animikie age in the Marquette District were deposited may not have extended much farther west or northwest than the present Makwa Hills. The Mesnard Quartzite pinches out less than half a mile west of the above-mentioned roadcut. This fact, together with the westward facies change in the Kona Dolomite from largely chemical sedimentary rocks to predominantly clastic sedimentary rocks, suggests that a shoreline existed in early Animikie It is not known, time near the western end of the present Makwa Hills. however, whether this shorline represented the edge of a major landmass or merely a local high on the basin floor in the vicinity of the Marquette District. References cited Tyler, S. A., and Twenhofel, W. H., 1952, Sedimentation and stratigraphy of the Huronian of Upper Michigan: Am. Jour. Sci., V. 250, no. 1 and 2, p. 1—27, 118—151. Van Hise, C. R., Adams, F. D., Bell, Robert, Lane, A. C., Leith, C.K., and Miller, W. G., 1905, Report of the special committee for the Lake Superior region: Jour. Geology, v. 13, no. 2, P. 89-104. Van Hise, C. R., and Leith, C. K., 1911, The geology of the Lake Superior region: U. S. Geol. Survey Mon. 52, 641 p. 6 �Table 1. Stratigraphic section in and near the Makwa Hills, Negaunee, Michigan. Age Formation Stratigraphic or lithologic unit Approximate Thickness (feet) Negaunee Iron—formation 1500-:- Iron—Formation Siamo Slate Slate with subordinate quartzite 1500—1800 6 w Ajibik Quartzite (vitreous) 75—150 __________________________________________________ Quartzite Slate with minor conglomerate 0—100 UNCONFORMITY Wewe(?) Slate Kona Dolomite (near-shore facies) 175-:- Slate Upper quartzite (vitreous to cherty) 50-175 Upper slate 50—150 Middle quartzite (vitreous to cherty) 100—200 Middle Slate 75-300 Lower quartzite (vitreous to cherty) 50-250 Lower slate 0-250 Quartzite 0—250 - Mesnard Quartzite (vitreous) Slate and thin-bedded quartzite 0-100 Quartz-pebble conglomerate 0-50 UNCONFORMITY - ".4 Metavolcanic and metasedimentary rocks, undivided 7 �T 47N T 48 N — .-- [000 0 1000 FEET MILE Underground cone workings IRON-FORMATION MAPPED WITH THE AID OF SUBSURFACE DATA OBTAINED FROM THE CLEVELAND-CLIFFS IRON COMPANY NEGAUNEE 1963 C. E. FRITTS BY OF THE NEGAUNEE 7/2' QUADRANGLE, MICHIGAN BEDROCK GEOLOGY OF THE SOUTHWESTERN PART L 0 ________ 0 -ii S Si 0 UNCONFORMITY Metovolcanic, metasedimentary, and intrusive rocks, undivided L Whte, Slate Sod, Conglomerate Quartzite Mesnard Quartzite H Ku Slate Kona Dolomite Ku, ,ndivided Upper quartzite Wh tn Upper slate Middle quartuite Whte, Middle slate Lower quartzite White, Lower slate Wewe (?) as, Conglomerotic slate UNCONFORMITY Quartz ite Ajibik Quortzite Siamo Slate Negaunee Iron--Formation Intrusive Metodiabase Li EXPLANATION a- cc 0 Lii cu cc co z �TREND SURFACE ANALYSIS OF TRACE ELENTS IN PEGNATITES IN MARQUETTE COUNTY, MICHIGAN Stephen C. Nordeng and A. K. Sneigrove This study is a test of the application of trend surface analysis to semi-quantitative spectrographic trace element analyses made on 33 samples from pegmatites from Marquette County. The and V. elements used were: Pb, Zn, Cr, Li, Ga, Ti, Sr, Ba, Ti, Be, V was found to be most closely associated with Ga, Ti with Be, Sr is most closely associated with Ba, Ti and Li with and Zn with Pb. Sr, and Cr with Li. The order of average intensity of trace elements from greatest to This ranking least is: Ti, Pb, V, Ga, Ba, Sr, Li, Cr, Be, Zn, and Ti. is similar to that of the abundance of the same elements in the lithosphere as a whole. Trend surfaces for the sample localities were run using the lithNumbers were ology of the country rock of the pegmatites as a model. assigned to Huronian, northern part of "Northern Complex', etc. A second model was based on the distance of the sample locality from the nearest Huronian contact on the assumption that this distance is related to depth beneath the surface at the time of pegmatite formation. Comparison of the trace element trend surfaces with the two models shows that depth of emplacement may have been a major controlling factor in the amount of a given trace element present. The greatest number of elements are present in pegmatites in the Lake Michigarmne and Big Bay areas. Used for purposes of prediction, the trend surfaces show that very large traces or greater quantities of Ti, Li, Sr, Ba, Ga, V, and Ti would have the most probability of occurring in pegmatites in the southeast part of the "Southern Complex" and in the northern part of the Zn, Pb, and Cr "Northern Complex," in the Big Bay-Huron Mountain area. Zn shows should decrease to the southeast in the "Southern Complex". Cr increases in the increase in the direction of Presque Isle Point. Lake Michigamitte and Big Bay areas. Pb increases away from the Dead River Basin in the "Northern Complex" and shows a slight decrease to the south in the "Southern Complex." Ba, Sr, Li, Cr, and Be increase, and the other elements decrease, in the Republic Area. 9 �This investigation is being extended to some 7,000 pieces of similar data available in Marquette and Baraga Counties from six other types of petrographic associations. These are described on the bases of geologic and geographic occurrence in Progress Report No. 10 of the Michigan GeoStrategic Minerals Investigations in Marquette and Barlogical Survey: aga Counties 1943 by A. K. Snelgrove, W. A. Seaman, and V. L. Ayres, 1944. 10 �SOME SEDIMENTARY INTERPRETATIONS OF GRANULE SIZE DISTRIBUTIONS IN THE LAKE SUPERIOR IRON FORNATIONS J. T. Mengel The size distribution of the iron-rich granules in the chert matrix of the thicker bedded types of Lake Superior iron formation were studied using standard sedimentary petrographic equipment and procedures to obtain objective data for the interpretation of sedimentary conditions. Size determinations were made on 250 randomly chosen grains in each of 108 thin sections selected to illustrate the granule texture clearly, to include as wide a range of grain sizes as possible, and to give an inclusive coverage of the Lake Superior iron formations. Limited materials representing the iron formations of the Beicher Islands and the Labrador Trough were measured for comparison and found to be similar to the American material. Granules occur in strata which exhibit graded bedding and cross bedding, and their association with chart and carbonate pebbles, f raginents of algal structures, oolites and, rarely, with detrital quartz, bear out their behavior as particulate detritus during sedimentation, and permit their interpretation as a special type of sand. The granules have a mean grain size toward the coarse end of the medium sand size range, moderately good to good sorting, a nearly symmetrical, mesokurtic, grain size distribution which is skewed toward an excess of fine material. Plots of mean size against standard deviation indicate that the granules accumulated in a tectonically stable environment which had a low rate of deposition and in which a considerable amount of re-working Oolites, associated with granules at a few horizons, have took place. approximately the same size parameters as do the granules, but typically are slightly coarser and better sorted. Moderately well sorted detrital quartz of fine to coarse sand If it is assumed that the granules and the size is locally present. quartz were deposited from the same current it is possible to estimate the specific gravity of the granules at the time of deposition, using the relationship: 0 A - 0B = 1/1.5 (Log2 - Log2D) where 0 is the mean grain size in phi units, D is the density of the 11 �mineral minus the density of water, and 1.5 is a constant for the sand size range (c.f. McIntyre, 1959, Jour. GeolQ, pp. 278—301.) Granule specific gravities appear to average about that of opal (i.e. about 2.0). The large grain size and low density of the granules would favor their selective transport and explain their sedimentary segregation from detrital quartz and aluminous material. Much additional quantitative work on granule size, shape, and packing parameters is needed to give a firm basis for chemical interpretations of the origin of iron formations. 12 �THE POSSIBLE ROLE OF LIFE IN THE FORMATION OF THE GUNFLINT IRON FORMATION. PORT ARTHUR REGION W. W. Moorhouse Organic remains have been recognized for many years in the Gunflint formation in Ontario and Minnesota. Examination of several hundred thin sections from various units of the Gunf lint has indicated that fossils and fossil-like structures are even more abundant than hitherto suspected, and has suggested that life may have had a profound effect on the conditions of sedimentation. The following structures have been recognized as organic or possibly organic in nature: Algal concretions, first recognized many years ago, and widely 1. distributed in the Port Arthur area. Anthraxolite, as seams and pockets, mostly associated with 2. algal structures; carbonaceous matter in argillites, tuffs, calcareous less convincing are brownish layers, and on stylolitic surfaces; (bituminous?) stains in chert and carbonate. Spherical structures, composed of carbonate, or carbonate 3. and greenalite, some of which are 30 to 40 microns in diameter (Fig. b), others up to .2 mm. (Fig. a), in calcareous layers and in shaly greenalite beds between lenses of taconite. A few have a complicated structure (Fig. c) or unusual forms (Fig. d), and are surely organic. Spherulitic structures (Fig. e), composed of chert ot car4. bonate, found in thinly bedded chert-carbonate rocks. Filaments, 20 to 30 microns wide, rarely preserved in greena5. lite (Fig. f) or taconites (Fig. g), may be algal filaments. Others, 1 to 3 microns thick, may represent bacterial chains or mycelia of fungi. Sponge spicules have been tentatively identified from one 6. outcrop of limestone in Port Arthur (Fig. i). Spots of greenalite in chert—greenalite granules, in one 7. specimen (Fig. k) are enclosed in carbonate showing a radiating structure (although the carbonate noi extinguishes as a unit). Possibly such structures are due to organisms. 13 �8. possibly A variety of larger, more complicated structures (Fig. j) organic. Having regard for the great age (possibly 2000 m.y.) and coinplicated replacement history of these rocks, the number of delicate structures preserved is surprising. It is tempting to assign a much more important role to the activity of organisms than has been the case hitherto. The following functions may have been performed by the life of the Animikie: As urged by some authorities for over forty years, organisms 1. may have been one of the most important agents of deposition of iron (iron bacteria, fungi, algae), of carbonate (algae and other primitive plants), and of silica. Organic growth and decay controlled the pH and Eh of the 2. waters in which deposition of iron, silica, and carbonate took place. Thus, at the same time, in adjacent environments, oxides, carbonates, silicates, and suiphides of iron were deposited, due to a variety of local environments, modulated by the proliferation or decay of organisms. Algal filaments and sea—weeds on the sea floor acted as 3. binders for the accumulating silicate, oxide, and carbonate granules. They stabilized these fragments in drifts or windrows, producing the characteristic wavy bedding of taconites. Abundant growth of phytoplankton in sheltered bays may have 4. produced stagnant areas where the thinly and evenly bedded chertcarbonate sections accumulated. The waxing and waning of these planktonic swamps with the seasons would conveniently explain the alternation of chert and carbonate layers. The growth of algal reefs may have brough added complica5. tion to local environments, by introducing barriers, and forming isolated lagoons. In conclusion, there are indications here of a population explosion of primitive plants, in particular those capable of precipThis may have been an important if not major factor in itating iron. making the Proterozoic the most prolific period of sedimentary iron ore deposition. Illustration: Organic or pseudo-organic structures from the Gunf lint iron formation. The horizontal bar beneath each sketch represents 0.1 mm. a) Spherical structure (carbonate) enclosed in greenalite. 14 �b) Spherical structure (carbonate), irnbedded in chert, in a carbonate layer. c) Complex "colony" of spherical structures. d) Spore—like structure, same thin-section as c. a) Spherulitic structure in chart, brecciated chert-carbonate rock. f) Filaments (with reproductive cyst?), in greenalite. g) Twisted filaments, outlined by greenalite, in chert; dark areas are parts of greenalite granules; from taconite. h) Filaments in algal chert; black spots are hematite dust. i) Suspected sponge spicules, from limestone. j) Spherical structure (organic?) of carbonate and greenalite(black). k) Chert—greenalite granule, containing circular spots of greenalite; some of the greenalite enclosed in carbonate showing radiating structure. 15 ��STRUCTURAL GEOLOGY OF THE SKIBI LAKE IRON PROPERTY NORTHWESTERN ONTARIO Paul A. Lindberg The Skibi Lake iron property, owned by Anaconda Iron Ore (Ontario) Ltd., is located in northwestern Ontario about 70 miles north of the town of Geraldton, Bands of Archean iron formation and schist outcrop intermittently along an eastwest strike length of over 20 miles and probably represent an eastward extension of the St. Joaeph Lake iron formations. These metasediments have been isoclinally folded and metamorphosed, faulted and secondarily folded, and intruded by granitic rocks, commonly pegmatite. According to Kindle (1931, Part IV, Vol. XL, Report on Ontario Dept. of Mines) they are included in the MarAnn. shall Lake series of Coutchiching (?) age. Potassium-argon age dating by Goldich et al (1961, Bull. 41, Minnesota Geol. Survey) revealed ages of 2.60 b.y. for the quartz biotite schist and 2.54 b.y. for the intruding peginatite. The bulk of the tectonic deformation of this area was completed following the widespread granitic intrusions of the Algoman orogeny. Late Precambrian diabase dikes cut the region causing local disruptions. The iron formations are magnetite and quartz-rich horizons and are in general of two related types. The most important is composed of banded magnetite and quartz with small amounts of amphibole and biotite, and commonly has a grade of 25-307. iron. The other type consists of cyclic layers of magnetite, schist and often quartz and ranges in grade from 10-30% iron. Garnet and mafic minerals are often concentrated at the interfaces between schist and iron formation. Any chert which may have been present initially is now completely recrystallized to quartz. The enclosing schist is composed of quartz, feldspars and biotite with lesser amounts of garnet and muscovite. Pre-pegmatite amphibolite dikes are sometimes encountered, and later intrusions were comprised of pegmatite, granite and granodiorite. The older horizon of iron formation was followed by ± 2000 feet of barren sediments before another horizon of iron was deposited under similar geologic conditions to the first. This latter formation is dominantly composed of a basal iron-bearing band and an upper higher grade band, separated by a layer of schist. The upper band varies from 10 to perhaps 80 feet in thickness across the district and constitutes the economically important strata from which the ore zones were later formed. Further deposition of barren sediments was followed by layers of volcanic rocks which now lie to the north. 17 �Large scale tectonic folding resulted from steady compression directed from the north and south. With very little apparent faulting a huge isoclinal fold developed much like the folds formed when a rug is The present orientation of the axial planes of these pushed together. folds is vertical at the west end of the district with a steady flattening towards the east where north dips as low as 200 are observed. At this point the apex of the isoclinal fold appears to have over-reached it's crustal support and a large fault block dropped several thousand feet forming the present Two Mile ore zone. Widespread faulting of the district was followed by pegmatitic intrusions along zones of weakness. The economically potential ore zones are the result of thickening of higher grade iron bands by isoclinal folding. The Briarcliffe ore zone is a tight Z—type fold where the limb of the regional isoclinal fold is in turn "isoclinally drag-folded" to yield widths of up to 500 feet of 25-30% iron. The Two Mile ore zone represents the fold nose of the regional isoclinal anticline. 18 �2 3 TWO MILE' o ORE ZONEf 5coIe " 4 SKETCH MAP OF SKIBI LAKE IRON PROPERTY SHOWING MAJOR STRUCTURAL ELEMENTS. FIGH TWO HORIZONS OF IRON FORMATION AND ENCLOSING SCHIST APPEAR TO BE ISOCLINALLY FOLDED ORE ZONES ARE THE RESULT OF FOLDING OF GOOD GRADE NARROW ACROSS THE PROPERTY. IRON FORMATION BANDS TO MANY TIMES THEIR ORIGINAL THICKNESSES. BRIARCLIFFE IS ON THE NORTH LIMB AND TWO MILE APPEARS TO BE THE DOWN-FAULTED ANTICLINAL NOSE. MAP SHOWING DETAIL OF EAS1 FIG. 2 (RIGHT) END OF BRIARCLIFFE ORE ZONE. THE UNFOLC ED IRON BAND AT® IS GREATLY INCREASED BY FOLDING IN THE ISOCLINAL ANTICLINOR- IUM" AT®. NOTE THE OBSERVED HABIT OF THE PEGMATITE DIKES AND SILLS TO WRAP — _\// fZ ..—.—'.-.— AROUND FOLD NOSES. '-'(/ ..••'___'i' ± ': ( i'. ., .j.. (,0' . FIG.3(LEFT) SKETCH FROM PHOTOGRAPH SHOWING NATURE OF ISOCLINALLY FOLDED IRON FORMATION AS SHOWN IN FIGURE 2. VIEW IS LOOKING TO THE NORTHEAST IN THE DIRECTION OF THE FOLD PLUNGES. FROM STRUCTURAL GEOLOGY OF THE SKIBI LAKE IRON PROPERTY, NORTHWESTERN ONTARIO' TENTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY, '9 964 PAUL A. LINOBERG �SOUTH NORTH PRE- PEGMATITE FAULT TRACES..\ —— -—— BELIEVED TO BE THE EASTWARD EXTENSION OF THE ISOCLINAL ANTICLINE AS SEEN IN THE BRIARCLIFFE AREA - I I I -,. -. OF SECONDARY — .— — —. — \ ZONE —.— -.---—-.—. •-• — 7 -- 2 ± 5000' \ FOLDING -,-- _5.rfoci r-_; --- - — - - - — -—— SCH 1ST . 0 1000' 0000 I I I \/s GNEISS , s,..SI — .5/ I., 3000 "GRANITIZED SCHIST" PEG M AT IT E Vert. £ .4orz. .5tIe 'O 2(.o40 VIEW LOOKING EAST SHOWING PROBABLE DEVELOPMENT OF THE TWO MILE ORE ZONE AS FIG. 4 THE DOWN-FAULTED ANTICLINALLY FOLDED IRON FORMATION FOLD NOSE. THE FAULT TRACE IS INTRUDED BY PEGMATITE DIKES PARALLEL TO DRAGGED SELVAGES OF IRON FORMATION. NOTE THE TWO AGES OF FOLDING: (I) ISOCLINAL FOLDING TRACEABLE FOR SCORES OF MILES WITH A PERSISTENT EASTERLY PLUNGE, (2) SECONDARY FOLDING OF LOCAL IMPORTANCE WHICH EXHIBITS OPEN FOLDS, WARPS AND CONTORTED BEDS. PEGMATITE INTRUSIOJ FOLLOWED THE LATTER. DIAGRAMATIC CROSS SECTION OF THE BRIARCLIFFE AREA SHOWING INFERRED AXIS OF MAJOR ISOCLINAL FOLD. TWO HORIZONS OF IRON FORMATION APPEAR TO BE PRESENT. THE OLDER IS LOWER IN GRADE, BUT GEOLOGICALLY SIMILAR TO THE YOUNGER, AND IS SEPARATED FROM IT STRATIGRAPHICALLY BY LESS THAN 2000. NOTE THE UNFOLDED SOUTHERLY LIMBS IN BOTH FIGURES AND THE ISOCLINALLY OVERFOLDED' NORTHERN ELEMENTS WHICH ARE OF ECONOMIC FIG 5 IMPORTANCE. FROM STRUCTURAL GEOLOGY OF THE SKIBI LAKE IRON PROPERTY, NORTHWESTERN ONTARIO", TENTH ANNUAL INSTITUTE ON LAKE SUPERIOR GEOLOGY, 20 1964 PAUL A. LINDBERG ��cut by granite from a granite granite in the Precambrian in dikes and pegmatites, which are probably offshoots Similar pluton in the southwestern part of the area. nearby Aurora-Niagara area is probably late middle age. The Florence area is divided into four blocks by faults of northwesterly trend whose southwest sides are relatively upthrown. The northernmost block is principally a northwestward-plunging major syndine containing the sequence from Michigamme Slate to post-Riverton strata, but most of the southwest limb is missing because of faulting and erosion. The synclinal structure, with widely deverging limbs, extends northwestward into and characterizes the geology of southern Iron County, Michigan; only Badwater Greenstone and Michigamme Slate continue southeastward along the syncline to its termination at a The adshort distance within southern Dickinson County, Michigan. jacent block on the southwest is mainly a vertical to steeply southward-dipping homocline of Michigamme Slate, but the west end is modified by southeastward-plunging folds of the Michigarnme to postRiverton sequence. This block is not known to continue northwestward beyond the Florence area; eastward to the end of the district it continues as a homocline of Michigamine and pre-Michiganime formations of middle Precambrian age. The next block is apparently also a homocline of Michigamme Slate with vertical to steep southerly inclination and top to the south; this block, like the one previously mentioned, exThe tends eastward only and also contains pre-Michigamme strata. southernmost block is underlain by the Quinnesec Formation of early Precambrian age, and the top is northward; this block extends eastward and in part probably northwestward. Metamorphism of the Precambrian rocks in the Florence area is mainly at chlorite grade along the central part of the plunging major Continuity syncline, and rises to garnet grade to north and south. of isograds appears to have been affected by faulting. 22 �GEOLOGY OF THE PINE RIVER (BREAIATER) QUARTZITE CONGLOMERATE AND THE KEYES LAKE QUARTZITE FLORENCE COUNTY, WISCONSIN T. H. Nilsen Setting: The Pine River (formerly Break'iater) and Keyes Lake units are informally designated members of the Michigamme Slate in the Baraga Group of the Animikie Series of the Middle Precambrian. They crop out in separate fault blocks as resistant northwest_southeast-trending Because they occur ridges in northeastern Florence County, Wisconsin. as steeply dipping homoclines, it is impossible to judge their original extent; also the lateral boundaries are generally vague due to lack of outcrop. They appear to be anomalous local lenticular quartzrich bodies within the more typical dark Michigamme slates, graywackes and basic volcanics. Pine River: The Pine River quartzite conglomerate crops out near the Pine River Reservoir five miles south of Florence and consists of a lower conglomerate, middle cross—stratified quartzite and pebbly quartzite, and an upper conglomerate, each of which thins to the northwest from a maximum total thickness of 600 feet to 150 feet in a distance of three miles. The underlying stratigraphic sequence indicates an upward gradational change from a reducing to an oxidizing depositional environment, i.e. from amphibolite and graphitic-pyritiC slate to grun— eritic quartz wacke to specularite-rich conglomerate. The strike of the homocline is northwest-southeast with a dip of about 700 to the southwest; the top of the unit everywhere faces southwest. The conglomerates consist of elongate pebbles of white and blue— gray recrystallized chert, interstratified chert and specularite, mosaic quartzite, and rounded strained vitreous quartz (probably vein quartz) in a fine granular quartzitic matrix that contains variable amounts of specularite, magnetite or martite, sericite and muscovite, biotite, chlorite, garnet, and locally grunerite and chloritoid. The middle unit is more quartzose and has small-scale inclined and festoon cross—strata that increase in abundance to the east • To the extreme northwest this 23 �unit is present in minor amounts as thin lenses of parallel-stratified quartzite within the conglomerate. Structural deformation along pairs of symmetrical shear planes produced elongation of pebbles parallel to the intersection of the shear planes, or the direction of tectonic elongation. Brief petrofabric study of orientation of quartz c-axes within pebbles suggests a deformationproduced fabric that has been considerably modified. Translation gliding within the quartz grains is suggested as the mechanism of elongation, with associated small faults, quartz-filled tension fractures, foliation Metaand lineation on the foliation also explained by the shear planes. morphism is at garnet grade, and it is suggested that it followed deformation, although a few strained and rolled garnets indicate some postKyanite was found in one thin section, metamorphic deformation as well. as well as coarse blades in quartz veins associated with coarsely crystalline specularite. Eighty percent of the 97 paleocurrent measurements indicate currents flowing toward the southeast quadrant. The postulated depositional environment was a shallow marine basin close to a local tectonically active source area that contributed coarse debris in two pulses, with transgression and regression of the sea possible contributing factors in the distribution of the sediment. Outcrops of apparently laterally equivalent chert breccias with magnetite and gruneritic iron formation to the southeast indicate a less energetic and possibly deeper water environment. Keyes Lake: The Keyes Lake quartzite crops out as a vertically-dipping, northwest-southeast striking homocline about two miles southwest of Florence. It is bounded on the north by a major fault and grades laterally into The iron—rich rocks of the Little Commonwealth area to the southeast. unit consists of horizontally—stratified quartzites, profusely cross— stratified quartzites and finer quartzose phyllites that can be traced for variable distances parallel to the strike. Thin persistent conglomeratic zones containing pebbles of rounded red and white vitreous vein quartz, fine quartzite and/or chert, and rare interstratified chert and specularite found in the northwest become finer, thinner, and apparently discontinous to the southeast. The quartzite consists of rounded vitreous quartz clasts suspended in a finer, granular quartz-sericite matrix with scattered zircons and magnetite—martite. Rare outcrops of units below this quartzite consist of hematitic quartzose phyllite and sericitic quattzose phyllite that grade upward into the quartzite. A variety of probably conformable rocks overlie it, such as chioritic-graphitic slate, chioritic slate with chert lenses or pebbles, and graywacke. Outcrop width narrows from 3000 feet to 250 feet in the southeast, The and the abundant cross-stratification has inclinations up to 650. 24 �cross-strata are of the inclined and festoon varieties with 89 percent of 144 paleocurrent measurements indicating current directions toward the southeast quadrant. Rare ripple markings confirm this pattern. The quartzite is extensively sheared, but the prominent foliation has a constant orientation regardless of the strike of the bedding. The unit has been subjected to chlorite grade metamorphism, but due to its composition the quartzite is not a good indicator of grade. The presence of chioritic, magnetitic, stilpnomelane-bearing rocks in one area overlying the quartzite that also contain grunerite and garnet suggests a local higher grade. This unit is postulated to have been deposited in a shallow marine basin that became somewhat shallower to the southeast before grading into deeper water deposits of the Little Commonwealth area, which contains a sedimentary breccia interpreted by Johnson (1958) to represent slumping along a surface of steep initial dip. Possibly the breccia is a result of intraforTnational Itripupfl in the postulated area of shallower water. Synthesis: The two quartzitic members were probably never coextensive, but may represent deposition in different areas along the same Precambrian coast line, or possibly under basically similar conditions at different Brief investigation of other quartzites in the Michigamme Slate times. indicates dissimilarity in composition, texture and stratigraphic features from the Keyes Lake and Pine River members. 25 ���( A ( A * A A, —f— j— *A A 'A/NY /VEAP S TEEPECCk x X LA kE X ON T,4 R/. AE'EA Kr 'vo -LEGE/VD - 0r '/ac,o/ 5/t,'i. D,r/,cri 0/ f)P/r( /P/ /ma/,/Q A.e05 0/ C0,ug/i-cj/rnj / Locci/,on 0/ ,4QP0O/I/ V14p - SCALL: /,'th '/ii'/ — KfY �HEMA TI r - . /,vG RA VEZ- A �AT VICTORIA VICTORIA GENERATING GENERATING STATION, LANDSLIDING AND AND RIVER EROSION AT STATION, COUNTY MICHIGAN ONTONAGON COUNTY. ONTONAGON MICHIGAN J. N. J. M•..Neilson Neilson River bank River bank erosion erosion and and massive massive slides slides of of Ontonagort Ontonagon clay clay long long have plagued the Upper Peninsula Power Company at its Victoria have plagued the Upper Peninsula Pover Company at its Victoria Generating Station Station on West Branch Generating on the the West Branch of of the the Ontonagon Ontonagon River River in in Ontonagon County, Michigan. generating Water ponded ponded by Victoria Dam Water by the the Victoria Dam is is conducted conducted to to the the generating approximately station turbines through a 6000-foot wood stave pipeline station turbines through a 6000-foot wood stave pipeline approximately Normally the ten feet feet in diameter. Normally ten the entire entire flow flow of of the the river river passes passes through the pipeline but during spring run—off, the excess through the pipeline but during spring run-off, the excess flow flow (est(est­ imated at at 10,000 10,000 c.f.s.) c.f.s.) is is diverted diverted through through the river channel. imated the river channel. Over Over run—off water water has period of of nearly 35 years, the the run-off has eroded eroded the the boulder, boulder, aa period sand, and and clay clay banks banks to point where where the sand, to aa point the power po~~er substation substation is is threatened. threatened. under Various river—training schemes and revettment systems are Various river-training schemes and revettment systems are under study study in an an effort effort to in to check further further erosion. erosion. Landsliding is Landsliding is aa problem problem of of more more immediate immediate concern. concern. AA particpartic­ of the ularly damaging slide occurred shortly after commencement ularly damaging slide occurred shortly after commencement of the The slide mass of river erosion erosion study. study. The slide involved involved aa mass of clay clay 250 250 feet feet wide 'Jide It effectually effectually dammed dammed the the tailrace and 1000 feet and feet long. long. It tailrace and and this this naturally resulted naturally resulted in in reduction reduction of of the the effective effective head head and and aa major major and and Several remedial measures costly curtailment costly curtailment in in power power output. output. Several remedial meaSures were were One solution was to considered. One solution was to restore restore the the tailrace tailrace section section by by digdig­ ging through the toe of the slide; another was to excavate a new ging through the toe of the slide; another WaS to excavate a new secsec­ Study of tion around around the tion the toe toe through through aa wooded wooded area. area. Study of air air photos photos and and had been been built examination of examination of the the site site revealed revealed that that the the power power station station had built It was decided to construct a new on an abandoned abandoned meander. meander. It waS decided to construct a new tailrace tailrace in the the bed bed of of the the old old meander meander channel channel with with a drag-line and in a drag-line and dozer dozer and and Although future this proved proved to be a this to be a simple simple and and practical practical remedy. remedy. Although future slides may may be be expected expected in in the the area, area, it is unlikely unlikely that slides it is that any any further further damage will will be damage be caused caused to to the the installation. installation. 30 30 �ORIGIN OF THE TIGERTON ANORTHOSITE Leonard W. Weis occupies about about 200 200 square square miles miles in in western western anorthosite occupies The Tigerton ariorthosite It is Shawano County, Wisconsin. It is a hornblende anorthosite anorthosite of of igneous igneous origin. The plagioclase is is generally high andesine or low low labradorite, labradorite, with occasional grains low andesine or high labradorite. labradorite. Accessory Accessory minmin­ grains low erals include hornblende, magnetite, magnetite, ilmenite, erals include hornblende, ilmenite, sphene, chlorite, biotite, biotite, In places places the rock is is crushed, crushed, in places it shows a pyroxene, epidote. epidote. In the rock It is is surrounded surrounded and and cut cut by the Bowler granite non-diagnostic foliation. foliation. It which is is considered an an independent independent unit. unit. Structurally, the the anorthosite anorthosite occurs as at least occurs least two two roof roof pendants pendants in in the the granite. granite. The country country rock rock was probably a series of metasediments, but invaded by the the anorthosite was the evidence is the is scanty. scanty. Igneous origin for Igneous for the the anorthosite is stated, inter inter alia, alia, because of the optical character of the plagioclase, the characteristics of of the optical of the plagioclase, of the the ore minerals, the textural relations, and several minor features. are minerals, the relations, features. PostPost­ formational metamorphism metamorphism certainly occurred, formational occurred, explaining at least least in in part The possibility of the formation of an inde­ inde the crushing and foliation. the and foliation. The possibility of the formation of an pendent anorthosite magma has been demonstrated demonstrated by Yoder Yoder && Tilley Tilley (1962) (1962) and the the Tigerton anorthosite is and is an example of the emplacement of such aa magma. 31 31 ��BA1AGA COUNTY. COUNTY, MICHIGAN DEPOSITS, BARAGA THE ARVON t:'HE ARVON SLATE DEPOSITS. Kiril Spiroff In the the Arvon Arvon slate slate quarry quarry area) area, the the stratigraphic In stratigraphic succession is pure, massive, massive, vitreous quartzite, as quartzite, probably probably Ajibik, Ajibik, as follous: follois: aa pure, which is is the the oldest oldest rock rock exposed; exposed; a thin thin quartz quartz con3lcrnerate; con3l8merate; aa reddish to black quartzite; aa thin thin cherty cherty carbonate carbonate member; menber; gray gray to variegated slate; slate; black satiny slate, to slate, and, and, lastly, lastly, pyritic black slate. 8 late. Three small pits pits in the uere worked from Three the black satiny slate ~7ere from 1872 to to 1890) 1890, during during which time time 50,000 squares squares of roofing slate 1872 worth 188,000 188,000 iere uere produced. produced. These These deposits deposits are are probably probably not not of of commercial value today. today. 33 33 �MICHIGAN TEACHING MINERALOGY MINERALOGY MICHIGAN TECH'S TECH'SMETHOD THO OFOFTEACHING Kiril Kiril Spiroff Spiroff The technique ~f identification which which is is taught taught The technique of megascopic megascopic mineral mineral identification at Michigan Tech differs fr~m that of most schools in that it puts greater at Michigan Tech differs from that of most schools in that it puts greater stress on the use of cleavage and/or crystal form whenever these features stre&s on the use of cleavage and/or crystal form whenever these features are in the the unknown unknown mineral. mineral. are present in Michigan Tech's system system starts starts with with the the placing placing of of the the unknown unknown min­ Michigan Tech's mineral into one of three classes as shown in Plate 1. This shows that the the eral into one of three classes as shown in Plate 1. This shows that specimen Can be: be: specimen can 1. A cleavage fragxnent,or fragment,or 1. A cleavage 2. A or 2. A crystal. crystal, or 3. 3. Massive, that is, is, fine—grained fine-grained so so that that neither neither crystals crystals nor n~r Massive, that cleavages can be be observed. observed. cleavages can 1. Cleavage Fra_gments Fragments 1. Cleavage Cleavage a mineral possesses due due to to its its atomic atomic arrangearrange­ Cleavage is is aa property property a mineral possesses ment and is recognized by the greater amount of light which is reflected ment and is recognized by the greater amount of light which is reflected area from from cleavage cleavage planes. planes. Cleavage Cleavage may may be considered considered from from per unit area three aspects: number, perfection, and angular relations (Plate 2). In three aspects: number, perfection, and angular relatior1s (Plate 2). In number there can Can be one, two, two, three, three, four four or six separate separate cleavages. cleavages. In types, from perfect+toto distinct -. In perfection perfection we we recognize recognize seven types, perfect-Egistinct_. 6 0 0 In angular relations we deal with and measure only 60 , 75 and 90 In angular relations we deal and and 90 75 angles. The student starts starts with large simple simple fragments fragments and and works works toward toward The student with large smaller, less less perfect fragments. fragments. , The is held held in in the the right right hand hand and and turned turned until until aa light light The specimen is flash from from aa mineral mineral cleavage cleavage plane plane is is observed. observed. Then Then the the specimen specimen is is rotated to to the the next flash flash by by using using the the wrist, not the the fingers. fingers. The The wrist, not amount is noted as as well as the the cleavage cleavage perfection. perfection. If this amount of rotation is veil as If this is the eyes eyes will observe the patterns produced produced by by the the is done done objectively, objectively, the number of relations. After After practice, practice, the the of cleavages cleavages and their angular relations. angles 60°, 75°, 75 0 , and and 90° 90 0 can can be be easily easily distinguished. distinguished. angles 600, At this this point, point, the the identity identity of of many many minerals minerals will will have have been been estabestab­ lished. For example, a mineral showing showing four four perfect perfect cleavages cleavages and and having having example, a vitreous luster aa vitreous luster is is Fluorite. 2. 2. Crystals If shows crystal crystal faces, faces, it it is is pigeon—holed pigeon-holed into into the the If the the specimen shows system by the the study study of of the the geometry geometry of of those those faces. faces. proper crystal system The first studied with the the unaided eye eye or or with with The unknown crystal is first the hand lens. the lens. The planes planes of of the the observed observed crystal crystal faces, faces, if if they they are are incomplete, are extended extended mentally mentally until until they they intersect intersect so so that that the the corn— com­ incomplete, are 34 �crystal form form is is visualized. visualized. plete crystal The and rotated around around an an imaginary imaginary The crystal is is held held vertically and axis and the axis the angles of repetition repetition are are observed0 observed. If If the the faces faces are are rere­ peated every 90°or 90 0 0r four times during one revolution, revolution, the the crystal pospos­ sesses a four—fold sesses four-fold symmetry. symmetry. If the crystal itself every If the crystal face face repeats repeats itself every 600, or six 60°, six times times during during aa complete co~plete revolution, revolution, it it has has aa six—fold six-fold symmetry, If the crystal face symmetry. face repeats repeats itself itself every every 1200, 120°, or three or three times during aa complete revolution, revolution, it it has has aa three—fold three-fold symmetry. symmetry. times these symmetries, symmetries, minerals Can be into the the various various Using Using these minerals can be classified into systems shown in in Plate Plate 3. 3. This takes takes care of one—half one-half of of the the systems, systems, but all all crystals crystals do do not possess aa four, four, three three or or six—fold six-fold symmetry. symmetry. In In crystals crystals which which lack lack these is sought. sought. A prism consists consists of of two two or or more more these symmetries, symmetries, a prism is A prism planes extended, will intersect intersect and have the the same Same angular angular planes which, which, if extended, relationship to relaticnship to some some other other plane. plane. The prism prism is is held held vertically, vertically, and and by using using the the principles principles shown shown in in Plate Plate 4, 4, it it can Can be be classified classified into into the the by proper system. If the complete If the complete crystal form cannot be visualized and classified in the next is to to construct construct an accurate picture of aa in this this way, way, the next step step is the unknown unkno'Jn mineral by by working from from theoretical theoretical axes axes perfect crystal of the and Miller indices. and indices. Orthographic Orthographic and and Clinographic Clinographic projections projections are are used. used. The unknown crystal is sketched as architects architects sketch sketch aa building: building: by by dra'Jing view. A side view view is is also also helpful. helpful. After After the the dra'iing aa plan plan and and front view, A side proper system system has has been determined determined and and an an accurate accurate sketch sketch has has been been drawn, forms characteristic of the the system can be be studied. studied. drawn, the forms advanced stage stage in in the the course, course, atomic atomic arrangement arrangement is is disdis· At aa more advanced cussed and the the use of of XX rays rays is is expained. expained. 3. 3. Massive Specime.a Specime~~ If the unknown mineral is is megascopically massive, the the usual usual If the methods of identification identification are are used used as as outlined outlined in in Plate Plate 5. 5. The basic System is is to to basic objective of Michigan Tech's Tech's Mineralogical System train the student to observe the physical properties of minerals in in aa train the student to systematic cleavages and and crystal forms, forms, and and to to systematic way, way, perticularly their cleavages seen on on paper in in aa neat neat and and orderly orderly fashion. fashion. When put what has been seen this the mineral is is usually aa this has has been done, done, the identification of the simple matter of correlating his simple his findings findings with any any standard standard mineralogy text or mineral table. table. 35 35 �I 22 CRYSTAL CRYSTAL I CLEAVAGE CLEAVAGE FRAGMENT FRAGMENT 33 NEITHER NEITHE R MASSIVE MASSIVE PLATE I C~PLATEI CLEAVAGE CLEAVAGE I,L2,3,4, 2, 3, 4, 6. 6. I,I, NUMBER 2,PERFECTION 2, PERFECTION PERF 4+ ++ PERF ++ PERF PERF PERF DIST ++ DIST DIST DfST DIST - MUSCOVITE MUSCOVITE GRAPHITE CALCITE GAL E NA GALENA ORTHOCLASE'" ENARGITE ORTHOCLASE"C" ENARG ITE ORTHOCLASE "S" "B" COSAlTITE COBALTITE ORTHOCLASE WERNERITE APATITE CASSITERITE 3, ANGULAR ANGULAR RELATIONS RELATIONS PATTERNS I 22 3 44 6 PYRITE ARSENOPYR I TE ARSENOPYRITE TANTALITE TANTAllTE 750 6O 60~ 75°.. 9Qo 90~ PRODUCED PRODUCED PLATY PLATY FIBROUS FISROUS~~? ~ A BRICKS BRICKS T/7./ HOMB RMAi?f PLATE PLATE 22 �____ CRYSTALLOGRAPHY CRYSTALLOGRAPHY 3 3 ATOMS ATOMS 2 2 AXIS I PLANES PL ANES I HAND LENSE HAND LENSE X-RAY EQUIPMENT X-RAY EQUIPMENT DRAWING DRAWING MUST SKETCH MUST SKETCH CRYSTAL CRYSTAL TETRAGONAL TETRAGONAL ONE ONLY ONLY FOUR-FOLD ONE FOUR- FOLD:J SYMMETRY SYMMETRY HEXAGONAL HEXA GONAl ONEONLY ONLYSIXSIX-FOLD ONE FOLD 00 SYMMETRY SYMMETRY TRIGONAL TRI GONAl ONE ONLY ONLY THREE-FOLD ONE A SYMMETRY 6 SYMMETRY © ISOMETRiC ISOMETRIC MORE THAN ONE MORE ONE FOUR-FOLD SYMMETRY FOUR-FOLD SYMMETRY MORE THAN THREE-FOLD SYMMETRY SYMMETRY MORE THAN ONE ONE THREE-FOLD COMBINATION OF OF FOUR COMBINATION FOUR AND AND THREE THREE FOLD FOLD SYMME SYMMETRY PLATE PLATE 33 @ �IN CRYSTALS WHICHLACK LACK0 ElD.A 0 SYMMETRY IN CRYSTALS WHICH SYMMETRY FOR AA PRISM FOR PRISM LOOK MORE PLANES A PRISM PRISM IS TWO OR OR MORE PLANES IF IF EXTENDED IS TWO WILL SAME ANGULAR AND HAVE AND HAVE THE THE SAME ANGULAR INTERSECT RELATIONSHIP TO SOME TO SOME OTHER OTHER HOLD PRISM PLANE. VERTICAL VERTICAL ORTHORHOMBIC ACROSS TOP IS IS STRAIGHT e @@ MONO CLINIC MONOCLINIC TOP ill SLANTS m TRICLINIC TRIC LINIC TOP IS IS CROOKED PLATE 4 PLATE 4 m �MASSIVE MASSIVE LACKS CLEAVAGE LACKS CLEAVAGE OR OR ITS ITS TOO TOO FINE FINE TO TO SEE SEE CRYSTALCRYSTAL­ LINE HABIT LUSTER=APPEARANCE L USTE R =APPEARANCEOFOFMINERAL MINERAL SURFACE SURFACE IN IN LIGHT CAUSED LIGHT CAUSED BY BY ABSORPTION ABSORPTION AND AND REFLECTED REFRACTION MINERAL TYPE VITREOUS RESINOUS RESINOUS ADAMANTINE N N WATER CORUNDUM SPHALERITE COPPER I.1.33 33 1.77 2.5 METALLIC METALLIC HARDNESS = =MINERALS HARDNESS MINERALS ABILITY ABILITY TO TO SCRATCH SOME OTHER STUDENT EROSION----- KNIFE-—STUDENT EROSION KNIFE --- ABRAID ABRAID OR OR SUBSTANCE FEEL --— FEEL --- SOUND--SOUND--­ SPECIFIC GRAVITY= MINERALS SPECIFIC GRAVITY = MINERALSWEIGHT WEIGHT IN AIR IN AIR AN EQUAL COMPAIREDTO TO THE THE WEIGHT COMPAIRED WEIGHT OF OF AN EQUAL VOLUME VOLUME OF OF LUSTER OF OF THE THE MINERALS. WATER. USUALLY ASSOCIATE WATER. USUALLY ASSOCIATE GRAVITY GRAVITY WITH WITH THE THE LUSTER MINERALS. COLOR IFIF IT HAS IT HAS AA DEFINITE DEFINITE AST TA ST E E OF SOLUBLE MINERALS. OF SOLUBLE MINERALS. STREAK ODOR FINE FINE POWDER. POWDER. WHEN SCRATCHED WHEN SCRATCHED FRACTURE AND TENACITY CONCHOIDAL. SECTILE. ELASTIC. FRACTURE AND TENACITY CONCHOIDAL.SECTILE.ELASTIC. CHEMICALS HCL MAGNETITE PYRRHOTITE. MAGNETISM MAGNETITE PYRRHOTITE. HCL ASSOCIATION II "KIN FOLKS' IIKIN FOLKS PRESSURE TEMPERATURE PRESSURE TEMPERATURE TIME TIME PLATE 55 PLATE �PETROGRAPHIC ANALYSIS ANALYSIS OF PETROGRAPHIC OF MESABI MESABINON1IAGNETIC NONMAGNETIC TACONITE TACONITE USING THE THE POINT COUNTER R. R. E. E. Lubker Lubker this study was the application of the the pointpoint­ The objective of this counting method to to samples samples of of West lvest Mesabi Mesabi noninagnetic nonmagnetic taconites taconites for for were a quantitative mineral analysis. quantititive analysis. Samples Samples used used \'1ere a screen screen fraction fraction of of each of 159 composites, which were taken in a sampling area extending each of 159 composites, 'tlhich Here area Samples were were split for 50 30 miles along for along the the range. range. Samples split in in aa microsplitter, microsplitter, briquetted with aa cold-setting cold-setting plastic, plastic, polished polished on briquet ted with on aa leather leather lap lap with \7ith chromium oxide, and counted with an electronic point counter. chromium OXide, and ~.,ith electronic counter. Weight-percent of Weight-percent of each each mineral mineral was was calculated calculated from from the the modal modal analysis by using a standardized density value, and the iron-bearing analysis by using a value, iron-bearing minerals ~'lere were multiplied by their minerals their respective respective iron iron factors. factors. For For each each sample, these calculated iron values were added to give total count Fe. F. sample, these calculated iron values were added to give total count The count analysis was compared with the chemical Fe analysis and an The count analysis was compared with the chemical Fe analysis and an arbitrary limit limit of of 2~ 2 percent arbitrary percent difference difference of of count count Fe Fe from from chemical chemical Fe Fe Ninety-one çercent of the samples fell within was established. Ninety-one rercent of the samples fell within this Has this limit; the the failure failure of of those which did did not, not, after after several several recounts, limit; those l;hich recounts, can can be attributed to adverse physical characteristics and mnera1 be attributed to adverse physical characteristics and mineral assoasso­ cia t ion. ciation. 40 40 �~PARATION PREPARATION MINERAL SPECIMENS SPECIMENS OF MINERAL FOR ELECTRON ELECTRON MICROSCOPY MICROSCOPY Virginia Doane Virginia L.L.Doane In the for examination by electron the preparation preparation of of specimen mounts mounts for microscopy, two microscopy, t~o limitations are imposed, imposed, due to to the the fact fact that that the the mass inof the electron electron is is so so small small that that its its movement movement can canbebeimpeded impededbybyinf infin­ itesimal limitations are (1) (1) the the specimen specimen itesimal amounts amountS of matter. These limitations thin and (2) (2) the the examination examination must be be conducted conducted in in an an ulul­ must be ultra thin tra high vacuum. vacuum. With these limitations l~ith limitations in in mind, four four classes classes of of specimen specimen mounts mounts (1) suspensions suspensions of microscopic and can be examined: (1) and submicroscopic submicroscopic solids, (2) ultra thin sections, (3) solids, (2) ultra thin sections, (3) surface films films and deposits and and (4) replic~s replicas ~hich which reproduce the surface (4) surface structure. structure. This paper describes the This the preparation of of these these four four types types of of specspec­ imen mounto mounts and and is is illustrated by the electron microscopic study of imen nuclei formed by by the the direct direct reduction reduction of of hematite. hematite. 41 41 �ALTERED SPODUMENE SPODUMENEOFOFTHE THELITHIUM LITHIUM PEGMATITE PEGNATITE DEPOSITS ALTERED AREA, ONTARIO OF THE THE GEORGIA GEORGIA LAKE LAKE AREA. mrrARIO E. G. G. pye Pye and and V. V. G. G. Milne Mime E. Because of alteration, alteration, some of the spodumene in certain lithium lithium pegniatite bodies of Archean Archeart age age in in the the Georgia Georgia Lake Lake area has low pegmatite bodies of low lithia lithia In several cases it and high iron contents and is not marketable. and and is not marketable. it dede­ tracts appreciably from the values values of the deposits containing it and tracts and is of considerable economic significance, is significance. There are two types of altered altered In one, the spodumene has been altered to a granular—texured spodumene. one, the granular-texured aggregate of of muscovite, muscovite, in the other, other, it has has been sericitized and renaggregate ren­ dered dark green green to to black. black. l4uscovitized spodumene spodumene is is associated associated with with cogenetic cogenetic aplite aplite and and Muscovitized muscovite—quartz veins and replacement units of saccaroidal albite muscovite-quartz saccaroidal albite or or Sericitized spodumene post— of muscovite-albite intergrowths. intergrowths. Sericitized spodumene is is post­ pegniatite in in age age and and is is believed believed to to be be related related in in space space and and time time to pegmatite Proterozoic diabase intrusives. intrusives. 42 42 �Chemical Analyses Analyaes of of Spodumene Spdumene Crystals Chemical Crystals Georgia Lake Georgia Lake Area Area (Analyses Nos. Nos. 1-5 1-5 by by the Laboratories Branch, (Analyses the Laboratories Branch, Ontario Ontario Department of Mines) Department of Mines) !I I I No.1 I ! A1203 A1 20 3 No.2 Altered Altered Spoduinenesi Spodumenesl No.3 No.3 No.4 No.4 No.5 No.5 Muscovites Muscovites II No.6 No.6 No.7 No.7 1 45.21 45.21 48.76 48.76 i , Si02 Si0 2 \ Unaltered Spodumenes i 60.85 60.85 62.70 I 62.70 i 61.44 61.44 48.84 48.84 27.60 27.27 I I 29.06 29.78 29.78 28.23 28.23 I 33.40 33.40 29.91 29.91 1.53 1.22 1.22 1.50 1.50 4.59 4.59 2.78 2.78 4.24 4.24 2.00 2.00 0.41 0.41 - 0.33 0.33 1.58 1.58 2.63 2.63 i i 49.57 49.57 I I Fe203 Fe203 0.29 0.29 FeO 0.44 0.31 0.33 2.19 2.19 1.56 1.56 CaO - 0.34 0.28 0.28 - 0.40 0.40 MgO 0.32 0.22 0.22 0.16 0.16 .00 2.73 2.73 Li203 0 Li 2 3 6.62 5,33 5.33 5.63 5.63 0.43 0.43 0.15 0.15 - K20 KzO 0.23 0.16 0.16 0.33 0.33 8.99 8.99 6.50 6.50 10.71 10.71 6.83 6.83 Na20 Na 0 2 H20 O H2 0.24 0.24 0.17 0.17 0.12 0.12 0.20 0.20 0.16 0.16 0.42 0.42 2.31 2.31 - — 3.95 3.95 4.60 4.60 ­- .- 0.94 0.94 - 5,26 5.26 - — i I- F F - L.O.I. L.O.I. I Totals I 97.79 I I No. 1. No.1. No. 2. No.2. No. 3. No.3. No. No. 4. 4~ No. 5. No.5. No. 6. No.6. No. 7. No.7. ~ -•••— ••— • 1.20 1.20 I- - I i . . -- I ! 0.65 0.65 0.70 5.73 99.27 99.27 100.66 100.66 i •! — I 98.68 98.68 l I , — — I - I 98.95 98.95 deposit, Jean No. 11 deposit, Jean Lake Lake Lithium Lithium Mines Mines zone, Nania Creek Mines North zone, Nama Creek Mines Ltd. Ltd. zone, Nama Nama Creek North zone, Creek Mines Mines Ltd. Ltd. 1 deposit, Jean Lake No. 1 deposit, Jean Lake Lithium Lithium Mines Mines Mines Ltd. zone, Mama North zone, Nama Creek Mines Ltd. No. 11 Muscovite No. 11 (Dana, (Dana, 1909). 1909). Muscovite No. Muscovite No. 16 16 (Dana, (Dana, 1909). 1909). 43 43 Ltde Ltd. Ltd. Ltd. ­ - - — 00e99 (aOO.99 : 1 I - — ­ ­ — 100.02 100.02 �VERTICAL DYKE DYIE NO. NO. I I LUN ECHO LUN ECHO I I I I II I ~ 11 I I LEGEND f////J I.§:'>...'l§§l DIABASE DIABASE [LU] METASEDIMENTS METASEDIMENTS [[[[] LITHIUM LITHIUM , I"::,"~::::;' I I )~";\ ~III ,z~ :0.~2~1 I~ 21.0 . " , n'''j ~~~~ Il II: \L 1,IL1J 1,1: J 1'1 ~~ O<.J..'1 2.57 % 21.0 feetL;2 ~~,. L-314 L-31B I I I I I I I _0.42% "'.J L-'" a.57% Li200 r-- L-3IA I LIMITED MINES GOLD L-I S.E. S.E. 4900 4900NN SECTION SECTION _0 2 LI 0 I (150/, S I pod I I' ° (20 ~II I II 29 1 • I N.W. I I I 1 I S~ . I (1501. I I 545 .. " I I 120 N.W. '1° feet III 2~ 1°1 • Spod.) Jli , '/ . PEGMATITE PEGMATITE SYMBOLS SYMBOLS CORE CORE 0 o L-I L-I SAMPLE SAMPLE DIAMOND DIAMOND QRILL QRILL GEOLOGICAL -- -- -- GEOLOGICAL HOLE BOUNDARY WITH WITH NUMBER NUMBER (ASSUMED) SCALE SCALE —— 00 1__ 40 '0 OF OF 40 40 I I FEET FEET 80 80 I I 20 120 I I -­ �______ NORTHWEST NORTHWEST _ SOUTHEAST I~ -- ------,'''' IV­ t I':',' --4------------'<-----~""-, I~ ,".; ~- I~ I) "v l'r '---~---------~-------'.., 1-') \ "'.' ~) :-----~--------~._________h, )-~, "''''''' _---_....... L 120 (20 0/0) % '\ J.... 1'\;-_ II ',\, , ,')' _~~''-,..1., ~), I 4 . 0 FEE T " ~J lJ ~--------___;,... ," ,II (,I , ,- ~-- I' ,".; ," ''.I ~~ _ _ _ _ _ _- - - - - - l l [ _ _ - - - - - - - ,"ty-( ,-, J) ~',,' (i ,''' 1'\.,'-- I)' 1......." -'_ _ I~ :;'::; IS~, '! " ::: <.,'1')') , _ "" _ _ _ _ _ _ _~------,'v-I--.:.-~,~) "I '"'J V "r __, _ ........' ,\' I,J-!'..r- /-',- '" ,'\r "x...­ \".;-­ _ _ _ _~_-----___,___--__:__~,:~"'~~,., r 4 '''i -- ~.______-----~I~t _ T- _ ,,", ' \ N,., " ~--_____,,~I"-t--'"'-I~--------".----f'\,.'------ --\- ') "-v !'I '" (~-:---...n; l'-...v tI-,) ,v ~___\'___-----------":~--" " I) ,'\.'N ''\., ""- . ; - - - - - ­ " '" ) ''\., ,-----_~-------------ll[___...,' - '''-:t':--,I.J':-------''',~----" I ........ " 1,1 '''-..',., I'\., 't------..:~---- ,'I N _ _- - - - - ­ 1 _ _----\-_L'20 (15 0/0) __ ~~~:j} I ~~-~~--- " "'-r--:,\,"', ~ 10 ~~: FEET , ~? t:::;": ---\- ,0__ \' ,~, :; --------'<-----,~I;), _ / NC-36 I~' -,:,'-~-----I'f-------- ","\( rI ",'" -----'r---:::--"-:-l"i'--~\,___--:--------­ ,~ II ,~.... r --f : , //. _-/. - /. _ /--/ __/.. /_." , ,y ','~ / -- .. ,"..; ' , PEG MATI TE P EGMATITE _ ""1 " "w'-----­ I"I - - I, -,." ~; ,~' I'" ~;----,~-," (] ," "" ~) ) ,l\--~' I~ .... ~~' I ~ ~ ", --;)~'" ~ METASEDfMENTS METASEDFMENTS _ ~ N _ _ (_"'--\--;-- . . . . -~ ''\. I~ " :>-.'-1 "--,,,-, ,~ ,::. II II 1"1, ~~ " - - - - - - < - __ 1'1 ,\ ,. II "r ,',< ~) --------".-" '-' I' ~' ,;' ,,-'<------­ I " "-'- D BAS E DII AABASE o /.7 " '\.' LEGEND " ,')-----­ ," ~~~'r-;---- ' - - - - - - \ --,'+-,\"---­ S S SY YM MB B 00 L S --- Ij ,) L.-- ~--- -- AI "'-' ' ~ .. lJ ----,'\ / ,~) ,)---------..:1.--- 41 - - - - - - - - ­ - /"-'2. ' I I . 0 FEE T / ---l\,___--IJ U 0/0) ~o,;'~-,~:?/~.~·-.l::~;:'--b~,:-------_. I Q/o L ' 2 0 (20 / N ....' I I - - - - \ - - I'-,'.....; _ I l , KI t' A ( \'~').- ,", ,", - N C - 49-t\" ' - " ,\., , '"-I- N - - ­ N --1\0-.., - - ­ - - , '" G E 0 LOG ALB 0 U N DAR Y , ''\..,lJ, S S'lJ M E D GEOLOGAL BOUNDARY,' ASSUMED NC-36 1DIAMOND NC-36 DIAMOND DRILL DRILL HOLE HOLE WITH WITH NUMBER NUMBER SPODUMENE ESTIMATED ((20%) 2 0 0/0) S POD U MEN E CONTENTS CON TEN TIE S TIM ATE D , 80 80 SCALE OF SCALE OF FEET FEET o0 80 80 160 160 240 240 T Fig. ? ��in the the outer outer fringe fringe of of the aureole and migration of the in the aureole the elements toward the ore zone. the zone. However, HOvlever) the the proportionate volumes volumea and and contents of the the with those those of of th8 the inner alter~tion alteration aureole leached zone as c.Dmpared c)mpared with aureole and and ore zone zone suggest suggest that that much much of of the the aluminum, aluminum, irou, irci silica, ore silica) titanium, titanium) and and by the the ore-bearing ore-bearing solutiono solution3 from from sources sources other manganese were ~lere ad-1ed ad1ed by than leaehed outer part. than the the narrow leached Other studies in in progress of of samples samples from from the the Thompson-Teniperly Thompson-Temperly include: mine include: (1) (1) X-ray diffraction analyses which indicate indicate that that an an abundant abundant gray cobaltian iron iron sulfide sulfide from from the the mine is is pyrite pyrite with ~lith micro-intergrowths of probable cobaltite. (2) (2) Calcite grew in four successive crystal habits; scalenohedral scalenohedral forms predominate predominate in stages, rhombohedral forms forms in earlier stages, forms in later stages. stages. These habits can be easily traced, traced, in in the the same same mine depositional order, order, not not only only ininthe theThonipsori-Temperly Thompson-Temperly mine they are are well developed, developed, but but throughout throughout the the 3,000 3,000 where they square miles of the the district. district. By contrast, preliminary studies by Philip studies Philip Bethke and Paul Barton on thin thin composcompos­ itional layering itional layering in sphalerite have shown that although this this layering be correlated with confidence throughout the layering can be the Thompson ore body, body, attempts attempts to to trace trace it it even even to to nearby nearby mines mines are, as as yet, yet, inconclusive. are, (3) (3) measurements of thermoluminescence suggest aa Preliminary measurements distinct variation between the distinct the reaction reaction of of barren barren and and alal­ tered rock to to heating. heating. (4) (4) Semiquantitative spectrographic spectrographic analyses analyses of of compositional compositional variations in in minerals of the the altered altered zone, zone, and and quantitative quantitative determinations of the determinations the amounts amounts of calcite and dolomite by aa combination of X-ray diffraction and other geochemical tests. tests. E. Hall and Irving (5) W. E. Irving Friedman's work on on fluid fluid inclusions inclusions (5) from ore ore minerals minerals in the from the district shows ShO\lS that the the mineralizing solutions were highly concentrated sodium-calcium chloride solutions were brines similar to connate waters found today in deep to found today in deep wells wells Temperature in the Illinois basin. basin. Temperature studies studies by by Darrell Darrell Pinckney in Pinckney in the the inclusions inclusions from from the the Thompson-Tentperly Thompson-Temperly mine mine Eugene Roseboom is are in progress. Eugene Roseboom is studying studying the the copper copper H. T. T. Shacklette mineralogy. H. Shacklette has has made made aa district—wide district-wide geo— geo­ botanical study of minor-element variations botanical study of minor-element variations in in the the vegetation. vegetation. 47 47 ��_______ MA PPED NOT -I: MAPPED - —— 77 - LEGEND - Duluth Gabb,o Cornpiee PRELIMINARY SKETCH MAP Li OF THE ELY GREENSTONE in the GABBRO LAKE QUADRANGLE n MINNESOTA Gonts Rang. batbohth (Algoman) kntfe Lax. Group Dact. Porphyry I L liar S ntiflfl) Ely Gr..nstone Iphirulitic mefab010ht conglomerate SCALE ----:c- /2 I 2 miles 49 iron formation 3 4 trend fault of Strata �I', * 0 U V 4 U 'I, E N 0 .5 2 50 - -J A- 1' ��PRESENTATION PRESENTATION OF OF AAREGIONAL REGIONALAEROMAGNETIC AEROMAGNETIC MAP MAP OF OF WISCONSIN WISCONSIN Robert Patenaude Robert Patenaude aeromagnetic map map of Wisconsin Wisconsin is The aeromagnetic is most distinctive in the northwest quadrent of the state by virtue of aa strongly northwest quadrant strongly developed developed northeast—southwest lineation in the contours. northeast-southwest lineation in the contours. The The positive positive magmagnetic zones netic zones appear to coincide in in location location with the the mid-continent gravity high and with Huronian iron iron formation and its its metamorphosed metamorphosed The Gogebic iron range in particular is equivalent. is marked by aa strong positive positive magnetic anomaly. strong anomaly. In the the north north central central part part of of the the state state In anomalies extends to the east and northeast anomalies extends to Wausau. Another group of positive magnetic the vicinity of Eau the Eau Claire. Claiye. A relatively A relatively central Wisconsin Wisconsin central southeast part of of southeast stronger and more a zone of positive from the the vicinity of of anomalies anomalies occurs occurs in in undisturbed undisturbed magnetic magnetic pattern pattern extends extends from from east east to to the the southwest portion of of the the state. state. In In the the Wisconsin the the magnetic pattern pattern again again becomes becomes irregular. irregular. 52 52 �A METHOD FOR COMPUTING THE MAGNETIZATION OF DIKES A METHOD FOR COMPUTING THE NAGNETIZATION OF DIKES WITH WITHEXAMPLES EXAMPLES OF ITS OF ITSAPPLICATION APPLICATIONTO TODIKES DIKESNORTH NORTHOF OFCOVINGTON COVINGTON Gerald Gerald Van Van Voorhis Voorhis and and Lloyal Lloyal Bacon Bacon When interpreting vfuen interpreting the the data data from from aa magnetic magnetic survey, survey, it it is is often often helpful to be able to compute the magnetic anomaly for various helpful to be able to compute the magnetic anomaly for various geogeoBecause of of the magnetic logic structures. logic structures. Because the difficulty difficulty in in computing computing the the magnetic effect of of three-dimensional three—dimensional bodies, bodies, most most computations computations are effect are limited limited to to One of the most frequently encountered the two—dimensional the two-dimensional case. case. One of the most frequently encountered twotwoSince the dimensional structures dimensional structures is is the the dike. dike. Since the depth depth extent extent of of aa dike dike is not not usually usually known, known, and and the magnetic effect effect of of the bottom surface is the magnetic the bottom surface is is small if the depth is large, it is often assumed in making calculations small if the depth is large, it is often assumed in making calculations that the the dike dike extends extends to that to infinity. infinity. inA A formula formula for for computing computing the the magnetic magnetic anomaly anomaly of of aa dike dike of of inf infinFrom Figure 1 it is seen that ite depth extent is given in Figure 1, ite depth extent is given in Figure 1, From Figure I it is seen that the effects of of the magnetization are the effects the dike's dike's dip dip and and magnetization are contained contained in in the the Generally these factors will be unknown. constants 01 C1 and constants and C2. C2 • Generally ~hese factors will be unknown. On On the the otherhand, the variables L L and otherhand, the variables and ~ depend depend only only on on the the depth depth of of burial burial If the the magnetic magnetic anomaly and width width of and of the the dike dike and and are are usually usually known. knotm. If anomaly of the dike has been measured, C1 and C2 can be determined of the dike has been measured, Cl and Cz can be determined by by least least If the dip of of the dike is magnetization in squares. If squares. the dip the dike is known, known, the the magnetization in the the plane plane normal normal to to its its strike strike can can then then be be computed. computed. Frequently, the Frequently, the depth depth of of burial burial of of the the dike dike is is known, knotm, but but its its The available geologic information. width is width is not not known lcnown from from available geologic information. The width width can can Figure 2 be be determined determined from from the the measured measured magnetic magnetic anomaly. anomaly. Figure 2 is is aa plot plot of the the anomaly anomaly and and the the corresponding corresponding L L and and I terms of terms for for aa specific specific term has even symmetry The L L term dike. The dike. term has has odd odd and and the the t term has even symmetry about about the the If the dike anomaly is folded about the center of center of the the dike. dike. If the dike anomaly is folded about the center center as as shown on on Figure Figure 3 3 and and the sum and difference of of the sho~m the sum and difference the resulting resulting curves curves plotted, the the sum sum curve curve will will equal equal ZC2~ 2C2 and plotted, and the the difference difference curve curve will will The maxima and minima of the L term and the points equal 2C1L. equal 2C I L. The maxima and minima of the L term and the points of of at the same distance, distance, r, maximum slope maximum slope of of the the i term term fall fall at the same r, from from the the If aa semicircle semicircle of of radius radius rr is center of of the center the dike. dike. If is drawn drawn as as shown shown on on Figure 3, Figure 3, the the intersection intersection of of the the semicircle semicircle with with the the depth depth of of burial burial plane will will define plane define the the edges edges of of the the dike. dike. analysis of the The above The above techniques techniques have have been been applied applied to to the the analysis of the In one case, oriented samples measured anomalies of known dikes. measured anomalies of knotm dikes. In one case, oriented samples of of check on the least the dike dike had had been been studied studied previously previously and and provided provided a a check the on the least In that that case case the computed results results checked checked with square calculation. calculation. In square the computed with the measured measured values values to the to within within the the error error of of measurement. measurement. 53 53 �mag. mag. north north ) A ! si - ----- 8B / / i, .,e /' I I / c ~,,/ I ~o/ -i <:</ / / I / \ L I 8 8 0 C1L+ C2 anomaly = anomaly c L = 22Iog(R1/R2) log (R 1 / R ) 2 mag. north '\,..---- ~ = 22(Ø1CØ2) (0 1(+) ~~\ ) A Hsini 2 A= Hn sln i +Z Z Slnl sin i cos I COSI + .J.- Z z Z sin sini -H sin I cosi cos I B = Z -Hsini B n 1- r----··------,-------- -- .-_. I I component component in-no. ---------vertical vertical I I total field - - -- I i C1 Cl I - ---------- ------------------, C2 --r--------- ---- -------------------l----- --------..-- ------------------r I A I h or z ant a I horizontal un - B I B II I A A sin B cos I sin s _f~~~_L_:_~~~~ __~B c~_~_~_~_~~~ J_~~~_s_~ sS'lnn sS - ~~~~_I __ J Ltota_1 Figure 1. Figure 1. I i + Geometry, notation, notation, and and formula forrnua for for infinite Geometry, infinite dike. dike. 54 S4 I �fI anomaly I = C L ÷ C2 > 4J .. , (I) C .-' C uU "—— . , .... fIIII" ......... ..... __ - - - ,,-..... • I •• • • I \ ' · .... ~C2~ , ,, +-' OJ . ',I . 'I cC (J) cn a o \' " E E I ".- " ,_ ....\.. ... -- --- ---- ~ -1-- C, LL C1 i I Figure Fig ure 2. 2. Illustration Illustrat ion symmetry of 0 f sym met r y used used for for dike di ke width width determination determination. sum = ..~sum i 2C2 I >, I +-' 4. If) c OJ +-' c U u +-' C) OJ C C ,- , - -' \ f- difference = difference .. ... .... 2 C 1 LL = 2C1 \ 01 0a — folded ""--f"-fold ed anomaly an oma Iy E E I I I -S , Figure 3. 3. Anomaly folding to to obtain Figure Anomaly folding obtain terms. terms. 55 55 sum sum and and difference difference 't ' is , �THE APPLICATION OF OF RADIO RADIOFIELD FIELDINTENSITY INTENSITY MEASUREMENTS TO TO THE MEASUREMENTS MAPPING PRECAMBRIAN GEOLOGICAL NAPPING PRECAMBRIAN GEOLOGICAL FEATURES FEATURES Charles E. Kerman Kerman and and William William J. J. Hinze Hinze Charles E. intensity of of radio radio waves waves received received from from A.N. A.M. broadeasting broadeasting The intensity The stations is a function of many factors including the and stations is including the electrical electrical and magnetic properties of the the underlying earth earth formations. formations. In In areas areas where the effects effects of of the the earth earth formations formations are are great great enough enough to to override override where the the other factors or the other factors can be eliminated~ the the factors factors eliminated, the radio field intensity method can be utilized for detecting changes in in these these field intensity method can be utilized for detecting changes physical properties. These These physical physical properties properties may may be be related related to to spe. spe cific geological formations formations and and structures, structures, therefore therefore this this method method is is cific geological potentially applicable applicable to to geological geological mapping. mapping. A radio field field intensity intensity survey survey was lIas conducted conducted in in the the Marquette, Marquette, A radio Iron areaS of of the the Northern PeninPeninIron Mountain, Mountain, Ironwood~ Ironwood, and Keweenaw areaB sula the applicability of this this method to to sula of of Michigan Michigan to to determine determine the mapping Precambrian Precambrian geological geological features features in in the the Lake Lake Superior Superior region. region. mapping Measurements were made from from aa vehic'e vehicle utilizing utilizing continuous continuous recording recording techniques. Correlation of of radio radio field field intensity intensity variations variations with with known geology 3eology indicates indicates that that this this method method offers offers promise promise as as an an econonieconomical and and rapid rapid method of of geological geological mapping mapping particularly particularly for for tracing tracing and extending known known faults, faults, contacts, contacts, and and formations formations where where cultural cultural and topographical topographical effects effects are are not not severe severe and and the the glacial glacial drift drift is is thin. thin. 56 �INVESTIGATION OF THE THICKNESS OF THE THE JACOBSVILLE SANDSTONE SAZ!DSTONE BY SEISMIC REFLECTION --A BY REFLECTION METHODS METHODS -A PROGRESS PROGRESS REPORT REPORT Lloyal 0. L10ya1 O. Bacon Bacon The area just just east and south of the the Keweenaw KeHeenal'1 fault fault has aa very section of Jacobsville sandstone of Cambrian (Ozarkian?) age. thick section (Ozarkian?) age. Previous gravity work by the author indicated indicated a throw throl-l of the the Keweenaw Keloleenaw fault of of the the order order of 10,000 feet, feet, with an indication that fault that a parallel fault existed existed to to the the east east and and the the possibility of at at least one major fault A seismic lecnearly normal to to the the strike strike of of the the Keweenaw Keweenaw fault. fault. A seismic ref reflection program was instituted to to check check the the gravity gravity interpretation. interpretation. Seismic reflections reflections can be obtained from within or at the the base of the the sedimentary section if appropriate care is is used in shot lolowith the use of multiple geophones mixing. cation and nith geophones and signal mixing. The seismic seismic evidence substantiates substantiates previous estimates estimates of of about about 10,000 feet feet throw throw for for the the Keweenaw Keweenaw fault; fault; honever, however, the the limited data 10,000 limited data does not substantiate the presence of a cross fault near obtained does Limestone Mountain as as interpreted interpreted from from gravity gravity data. data. 57 57 �OF INDUCED THE APPLICATION OF INDUCED POLARIZATION POLARIZATIONPROBING PROBINGTECHNIQUES TECHNIQUESUNDERGROUND; UNDERGROUND; MICHIGAN NATIVE MICHIGAN NATIVE COPPER COPPER DISTRICT A. W. Schillinger Schillinger Exploration drilling with a success factor factor (discovery (discovery ratio) ratio) of of only 347 did not not initially prove prove entirely satisfactory in the search 34% did for native native copper copper mineralization mineralization in the footwall of the Amyg— for the footwall the Osceola Amygdaloid workings. Mining experience proved the oreshoots to to be more continuous than drilling results results indicated, indicated, but additional fill-in fill-in drilling was ~7as impractical. An auxiliary exploration tool was needed. needed. At the the request of Calumet && Hecla, Inc., Inc., the the Geophysics Department Department of of Michigan Technology University evaluated evaluated the the measurable electrical electrical properties of native copper copper mineralization and recommended recommended that that their their efforts be be directed to efforts to developing an induced polarization method adaptable to able to drill hole probing techniques. techniques. As developed by the the University, the the apparatus apparatus consists of of aa semisemirigid coiled probe and a power supply/instrument case easily easily transported transported A standard and operated by one and one man. man. A standard AM (3 (3 electrode) electrode) logging logging configconfigresulting in in a uration is used with aa spacing spacing of of 2' 2' -- 4' 4 tt -- ,::"_ resulting a sampsampling radius of 5'±. ling 5'+. Readings Readings are are generally generally taken taken at at two-foot two-foot interintervals in in the the hole. hole.- The three probe electrodes are are sponge-covered, sponge-covered, nonnonpolarizing lead/lead oxide types and the remote current electrode electrode is is wire gauze. gauze. AA constant constant current current of of 5, 5, 10, 10, or or 20 20 ma. mao of of alternately alternately rerePotential readings versed polarity is is pulsed pulsed at at 3.5 3.5 sec. sec. intervals. intervals. Potential readings are are During the taken during during the the "on" ont cycle taken cycle for for resistivity resistivity determinations. determinations. During the "off" cycle, cycle, after after aa 10 10 ms. ms. delay, delay, the the I.P. I,P. potential is "off" is sampled for for a data is is computed computed in 10 ms. ms. interval and 10 and recorded. recorded. Field Field data in the the office office and both resistivity values (ohm-feet) (ohm-feet) and "S" liS" values (mv/v) (mv/v) are are plotted together on semi-log semi-log paper. paper. The The interpretation interpretation of of the the probe probe results results consists consists of of (1) plotting plotting aa lithologic lithologic log log based based on the the calculated resistivity, (1) resistivity, and (2) delimiting, delimiting, on on aa semi-quantitative semi-quantitative basis, basis, anomalous anomalous zones (2) zones based on inspection of the the "S" "s" values and their corresponding resistivity resistivity Amygdaloid, averaging values. The Osceola Amygdaloid, averaging 30 30 feet feet in in true true thickness, thickness, consists of hanging-wall, hanging—wall, intermediate, consists intermediate, and footwall foot~7all amygdaloidal amygdaloidal zones zones of low resistivity separated by one or more "bars" or sills of high of low resistivity separated by one or more "bars" or sills of high resistivity footwall-type footwall-type basaltic basaltic trap. trap. Comparing Comparing aa large large number number of of lithologic resistivity resistivity logs logs with with the lithologic the corresponding core logs logs showed showed that that remarkably good correlation was obtainable and amygdaloid-trap contacts contacts Based could frequently be picked picked to could frequently be to +.5' +.5' from from resistivity resistivity logs logs alone. a10n~. Based on resistivity data, it was now possible to make up geologic logs of on resistivity data, it was now possible to make up geologic logs of long steel steel holes holes to augment or even replace replace the long to augment the time-consuming, time-consuming, only Based on partially satisfactory partially satisfactory sludge sludge logging logging procedures. procedures. Based on laboratory laboratory data and empirical observations in mining areas, a threshold data and empirical observations in mining areas, a threshold "S" "s" value value 58 58 �diagnostic induced of 30 30 mv/v mv/v tlaS was established established as as the of diagnostic of the lower lower limit limit of induced Above 30 mv/v polarization effects in mineralized anygdaloidal vein. polarization effects in mineralized anygdaloidal vein. Above 30 mv/v 50 mv/v); "fair" anomalous zones were designated anomalous zones were designated "slight" "slight" (30 (30 — 50 mvlv); "fair" mv/v) and "very good" (plus 200 200 mvlv) mv/v); "good" 100 mvlv); (50 (50 - 100 "good" (100 (100 -- 200 and "very good" (plus 200 grade values to No attempt has been made to mv/v). No attempt has been made to assign mvlv). assign absolute absolute grade values to better are concorresponding "S" values, although two points "fair" or better corresponding IISI1 values, although t",o points "fair" or are considered ore sidered ore from from aa development development standpoint. standpoint. M steel holes aggregating Since 1956, Since 1956, 876 876 diamond diamond drill drill and and lcng long steel holes aggregating workings. Of the 47,000 feet have been drilled in the Osceola mine uorkings. 47,000 feet have been drilled in the Osceola mine Of the probed witch the I.P. 914 footwall footwall zones zones penetrated, penetrated, 316 316 have have been been probed 914 with the I.P. The success factor anomalies. The equipment yielding yielding 203 or better better anomalies. equipment 203 "fair" "fair ll or success factor drilling oniy to 727. for (discovery ratio) has increased from 34% for (discovery ratio) has increased from 34% for drilling only to 72% for Forty—six probe results were checked drilling and drilling and probing probing combined. combined. Forty-six probe results \Jere checked the interpretations were by by subsequent subsequent drifting drifting or or crosscutting crosscutting and and the interpretations \~ere Incorrect results consisted of found to of the found to be be correct correct 787. 78% of the time. time. Incorrect results consisted of all or of the interthe probe probe not not detecting the detecting copper copper mineralization mineralization at at all or However, of the interin no of an anomaly. preter underestimating preter underestimating the the significance significance of an anomaly. However, in no case was Case was aa false false anomaly anomaly found. found. the discovery ratio two- The use The use of of the the I.P. I.P. probe probe has has increased increased the discovery ratio tworadius of exploration holes fold by by greatly greatly increasing increasing the the sampling sampling radius fold of exploration holes footwall ore than drill results and has has proven proven a and a greater greater continuity continuity of of footwall ore than drill results be employed In addition, long steel drilling can now now be alone indicate. alone indicate. In addition, long steel drilling can employed be plotted more accurwith more more confidence confidence inasmuch with inasmuch as as contacts contacts can can be plotted more accur the necessity of saving sludge ately and and ore ore zones ately zones delineated delineated without without the necessity of structures, saving sludge favorable maxHowever, in samples. However, samples. in the the search search for for ore ore and and favorable structures, maxbe realized if geofrom the use of the probe can only imum results imum results from the use of the probe can only be realized if geointerpretation of the data and its logical reasoning reasoning is logical is applied applied in in the the interpretation of the data and its subsequent use subsequent use on on geologic geologic plans plans and and sections. sections. M 59 59 ��Table 11 Table Analytical Data Analytical Data for for Duluth Duluth Gabbro Gabbro M.I.T. H.l.T. Sample Sample Rock Type Rock Type 4364 4364 4361 4361 4363 4363 4365 4365 4362 4362 Granophyre Granophyre Granophyre Granophyre Granophyre Granophyre Granophyre Granophyre Anorthositic Anorthositic Gabbro Gabbro Gabbro, Layered Gabbro, Layered Series Series Gabbro Gabbro 4366 4366 1231 1231 j"sr::l r86 sr871 'Sr ~ Rb87 87 Rb SrS6 . S"rB"6' 2.62(2 2.62(2~ 0.7408 0.740B 0.7218 0.721B 0.7146 0.7146 0.7114 0.7114 0.7087 0.7087 1.07(2) 1.07(2) 0.63 0.63 0.42 0.42 0.23 0.23 0.7049(3) 0.7049(3) 0.07 0.07 0.7065(2) 0.7065(2) 0.06 0.06 Table Table 22 Analytical Data Analytical Data for for Endion Endion Sill Sill Granophyre Granophyre Granophyre Granophyre Intermed. Rock Rock Intermed. Diabase Diabase 4373 4373 4372 4372 4371 4371 4369 4369 0.7839 0.7B39 0.7402 0.7402 0.7163 0.7163 0.7136 (2) 0.7136(2) 5.22 5.22 2.29(2) 2.29(2) 0.78 0.78 0.55 0.55 All All Sr87/Sr86 SrB7 /Sr B6 ratios ratios have have been been corrected corrected for for fractionation fractionation by by normalizing normalizing to to Sr86/Sr88 Sr B6 /Sr B8 = 1194. = 0. 0.1194. Numbers in brackets indicate Numbers in brackets indicate the the number number of of measurements measurements made. made. 61 61 �0.780 FIGURE I I 0.760 87 S/7 Sr -86 86 Sr 0.74 0 0.740 0 o DULUTH 0.720 0.7 20 V 00 T97:,I.O0t 0.07 B.Y. [ST~7]=,,1.00±0.07 B.Y. 0/ ,0 8. GABBRO ". 86 Sr 0 0.7 0 Ol.......-_ _----L. 0.700 1.0 ± 0.0009 0.0009 = 0.7052 0.7052 ± 0 ....l.....-_ _- - - l ----l...... 2.0 87 Rbi Sf6 Rb/Sr 86 I I I 3.0 4.0 ----I..._-J 5.0 I 0 o 0.780 0.780 FIGURE FIGURE / 22 0.760 0.760 87 Sr87 Sr 86 Sr96 Sr 0.740 0.740 o0 ENDION SILL ENDION SILL 0.7 20 0.720 /0 o o0.700 .700 T T ,0 • I..08 08 z ±0.05 ± 0.05 B.Y. B. Y. 0.7050±0.0009 [~:~: 0.7050 ± O. 0009 .L....-_ _----I.. 1.0 ---L... 2.0 R8;s~6 Rb8Sr 82 ....J.....- 3.0 .L.....-_ _----J..._---" 4.0 5.0 �� https://digitalcollections.lakeheadu.ca/files/original/df3cc93218f5673f9364658638861275.pdf 0819b5112b00282b9e5c563c678b7086 PDF Text Text THE CLEVELAND-CLIFFS IRON COMPANY PAPER ON The Marquette Mineral District Michigan 1964 Presented to the Conference on Lake Superior Geology National Science Foundation Summer Conference Sponsored by Michigan Technological University BY BURTON H. BOVUM CHIEF GEOLOGIST ISHPEMING. MICHIGAN �17 17 THE MARQUETTE THE MARQUETTE MINERAL MINERAL DISTRICT, DISTRICT, MICHIGAN MICHIGAN by by Burton Burton H. H. Boyum, Boyum, Chief Chief Geologist Geologist Mining Department Mining Department The Cleveland-Cliffs The Cleveland-Cliffs Iron Iron Company Company Ishpeming, Michigan Ishpeming, Michigan General Sett General Setting The Marquette Marquette Mineral Mineral District District of is situated The of Michigan Michigan is situated in in Marquette Marquette It was the first Countyand andthe theeast east central central part County part of of Barage Barage County. County. It was the first of of the the Lake Superior iron iron districts Lake Superior districts to tobe be discovered discoveredand and mined; mined; and and iron iron mining mining There has continues to to be be the the major major mining activity to to this this date, continues mining activity date. There has also also been been Figure 11 shows some production some production of of gold. gold. Figure shows the the outlined outlined location location of of the the Negaunee Negaunee Geographically, the iron-formation, the iron-formation, the principal principal host host rock rock for for the the iron iron ore, ore. Geographically, the Marquette Marquette District District is is located locatedon onaa topographic topographichighland highland rising risingsome some600 600to to1200 1200 above Lake Lake Superior Superior (mean feet above feet (mean sea sea level level elevation elevation+602 +602 feet). feet). The The average average 1400 feet. feet. ground elevation near near the ground elevation the mines mines at atIshpeming Ishpeming and and Negaunee Negaunee is is ++ 1400 feet. Locally, 1875 feet. Firetower Hill area rises Firetower Hill in in the the Tilden Tilden Mine Mine area rises to to ++1875 Locally, the the is rugged, with numerous lakes and swamps. The watershed topography topography is rugged, with numerous lakes and swamps. drains both both to toLake LakeSuperior Superiorand andLake Lake Michigan Michigan from from the the Marquette Marquette high­ high drains By tradition, tradition, in the Lake Superior Region, the topographic highs land. By in the Lake Superior Region, the topographic highs in in which most ofofthe theiron irondistricts districts are are found foundare are called called "ranges"; Iranges; hence which most hence the the designation, the the Marquette MarquetteIron IronRange. Range. The The three three principal principal cities cities are are designation, Marquette (County seat and port), Ishpeming and Negaunee. Forest Marquette (County seat and port), Ishpeming and Negaunee. Forest products, products, education (Northern (Northern Michigan Michigan University) University) and and tourism tourism augment in the education augment mining mining in the area's economic activity. area's economic activity. Historical Setting Historical Setting The first miners in in the the region region may may have have been the the pre~historic prehistoric Indian The first miners Indian 1961). We We know know copper miners miners some some 3800 (Drier and and DuTemple, DuTemple, 1961). copper 3800 years years ago (Drier that the French explorers, Brule and Grenoble, visited the Upper Peninsula that the French explorers, Brule and Grenoble, visited the Upper Peninsula in 1E>22. 122. They voyageurs. in Theywere werefollowed followedby byfur fur traders, traders, missionaries and voyageurs. In 1668 Father Jacques Marquette and Father Claude Dablon established In 1668 Father Jacques Marquette and Father Claude Dablon established the the believed that that Father Father Marquette Marquette visited It is n-ission at at Sault mission Sault Ste. Ste. Marie Marie (Soo). (Soo). It is believed visited site of and used used aa campsite campsite at the site of the the City City of of Marquette Marquette in in 1670 1670 and and 1671 1671 and at His name was given to the city, county and iron range Lighthouse Point, Lighthouse Point, His name was given to the city, county and iron range in in �18 honor of of his his early early work work here, here, as honor as well well as as his his extensive extensive efforts efforts in in other other parts parts of of He assisted assisted Fathers the north north central central states. states. He the FathersAllouez Allouezand andDablon Dablon in in making making the the first map in 1672 in Paris. Paris. Sporadic first map of of the the Lake Lake Superior Superior Region, Region, published published in 1672 in Sporadic fur fur trading marked marked the the next next 170 170 years years in in this this vicinity. trading vicinity. Michigan became became aa State Dr. Douglass the first first State Michigan State in in 1837. 1837. Dr. Douglas s Houghton, Houghton, the State Geologist, convinced the State State Legislature Legislature that Geologist, convinced the that the the Federal FederalLand LandSubdivision Subdivision The Indian Indian Treaty Treaty of Survey should should have have geological geological mapping as an Survey mapping as an adjunct. adjunct. The of LaPointe, 1842, LaPointe, 1842, opened opened the the Upper Upper Peninsula Peninsula to to the the white white men. men. On OnSeptember September 19, 1844, Survey Party Party under 19, 1844, a a Government Government Survey under Mr. Mr. William William A. A. Burt Burtwas was running running Shaft the east line of Section 1, T. 47 N. and R. 27 W. (Mather Mine the east line of Section 1, T. 47 N. and R. 27 W. (Mather Mine nBt! property). AA younger Jacob, noted erratic property). younger brother brother of of Douglass Douglass Houghton, Houghton, Jacob, noted erratic They sought sought the the cause cause and and found, found, as compass behavior. compass behavior. They as recorded recorded by by Douglass Douglass Houghton, rrSpathose "Spathoseand andmagnetite magnetiteores oresabounding. abounding." Later, in Houghton, rr Later, in 1846, 1846, Burt Burt wrote: ItrrItmay wrote: maybe bereasonably reasonablyinferred inferredthat thatnot notmore morethan thanone-seventh one-seventh of of the the of Iron Iron ore ore beds beds were were seen Township lines; number number of seen during during the the survey survey of of the Township lines; mines be subdivided with care care in in reference district of ofTownships Townships be this district and if and if this subdivided with reference to to mines If this view minerals, six times as many more will probably be found. and minerals, six times as many more will probably be found. If this view of of the Iron the Northern Northern Peninsula Peninsula of of Michigan Michiganbebecorrect, correct, itit far the Iron region region of of the far excels excels any other other portion States in qualities of its any portion of of the the United United States in the the abundance abundance and and good good qualities of its Iron ores. ores."rr Iron Word of ore discovery discovery spread state and and elsewhere elsewhere Word of the the iron ore spread through through the the state group of ofmen men from from Jackson, Jackson, Michigan, Michigan, formed formed In 1845 that winter. during that winter. In 1845 aa group The treasurer, Philo Everett, and his associthe Jackson Jackson Mining Mining Company. Company. The treasurer, Philo Everett, and his as sod­ the story is ates, reached reached Teal ates, Teal Lake Lake in in June. June. The story is told told that that the the Indian Indian chief, chief, stump sick, showed them the high grade hard ore under the Marji-Ge Marji-Gesick, showed them the hard under the stump of of a a ore pine tree. tree. By By 1846, 1846, there there were were 106 106 mining mining companies. companies. The fallen pine fallen The first first ore the Soo Soo Locks Locks opened opened 7, 1852. barrels on July 7. shipped consisted shipped consisted of of six six barrels 1852. After the June, 1855, in June, 1855, Lake Lake Superior Superior iron iron mining mining boomed boomed -- a tribute tribute to to the the farsighted farsighted vision of vision of Douglass Douglass Houghton. Houghton. Since much much ofofthe theore ore was wasfound foundatatorornear near surface, surface, the Since the early early mines mines were were As the mines went deeper, worked by open pit methods, as shown in Figure 2. worked by open pit methods, as sho\VTI in Figure 2. As the mines went deeper, skip roads roads were were used bring the the ore oretotosurface. surface. By By 1880, 1880, most most of inclined skip inclined used to to bring of the ore was was produced produced from from underground underground workings. the ore workings. Early methods were were open open by top-slicing stoping, room-and-pillar stoping, and square-sets, followed stoping, room-and-pillar stoping, and square-sets, by top-slicing Large scale Sub-level caving caving was was used used where where conditions permitted. Large in 1890. Sub-level in conditions permitted. scale illustrates a sub-level stoping Figure 3 block caving was was introduced in 1950. introduced in 1950. Figure 3 illustrates a sub-level stoping scene. scene. Emphasis in Emphasis in mining mmmgwas wasplaced placedononthe the high high grade grade direct direct shipping shipping ores. ores. the 1880t5 several attempts attempts were However, in However, in the 1880's several were made made to to use use concentrating concentrating plants. plants. It produced Edison built a magnetic separator at Humboldt in 1888. Thomas Edison built a magnetic separator at Humboldt in 1888. It produced Thomas World War War grade concentrate burned in 893 tons of of high grade concentrate before before it it burned in 1889. 1889. After After World II, the mining companies worked on developing economic processes of con II, the mining companies worked on developing economic processes of con­ �• • 19 19 centrating grade Negaunee Negauneeiron-formation, iron-formation, also also called centrating the the low low grade called jaspertr ffjasper rr or or The first commercial plant, opened in 1954, was the Humboldt ttaconite. rttaconite. The first commercial plant, opened in 1954, was the Humboldt Mine of of The The Cleveland-Cliffs Cleveland-Cliffs Iron Iron Company Companyand andFord Ford Motor Motor Company. Company. The Mine The Repuolic Mine was opened in 1956, and the Empire Mine in 1963; both partnerRepuolic Mine was opened in 1956, and the Empire Mine in 1963; both partner­ ships of ships of various various steel steel companies companies and and Cleveland-Cliffs. Cleveland-Cliffs. All All three three open open pit pit properties produce grade pellets. properties produce high high grade pellets. II The Marquette Marquette Iron Iron Range Rangeisis made made up upofofthree three districts districts (see The (see Figure Figure 4). 4). From 1852 through 1963, the iron ore production from these districts was: From 1852 through 1963, the iron are production from thes e districts was: Principal Principal district district Cascade district Cas cade district Gwinndistrict district Gwinn 291,323,507 291,323,507 17,895,700 17,895,700 785, 260 12, 12,785,260 Total Total 322, 004,467 long 322,004,467 long tons tons Of the the total total of of291 291million milliontons tonsproduced produced from from the part of of the the Range, Range, Of the principal principal part 4,266,858 long tons were from the Bijiki iron-formation, and the balance was 4,266,858 long tons were from the Bijiki iron-formation, and the balance was from the Negaunee iron-formation. from the Negaunee iron-formation. Concentration was was accomplished Concentration accomplishedononthe the Bijiki Bijiki iron-formation iron-formation by by using using total heavy media media process the Ohio OhioMine. Mine. From From 1952 the heavy the process at at the 1952 to to 1960, 1960, a a total of of pit operations. 745, 620 long tons of concentrate was produced from several open 745,620 long tons of concentrate was produced from several open pit operations. Local Not all all Marquette Marquette Range Range ores Not ores were wereshipped shippedtotothe the blast blast furnaces. furnaces. Local charcoal furnaces, furnaces, used used from from 1857 charcoal 1857 through through 1893, 1893, produced produced an an estimated estimated one one and aa half million million and tons tons of of pig pig iron. iron. Sett Geologic Geologic Setting The principal principal rock rock units units are are Precambrian The Precambrian in in age. age. Structurally, Structurally, they they are are al, to the Southern Province of the great Canadian Shield (Leech et assigned to the Southern Province of the great Canadian Shield (Leech et aI, assigned Probably they were subjected the major major orogenies orogenies of of the theKenoran Kenoran and and 1963), Probably 1963). they were subjected to to the Penokean (Hudsonian, Stockwell, 1962), as well as more local deformation, Penokean (Hudsonian, Stockwell, 1962), as well as more local deformation. which the found was was called The thick sedimentary sedimentary series series in The thick in which the iron iron ore ore is is found called next century. by Whitney in 1857, and the term was used for the Huronian by Whitney in 1857, and the term was used for the next century. (1958)pointed pointedout outthat thatthe theseries series differs differs considerably James (l958) considerably from from the the type type section of the Huronian of Ontario and is more firmly correlated with section of the Huronian of Ontario and is more firmly correlated with the the Animikie series series of Animikie of northeastern northeastern Minnesota; Minnesota; therefore, therefore, the theUnited United States States GeolGeol­ Goldich, et al (1961) dated the Animikie ogical Survey uses the term Animikie. ogical Survey uses the term Animikie. Goldich, et al (I96l) dated the Animikie practice, Stockwell as middle Precambrian in as middle Precambrian in age. age. By ByCanadian Canadian practice, Stockwell(1962) (1962) would would term Animikie as Lower Proterozoic. term Animikie as Lower Proterozoic • �20 The found in in aa long long westward westward plunging plunging synclinorium The Animikie Animikie series series isis found which County line, the south south line, the which opens openstoto the the west west (see (see Figure Figure 4). Near the Barage County limb syncline has has been been folded folded into a lesser lesserdownfold downfold called called the the limb of the the major syncline The sedimentary sedimentary series series continues Republic Trough. The continues into into Baraga, Baraga, Dickinson Dickinson Republic Trough. and Iron Counties. Older and (Archean) rocks rocks are are found found to to the the north north of Older (Archean) of the the syn~ syn clinorium, To To the south is clinorium. granite complex, complex, thought thought to to be be related related to to the the is aa granite folding of against the the older rock to the the north. north. of the the synclinorium synclinorium against rock buttres buttresss to to the Cascade Range, immediately The Cascade immediately to the southeast southeast of of the the Marquette Marquette synsyn­ clinorium, is considered considered to to be be aa faulted faulted segment segment of of the the main main structure. structure. The clinorium, is or Swanzy Swanzy area, Negaunee, and Dead Gwinn area, some some 20 20 miles miles southeast southeast of of Negaunee, and the the Dead Gwinn or of the the Marquette Marquette Range, Range,are are separate separate basins, River area, basins, area, a few miles north of entire district to contain contain rocks rocks of of the the Animikie Animikie series. thought to thought series. The The entire district has has been been intruded by rocks of Keweenawan age. Cambrian and Ordovician sandstones intruded rocks of Keweenawan age. Cambria.n and Ordovician sandstones district was and limestones limestones are and are found found to to the the south south and and southeast, southeast. The The district was glaciated glaciated extensively. extensively. Stratigraphic Column Stratigraphic Column A schematic schematic summary summary of the stratigraphic A of the stratigraphic column column is is shown shown as as the the legend legend This column is aa modification the most on Figure Figure 4. on 4. This column is modification of of the most recent recent work work by by the the United States States Geological Geological Survey, Survey, together together with United with data data from from the the mining mining companiest companies I drill hole undergroundand andsurface surfaceexposure exposureinformation. information. Figure Figure 44 is drill hole and and underground is aa plan map map indicating indicating the the principal principal Animikie and older older rock plan Animikie and rock units units which which make make up up the Marquette synclinorium and environs, Figures 5 and 6 illustrate spatial the Marquette synclinorium and environs. Figures 5 and 6 illustrate spatial relations of relations of the the principal principal rock rockunits units in inthe thevicinity vicinityofofNegaunee Negaunee and and Ishpeming. Ishpeming. Figure 77 indicates the relative Figure indicates the relative thicknesses thicknesses of of the the stratigraphic stratigraphic units units from from east east reflect several to west west in to in the the synclinorium. synclinorium. Variations Variations reflect several features features such such as as the the extent of of primary primary sedimentation and later later erosion. extent sedimentation and erosion. Apparently Apparently the the locus locus of of the sedimentation westerly as the sedimentation moved moved westerly as the the younger younger ro.cks rocks were were being being deposited. deposited. Pre-Animikie Pre-Animikie Basement Basement Complex Complex Both Monographs Monographs 28 28 and and 52 52describe describe the and Kitchi Kitchi schists Both the Mona Mona and schists which which They were were intruded were called metasediments and were called Keewatin Keewatin metasediments and metavolcanics, metavolcanics. They intruded by flLaurentian by Laurentian"granites, granites.now nowrepresented representedby by granites granites and and gneisses. gneisses. Recent detailed detailed mapping mapping by bythe the U. U.S. Survey (Gair (Gair et et aI, al, 1963, Recent S. Geological Geological Survey 1963, et seq.) that the the Mona Monaschist schist consists consists of of schistose schistose and and massive massive meta­ meta et seq.) has has found found that basalt, actinolitic and chioritic schists, ellipsoidal greenstone, chioritic slate basalt, actinolitic and chloritic schists, ellipsoidal greenstone, chloritic slate and felsite. felsite, This This thick thick series series isis intruded and intruded by by tonalite tonalite and and granodiorite, granodiorite, with with �21 some monzonite, monzonite, quartz The dikes dikes and and sills sills cutting some quartz monzonite monzonite and and granite. granite. The cutting the the Mona schist felsic porphyry, porphyry, frequently frequently weathering weathering to to aa pale pale pink pink color. color. Mona schist are are felsic A the Animikie A widespread widespread unconformity unconformityseparates separatesall all these these rocks rocks from from the Animikie series. series. Animikie Series Animikie Series Chocolay Group Group Chocolay Three formations Three formations make make up up the the Chocolay Chocolay Group Group of of lower lower Animikie Animikie sediments. sediments. The basal basal unit unit is is the the Mesnard quartzite, which is aa vitreous, The Mesnard quartzite, which is vitreous, medium-grained, medium-grained, thin to to thick thick bedded beddedquartzite, quartzite, locally locally brecciated, brecciated, with thin with cross-bedding cross-bedding and and ripple marks. ripple marks. Near NearEnchantment Enchantment Lake, Lake, about about 44 miles miles southwest southwest of of Marquette, Marquette, the basal basal portion is made of conglomerate, conglomerate, graywacke, graywacke, arkose, arkose, and the portion is made up up of and sericitic slates sericitic slates and and quartzites quartzitesalthough although not not all all of of these these types types are arefound found in in the the same location. same locaUon. The Kona Konadolomite dolomiteoverlies overlies the the Mesnard Mesnard formation formation and and is is the The the thickest thickest and and most extensive most extensive member member of of the the Chocolay Chocolay Group Group in in the the area area between between Marquette Marquette and and It is is principally Negaunee, It Negaunee. principally a a light-colored light-colored fine fine to to medium-grained medium-grained massive massive Locally itit has has thin thinlaminated laminatedchert chertlayers, layers, sericitic sericitic slate, dolomite. Locally dolomite. slate, quartzites quartzites In places places the is extensively and laminated laminated siltite. siltite. In and the dolomite dolomite is extensively silicified. silicified. Recent Recent mapping (Fritts, 1964) identifies some quartzitic areas as Kona, rather mapping (Fritts, 1964) identifies some quartzitic areas as Kona, rather than than describes the Mesnard as as mapped earlier. Gair Mesnard mapped earlier. Gair et et al al (1961) (1961) describes the silicification silicification of of rSilicified Kona Konadolomite dolomite most most typically typically consists consists the Kona dolomite as as follows: the Kona dolomite follows: rrSilicified laminations are are of thick thick laminated laminated masses masses of fine-grained quartz quartz (chert). of of fine-grained (chert). The The laminations reddish or variations in reddish or bluish bluish black black to to white, white, depending depending on on variations in minor minor amounts amounts of of Massive siliceous rock consisting different iron iron oxides from layer layer to different oxides from to layer. layer. Massive siliceous rock consisting of of fragments of white chert chert in in aa reddish-brown hematitic cherty fragments of white reddish-brown hematitic cherty matrix matrix apparently apparently resulted from resulted from post-brecciation post-brecciation silicification silicificationof of the the dolomitic dolomitic portion portion of of laminated laminated Thin sections sections of cherty dolomite. cherty dolomite. Thin of silicified silicified dolomite dolomite generally generally show show aa fine-gràined fine-grained mosaic of cherty quartz quartz with small loose loose clusters mosaic of cherty with small clusters of of very very fine-grained fine- grained carbonate carbonate Not only only the the dolomitic dolomitic portions portions of have been been silicified silicified but particles. rr Not particles. of the the Kona Kona have but the slates slatesand andquartzites quartziteshave havebeen beenimpregnated impregnated and and cut cutby bynumerous numerous also the also quartz veins. Another distinctive the Kona Kona is the presence presence of Another distinctive feature of of the is the of the the algal structures, occur widely although they they are are not which occur widely throughout throughout the the Kona Kona although not confined confined to to any any given given Algal structures are locally associated with olites, which confirms horizon. horizon. Algal structures are locally associated with O'~lites, which confirms their shallow-water their shallow-water origin origin (Gair, (Gair, 1962, 1962, oral oralcommunication). communication). The uppermost uppermost member Group is is the slate, which The member of of the the Chocolay Chocolay Group the Wewe Wewe slate, which has an has an estimated estimated maximum maximum thickness thickness of of nearly nearly 900 900 feet, feet. It It is is aa gray gray to to greenishgreenish­ gray, laminated to massive slate, with interbeds of impure dark quartzite. gray, laminated to massive slate, with interbeds of impure dark quartzite. A A �22 Elsewhere, the is brecciated conglomerate is conglomerate is found found locally. locally. Elsewhere, the Wewe Wewe is brecciated and and imim­ In places places the the rock has textures pregnated with with quartz quartz and and specular specular hematite. pregnated hematite. In rock has textures which suggest suggest the the presence presence of of volcanic volcanic and andpyroclastic pyroclastic materials materials (Gair, which (Gair. 1962, 1962, oral communication). oral communication). Seaman (1944) (1944) assigned assigned the to the Seaman the Wewe Wewe to the upper upper Kona; Kona; Boyum Boyum (1954, (1954, 1963) 1963) followed the the same same practice. practice. This followed This report report reflects reflects the the recent recentTi. U. S. Geological Geological Survey mappingand andre-instates re-instates the as aa distinct Survey mapping the Wewe Wewe as distinct formation. formation. Menominee Group Menominee Group The MenomineeGroup Groupisis named namedfor for the the Menominee Menomineedistrict district of The Menominee of southern southern James (1958) assigned this name to the middle Animikie Dickinson County. Dickinson County. James (1958) assigned this name to the middle Animikie rocks rocks of of the the Marquette Marquette Range Range comprising comprising the the Ajibik, Ajibik, Siamo Siamoand andNegaunee Negaunee There appears to be an erosional disconformity between formations. formations. There appears to be an erosional dis conformity between the the Chocolay and and Menominee Menominee Groups. Groups. Chocolay The Ajibik Ajibikquartzite quartzite isis vitreous, vitreous, medium-grained, The medium- grained, thin thinto tothick thickbedded, bedded, with some some sericitic sericitic to to chloritic chloritic slate. with slate. AAbasal basalconglomerate conglomerate is is found found in in Section 6, T. T. 47 Section 6, 47 N., N., R. R. 25 25 W., W., and and elsewhere. elsewhere. The Siamo Siamo slate slate formation formation contains laminated to to massive massive dark The contains laminated dark gray gray and and gray-green slates, argillites, graygreen slates, argillites,graywacke graywacke and and impure impure quartzite. quartzite. CharacterCharacter­ istically, the istically, the slates slates weather weather brownish brownish or or reddish. reddish. Tyler and (1952)described described the the Goose Goose Lake Lake iron-formation, iron-formation, Tyler and Twenhofel Twenhofel (1952) Its thickness which is aa magnetic which is magnetic member member of of the the Siamo Siamo formstion. formstion. Its thickness is is estimated estimated It extends for some the strike strike west at 50 at 50 to to 100 100 feet. feet. It extends for some distance distance along along the west and and northnorth­ The iron-formation is laminated, west of Goose Lake (Gair and Wier, 1964). west of Goose Lake (Gair and Wier, 1964). The iron-formation is laminated, The iron-formation iron-formation at magnetic, cherty, cherty, chloritic magnetic, chloritic and and sideritic. sideritic. The at the the St. St. to be be Goose 27 W. is though Lawrence pit in Section 5, 5, T. Lawrence pit in Section T. 47 47 N. N. ,, R 27 W.,, is though to Goose Lake, Lake, also. also. The Palmer gneiss The Palmer gneiss was was described described in in detail detail by by Lamey Lamey (1935). (1935). He He concon­ cluded that the the Palmer Palmer gneiss cluded that gneiss represented representedmetamorphosed metamorphosed (Animikie) (Animikie) sedisedi­ ments, formations, and ments, principally principally the the Ajibik Ajibik and and Siamo Siamo formations, and locally locally the the Mesnard Mesnard Monographs 28 and 52 describe the Palmer gneiss as and Kona Kona formations. formations. Monographs 28 and 52 describe the Palmer gneiss as and aa belt belt of of Laurentian Laurentian rocks, rocks, with withthe thecomment comment that thatT'phases "phases of of it it look look like like metameta­ Future mapping may clarify these relationships. morphosed sediments. morphosed sediments." Future mapping may clarify these relationships. The Negaunee Negauneeiron-formation iron-formation isis the the most The most important important and and interesting interesting member of of the the entire entire column, column, as as itit is member is the the host host rock rock for for most most of of the the iron iron ores. ores. In general, general, itit isis similar In similartotoother otherAnimikie Animikie iron-formations iron-formations of of the the Lake Lake Superior Superior The maximum maximum stratigraphic stratigraphic thickness Region. Region. The thickness is is attained attained in in the the NegauneeNegaunee­ Ishpeming area where where itit exceeds 000 feet, feet, not including the the intrusive intrusive masses. masses. Ishpeming area exceeds 2, 2,000 not including It It is is remarkable remarkable also also for for its its relative relativelack lackof ofargillaceous argillaceous and and arenaceous arenaceous facies. facies. �23 The in this this summary. sum.m.ary. The lithology lithologyisis discussed discussed in in m.ore more detail detail later later in Baraga Group Baraga Group The Baraga Baraga Group Group consists consists of major members: The of two two m.ajor m.em.bers: the theGoodrich Goodrich and and the the The Goodrich Goodrichform.ation formation isis principally principally quartzite, quartzite, with Michigamme form.ations. formations. The Michigam.m.e with In m.ost most localities, localities, there interbedded argillites argillites and interbedded and conglomerates. conglom.erates. In there is is aa basal basal conglomerate m.ade made up up of of fragm.ents fragments of iron-formation. The conglom.erate of the the Negaunee Negaunee iron-form.ation. Negaunee-Goodrich contact contact isis reported reported to angular discordance, Negaunee-Goodrich to have have up up to to 150 150 angular discordance, but com.m.only commonlythere there isis little little noticeable but noticeable discordance. discordance. Overlying the the Goodrich Goodrichquartzite quartzite isis the the thickest thickest member Overlying m.em.ber of of the the entire entire Animikie Series, the exceeds 5,000 Anim.ikie Series, the Michigamme Michigam.m.e formation form.ation which which probably probably exceeds 5,000 feet. feet. It is is distinctive also in It distinctive also in its its areal areal extent, extent, not not only only in in the the Marquette Marquette District, District, but but over much of the the central central part over m.uch of part of of the the Upper Upper Peninsula. Peninsula. Near the the base base of formation isis aa thin sub-member, Near of the the Michigamme Michigam.m.e form.ation thin magnetic m.agnetic sub-m.em.ber, termed the term.ed the Greenwood Greenwood formation form.ationby bySwanson Swanson and and Zinn Zinn (1930). (1930). Most Most of of the the The Clarksburg pyroclastics Michigamme is slate, argillite and graywacke. Michigam.m.e is slate, argillite and graywacke. The Clarksburg pyroclastics are found are found in in the the lower lower portion portion of of the the Michigamme Michigam.m.e where where they they occupy occupy an an The Bijiki ironasymmetrical position in the synclinorium (see Figure 4). asym.m.etrical position in the syncli norium. (see Figure 4). The Bijiki iron­ formation is the middle form.ation is found found above above the m.iddle member m.em.ber of of the the Michigamme. Michigam.m.e. It It extends extends from north north of Humboldt, at at the the Bessie Bessie Mine, from. of Hum.boldt, Mine, to to west west of of Three Three Lakes. Lakes. Over Over million tons tons of of iron iron ore from mines 44 m.illion ore have have been been produced produced from. m.ines in in the the Bijiki. Bijiki. the U.S.G.S. Harold Jam.es James (1958) Harold (1958) in in the U.S.G.S. Professional Professional Paper Paper 314-C, 314-C, the Paint describes the Paint River River Group Group that that overlies overlies the the Michigamme Michigam.m.e formation. form.ation. the southwest southwest of the Marquette Marquette Mineral These rocks are These are found found to the of the Mineral District. District. In In the past, past, som.e some geologist iron-formation with the geologist have have correlated correlated the the Bijiki Bijiki iron-form.ation with the River-Crystal Falls iron-formation of Riverton iron-form.ation of the the Iron Iron River-Crystal Fallsiron irondistricts. districts. This This would m.ean mean that that part part of formation would would be be in in the the Paint Paint River would of the the Michigamme Michigam.m.e form.ation River Group. Group. Granite is Granite is the the principal principal rock rocktype type along along the the south southlimb lim.bof ofthe the Animikie Anim.ikie There are thought to be both pre-Animikie and post-Animikie synclinorium. synclinorium.. There are thought to be both pre-Anim.ikie and post-Anim.ikie Goldich determ.ined determined an an age age of of 1,900 1,900 m.illion million years years on granites. Goldich granites. on one one sample sam.ple south of of Republic, Republic, and and 1,600 1, 600m.illion millionyears years on onanother. another. Some south Som.e students students believe believe that aa portion the granite-appearing that portion of of the granite-appearing rocks rocks were were formed form.ed by by granitization granitization of of sediments. pre - existing Animikie pre-existing Anim.ikie sedim.ents. Seaman (1944) suggested periods Seam.an (1944) suggested periods of of orogeny orogeny following following Michigamme Michigam.m.e time tim.e which he called the Sibley and Superior or Republic, preceding Keweenawan which he called the Sibley and Superior or Republic, preceding Keweenawan This would correspond to time. This tim.e. would correspond to the the Penokean Penokean (Goldich (Goldich et et al, aI, 1961) 1961) and and may m.ay be the be the time tim.e of of the the post-Animikie post-Anim.ikie granites granites and and the the deformation deform.ation of of the the Marquette Marquette Range synclinorium.. synclinorium. Range �I I 24 intrusive masses found within the has been been made Reference has Reference made above aboveto to the the intrusive masses found within the but are These intrusives Negaunee Negaunee iron-formation. iron-formation. These intrusives are are irregular irregular in in shape, shape, but are rather than as diorite They are described as as metadiabse metadiabse rather often sill-like. often sill-like. They are best best described than as diorite Locally, the sills have been publications. greenstone, as used in earlier or greenstone, as used in earlier publications. Locally, the sills have been of recognized primary differences in used as as horizon markers in used horizon markers in the the absence absence of recognized primary differences in these intrusives may be has been It has the Negaunee. It been suggested suggested that that the the age age of of these intrusives may be Possibly they might be related to the Clarksburg or or Keweenawan. Keweenawan. Possibly either Clarksburg either they might be related to the of these sillIt has also been suggested that that one one or or more more of Penokean orogeny. Penokean orogeny. It has also been suggested these sill­ indicate that bulk of the structural features like masses is extrusive, but the like masses is extrusive, but the bulk of the structural featull!es indicate that of some 700 feet. A They reach maximum thickness they are are intrusive. intrusive. They reach aa maximum thickness of some 700 feet. A of 400 400 feet. general average average would order of general would be be of of the the order feet. both the pre-Animikie and other intrusives intrusives are Various other are found found cutting cutting both the pre-Animikie and fine-grained mafic and andfelsic felsic dikes, dikes, others are Animikierocks. rocks. Some are fine-grained mafic Animikie Some are others are metapyroxenite and metagabbro. Some dikes medium toto coarse-grained coarse-grained meta-pyroxenite and metagabbro. Some dikes are medium are Locally they may be inversely and texture. fresh diabases, both in compoiti.on fresh diabases, both in composItion and texture. Locally they may be inversely polarized magnetically. polarized magnetically. sandstone are found south of Marquette. Exposures of Exposures of Jacobsville Jacobsville Cambrian Cambrian sandstone are found south of Marquette. friable sandstone with some conglomerate Typically, the Jacobsville is reddish, Typically, the Jacobsville is reddish, friable sandstone with some conglomerate are found, too, in the Gwinn and reddish reddish shale. shale. Some and Some sandstones sandstones exposures exposures are found, too, in the Gwinn the Ordovician rocks. Through all Still further District. Still further south south is is the the onlap onlap of of the Ordovician rocks. Through all of the recent Quaternary surficial material of the the district, district, variable of variable amounts amoun~s of the recent Quaternary surficial material of glacial glacial origin. are found, are found, principally principally of origin. (see Figure 4) has been compared to The column column in in the the Gwinn District (see Figure 4) has been compared to The Gwinn District Allen (1914): the principal synclinorium, and the principal synclinorium, and is is summarized summarized as as follows follows from from Allen (1914): Ordovician Ordovician Cambrian Cambrian Paleozoic Paleozoic Keweenawan Keweenawan Late Late Baraga Baraga j s:: n:l ..... 1-4 ~n:l uU Q) Middle Middle 1-4 O-i Early Early Menominee Menominee Limestones and sandstone Limestones and sandstone Intrusives Intrusives Princeton Series Princeton Series Ferruginous slate, cherty Ferruginous slate, cherty quartzite and graywacke quartzite and graywacke conglomerate conglomerate Gwinn Series Gwinn Series Dark gray slate, graywacke Dark gray slate, graywacke Iron-formation Iron-formation Dark gray to graphitic slate Dark gray to graphitic slate arkose and conglomerate arkose and conglomerate Granite, greenstone Granite, greenstone �• • 25 25 Some geologist geologist have have considered considered the the iron-formation iron-formation in District Some in the the Gwinn Gwinn District the Michigamme formation. as correlative to the Bijiki iron-formation in as correlative to the Bijiki iron-formation in the Michigamme formation. Metamorphic Metamorphic Zones Zones Studies have have been been made made on the metamorphic Studies on the metamorphic zones zones in in the the Upper Upper Peninsula. Peninsula. The area Particularly noteworthy Particularly noteworthy is is the the study study of of James James(1955). (1955). The area around around Republic Republic and the Republic Trough is shown on his maps to be of the highest intensity, and the Republic Trough is shown on his maps to be of the highest intensity, in in metamorphic intensity the the sillimanite sillimanite zone. zone. The The metamorphic intensity in in the the balance balance of of the the Marquette Marquette The Ishpeming-Negaunee Ishpeming-Negaunee extremity extremity of Iron Range Rangedecreases decreases to to the the east. east. The Iron of the the The metamorphic isograd6 cross producing district is in the chlorite zone. producing district is in the chlorite zone. The metamorphic isograds cross the the This suggests geologic structures structures at angles in in many areas. This geologic at high high angles many areas. suggests that that the the metameta­ morphism isis post-structure. post-structure. morphism Of considerable considerable interest interest is Of is the the paper paper by by James Jamesand andClayton Clayton (1962) (1962) relating relating mineral formation temperatures to their oxygen isotope fractionization. mineral formation temperatures to their oxygen isotope fractionization. Some Some samples from from the Range were were tested, tested, specifically samples the Marquette Marquette Range specifically from from the the Athens Athens They tentatively tentatively conclude: and Greenwood Greenwood Mines Mines and and the the Republic Republic district. district. They and conclude: (1) on on the the basis basis of of internal internal consistency and consistent consistent relations (1) consistency and relations to to the the mineralogic mineralogic evidence of metamorphic zoning, the isotopic data yields at least a fair evidence of metamorphic zoning, the isotopic data yields at least a fair approxapprox­ imation of of temperatures temperatures of imation of metamorphism metamorphism through through the the garnet garnet zones; zones; (2) (2) the the 2000 temperature of metamorphism for the chlorite zone reaches zpproximately temperature of metamorphism for the chlorite zone reaches zpproximately 200 0 that of and that of the the biotite biotite zone that of C. , that C., zone approximately approximately 275° 275 0 C. C.,, and of the the garnet garnet zone zone 0 (3) the approximately 3350°C. approximately 50 C. ;; (3) the rocks rocks in in the the staurolite staurolite and and sillimanite sillimanite zones zones (upper part part of amphibolite facies facies and and amphibolite amphibolite facies, facies, respectively) (upper of the the epidote epidote amphibolite respectively) 0 the present and the 350°C. were formed at temperatures were formed at temperatures above above 350 C., and present isotopic isotopic composition composition of the oxygen of these rocks is due to retrograde equilibration during temperature of the oxygen of these rocks is due to retrograde equilibration during temperature , decline. decline. Nome nc1atur e Nomen.clature From the until 1949 little From the time time of of the the publication publication of of Monograph Monograph 52 52 in in 1911 1911 until 1949 little change occurred in the petrographic nomenclature of the Marquette Mineral change occurred in the petrographic nomenclature of the Marquette Mineral that time, District. At District. At that time, The The Cleveland-Cliffs Cleveland-Cliffs Iron IronCompany Company undertook undertook aa sweepsweep­ ing revision revision of of many many ofofits its rock rock names. names, Numerous ing Numerous old old or or ambiguous ambiguous terms terms names had replaced with with modern modern or or more more precise were replaced were precise terms. terms. Various Various names had been been past; at used for the iron-formation iron-formation in used for the in the the past; at this this time, time, the the term termrtjrofl rtiron formationt'r -formation rr of des description was adopted adoptedasas the the sole sole name. name. A was A uniform uniform system system of cription was was effected effected also.. also �I 26 I rrsoft ore jaspertr previously used were The terms terms "hard 'hard ore The ore jasper" jasper rr and and rrsoft ore jasper rr previously used were and Republic Mine are Our beneficiating beneficiating plants eliminated. Our eliminated. plants at at the the Humboldt Humboldt and Republic Mine are processing rtjasper or taconitetT; sometimes referred referred to to in in the the press press as sometimes as processing ttjasper fY or rrtaconite"; ,iron_formationrrr is is preferred. however, the however, the expression expression "iron-formation preferred. Primary Primary Iron-Formation Iron-Formation I Sedimentary Facies of Iron- The summary summary of The of James James (1954) (1954) on on the the Sedimentary Facies of Iron­ sulphide, silicate and Formation emphasized emphasized the the four four facies: fades: carbonate, Formation carbonate, sulphide, silicate and Boyum_AndersonHan (1955) (1955)Primary PrimaryFeatures Other references references are are Boyum-Anderson-Han oxide. Other oxide. Features Relationship and Anderson-Han (1956) The of the the Negaunee Iron-FormatiOn and Anderson-Han (1956) The Relationship of Negaunee Iron-Formation; and Secondary Oxidation to the Concentrating of Diagenesis, Diagenesis, Metamorphism of Metamorphism and Secondary Oxidation to the Concentrating of the the Marquette Range. The Characteristics of Iron-Formation of Characteristics of the the Negaunee Negaunee Iron-Formation Marquette Range. The of been the principal primary constituent carbonate facies carbonate facies is is thought thought to to have have been the principal primary constituent of remnant Plate 1-A the Negaunee iron..formation, Plate the Negaunee iron-formation. I-A illustrates illustrates an anunoxidized unoxidized remnant James (1954 pages 258 et seq.), iron-formation. of typical typical cherty of cherty carbonate carbonate iron-formation. James (1954 pages 258 et seq.), oxide fades (as hematite) in the upper advances arguments arguments for for the advances the primary primary oxide facies (as hematite) in the upper The summary summary byStone and Qimberlidge part of iron-formation. The part of the the Negaunee Negaunee iron-formation. by S tone and Glmberlidge suggests that both hematite and magnetite (1964) on on the the Groveland Groveland Mine (1964) Mine geology geology suggests that both hematite and magnetite he believes is (1962) has has found found some some magnetite were primary. primary. Han were Han (1962) magnetite which which he believes is places in iron-formation. primary oxide facies in in several primary oxide facies several places in the the Negaunee Negaunee iron-formation. sulphides and and silicates silicates from the Marquette Specific illustrations illustrations of primary sulphides Specific of primary from the Marquette Range are are not Range not readily readily available. available. I chioritic clastic iron-formation Plate I-B Plate I-B illustrates illustrates the the magnetitic magnetitic chloritic clastic iron-formation Tilden Mine in the southeast portion of the found at the Empire Mine and the found at the Empire Mine and the Tilden Mine in the southeast portion of the found on the Cascade Range. Cla.stic iron-formation iron-formation is is also Marquette Range. Marquette Range. Clastic also found on the Cascade Range. southeast of the synclinorium. This suggests suggests aa source This source to to the the southeast of the synclinorium. Alteration of the Iron-Formation Iron-Formation Alteration of the iron-formation has been by oxidation and The principal principal alteration alteration of The of the the iron-formation has been by oxidation and The average iron content of primary enrichment under enrichment under varying varying conditions. conditions. The average iron content of primary The average altered Negaunee ironironformation approximates iron-formation approximates 26% 26%. dried. dried. The average altered Negaunee iron­ Locally in in the the Negaunee area, the dried. Locally formation approximates Fe, dried. formation approximates 31% 31% Fe, Negaunee area, the A general increase in porosity is higher, higher, reaching reaching about about 35%, average is average 35%. A general increase in porosity accompanies the accompanies the alteration. alteration. frequently characterized enrichment has has occurred, occurred, it Where enrichment it is is most most frequently characterized iron oxides, primarily hematite and replacement of of the the primary primary chert by replacement chert by by iron oxides, primarily hematite and I �27 greater part goethite, and goethite, and locally locally magnetite. :magnetite. The The greater part of of this this alteration alteration has has been been volume-for-volume replace:ment replacement as as very very little volu:me-for-volu:me little slumping slu:mping has has been been noted. noted. In In numerous instances instances it from the nu:merous it is is possible possible to to follow follow the the primary pri:mary bedding bedding fro:m the ironiron­ The ore ore contacts formation into into the the ore. for:mation ore. The contacts frequently frequently cut cut the the bedding bedding at at high high angles. angles. The folding folding of of the the Marquette Marquette Range The Range synclinorium synclinoriu:m was was accompanied acco:mpanied by by the development of a strong joint system which increased the permeability the develop:ment of a strong joint syste:m which increased the per:meability of of Exploration and and :mining mining in in recent recent years the iron-formation. the iron-for:mation. Exploration years have have indicated indicated that both both oxidation oxidation and and enrich:ment enrichment extend extend toto far far greater greater depths that depths than than thought thought Numerous drill drill holes holes have have cut cut rich rich ore ore grade earlier. Nu:merous earlier. grade material :material to to depths depths of of term trorerr oretr isis used over 5, 000 feet feet fro:m from the the present present land over 5, 000 land surface. surface. The The ter:m used here here as as meaning high and does does not not neces necessarily imply an an econo:mic economic profit :meaning high iron iron content content and sarily i:mply profit hole on the Range was drilled drilled as the term is customarily. The the ter:m is defined custo:marily. The deepest hole on the Range was size, and and encountered encountered oxidation and enrichinch) size, depth of 365 feet, feet, NX NX (3 to aa depth of 6, 6,365 (3 inch) oxidation and enrich­ During late late Preca:mbrian Precambrian ti:me time when the alteration alteration may nay the bottom. ment to :ment to the botto:m. During when the have occurred, occurred, the greater. have the depth depth of of this this alteration alteration was was undoubtedly undoubtedly greater. Some parts parts of contain considerable considerable silicates silicates such So:me of the the Negaunee Negaunee contain such as as sericite, grunerite-cummingtonite, hornblende and garnet in the higher sericite, grunerite-cu:m:mingtonite, hornblende and garnet in the higher meta:meta­ morphis zones minnesotaite, :morphis zones (such (such as as at at Humboldt Hu:mboldt and and Republic); Republic); and and :minnesotaite, stilpnomelane and and chlorite chlorite in stilpno:melane in the the diagenetic diagenetic or or lower lower metamorphic :meta:morphic zones zones (such as as at at E:mpire). Empire). According or all all of of these these silicates silicates are (such According to to one one view, view, many :many or are derived by by the the :meta:morphis:m metamorphismofofearlier earlier pri:mary primary silicates. silicates. Others derived Others believe believe that that these silicates silicates are these are the the result result of of the the reaction reaction of of earlier earlier iron iron minerals :minerals (carbonate (carbonate and/or the silica and/ or oxides) oxides) and and the silica of of the the chert chert under under metamorphic :meta:morphic conditions. conditions. Plate I-C of the the silicates. silicates. Plate Plate I-C shows shows the the development develop:ment of Plate I-D I-D is is aa polished polished slab slab are photoof :magnetite magnetite carbonate carbonate silicate silicate iron-formation. of iron-for:mation. Plates Plates I-E I-E and and F Fare photo­ micrographs of the portions portions rich :micrographs of the the slab slab showing showing the rich and and lean lean in in magnetite, :magnetite. Ore Ore Occurrences Occurrences There There are four four general general types types of of ore orewhich which have have been been produced produced and and shipped are shipped They are: from the Marquette Iron fro:m the Marquette Iron Range. They are: High grade grade direct direct shipping shipping rrsoftu rrsoft tr ores, ores. High grade grade direct direct shipping "hardtttr ores, ores, High shipping "hard Siliceous ores, Siliceous ores, Concentrates and agglomerates (pellets) Concentrates and agglo:merates (pellets) from fro:m low low grade grade iron-formations. iron-for:mations. Traditionally in in the the Lake Lake Superior Superior Region, Region, the the direct direct shipping Traditionally shipping ores ores have have Recently, the direct natural (moisture aa base base iron iron content content of of 51.5% 51. 5% natural (:moisture included). included). Recently, the direct �1 J 28 28 I the competition of averaged 54% Fe, natural-, reflectingores ores have shipping have aof shipping ores have averaged 54% paid Fe, natural, reflecting competition for the hard lump the which premium is the foreign foreign ores. ores. AA premium Thea the isTheir paid average for the hard lump ores which have content is 61. 5%. iron inch -8 inch. range of +2 size size range of +2 inch -8 inch. Their average iron content 61. 5%. of The small isshipments specialty grade, constitutes siliceous type type of of ore, ore, aa specialty from siliceous grade, constitutes small shipments of which averages 38% Fe. The pellets range richer iron_formation richer iron-formation which averages 38% Fe. The pellets range from natural. 61 to to 65% Fe, natural. 61 65% Fe, between rrsoftrt For For made a distinction many years the miners have made a distinction between earthy many years the miners havesoft rrsoft" ores are porous, friable, "hard" ores. In generals the ores and and r'hard" ores ores. In general, the soft ores are porous, and martite friable, (locally earthy chiefly of hematite, semi_plastic and are made up to and to semi-plastic and are made upamounts of hematite, and martitechert, (locally of goethite unreplaced and with minor chiefly of still magnetite) The other still magnetite) and with minor amounts goethite, unreplaced chert, and through P). (see Plate III - M (mica, chlorite) locally silicates with low locally silicates (mica, chlorite) (see hard, Plate dense, III - M compact, through P). The other hard ores which are hard, extreme dense compact ext reme are are the the hard ores which are dense, compact, with low magnetite martite, The iron minerals are porosity. These ores form porosity. The iron minerals are magnetite, martite, T).dense compact specularite (see Plate III - Q through hematite, and would fall hematite, and specularite (see Plate III -ofQhigh through T).oreThese form grade minedores amount A substantial the lump "semi-hard" the lump product. product. A substantial amount of high grade oreasmined would fall Terms such these two end types. somewhere in between tonnageS of rr somewhere in between these two end orebodies, types. Terms such as "semi-hard substantial Locally in the soft been used. have been used. Locally in the soft orebodies, appearance have substantial tonnages of macroscopic found which are similar in "hard" ores have been "hard" ores have been found which are similar in in macroscopic appearance Plate III. of the hard ore mines, as shown to the the hard hard ores ores of to the hard ore mines. as shown in Plate III. Soft Ores Ores Soft total production of the Marquette Iron Range, per cent of the Seventy per gradeRange, direct Seventy cent of the total production the of Marquette been the high Iron and Gwinn Districts, has of including the Cascade in the basal including the Cascade and Gwinn Districts, has for been the high theofmost part,grade direct The ores occurred, shipping type of soft ore. be asinthick as shipping type of soft ore.iron_formation. The ores occurred, the most the basal Thesefor deposits maypart, of the Negaunee portion The lateral extent. portion of the Negaunee iron-formation. These deposits may be as thick as the bedding, and have considerable Z60 feet, feet, normal normal to 260 to the bedding, and have considerable lateral extent.bounded The and in fault structures found in the synclineS orebodies are generally north-south section lookorebodies are generally found in the synclines and in fault structures bounded along at least one side. Figure 6 is a by basic dikes Negaunee showing a by basic dikes along at least one side.side Figure is a of north-south section look­ of the6 City through the eastern ing west west passing passing through ing theineastern side of the City of Negaunee showing a this vicinity. variety of ore occurrences variety of ore occurrences in this vicinity. which are chimneys of Locally the soft ores are found in "ore pipes" of the ironLocally the soft ores are found incutting "ore pipes" which are chimneys of the stratification distance vertically, ore extending some and are ore extending some distance vertically, cutting the stratification of the iron­ ZOO to 300 feet across generals these ore pipes are In general, formation. In iron_formation. formation. theseofore are dikes 200 to cutting 300 feet and are theacross twopipes or more at the intersection localized phosphorus content localized at the intersection of two or more the iron-formation. alsodikes by itscutting low type of ore has been characterized This This type of ore has been characterized also by its low phosphorus content ground." and by "heavy "heavy ground. and by It the large intrusive sills The other major type of soft ore occurs on some sills of the The other major type of soft ore occurs on soft the large intrusive These ores were part of the iron_formation. near the upper distribution near the upper part of soft were some of the The ore is ores of irregular in the theiron-formation. Ishpeming area. These first to to be be exploited exploited in locality in which first theand Ishpeming area. The ore is of irregular distribution its thickness. The principal as to its occurrence both of the Ishpeming toward the axis both as to its occurrence and its the principal locality in which souths.of The orebodieS were found is to thicknes these these orebodies were found is to the south of Ishpeming toward the axis of the I I I I I I I �29 29 Marquette Range Range synclinorium. synclinorium. We Marquette We do do not not have have any any mines mines operating operating in in this this type of of are ore occurrence occurrence at type at this this time, time, although although around around the the turn turn of of the the century century It is is interesting this was an important important ore ore source. this was an source. It interesting to t01 note note that that these these soft soft structural ores, lying sheets, are ores, lying on on the the metadiabase metadiabase sheets, are limited limitedby by the the same same structural In general, general, the controls as controls as the the ore ore lying lying on on the the footwall footwall contact. contact. In the ores ores were were high in in iron high iron content content and and low low in in phosphorus phosphorus and and sulphur. sulphur. A sizable sizable tonnage of soft soft ore ore in A tonnage of in Ngaunee Negaunee is isimpregnated impregnatedwith with gypsum. gypsum. The gypsiferous ores analyses range 2 to Sulfur analyses Sulfur range from from0.0.2 to over over 3. 3. 0%. The gypsiferous ores occur occur at at cutting across the bedding of definite elevations (near the present sea level) definite elevations (near the present sea level) cutting across the bedding of iron formation. the ironthe Ores Hard Ores The hard hard ores of the the total total production The ores amount amount to to 20% 20% of production to to date. date. Most Most of of them are found in the uppermost portion of the Negaunee iron-formation and them are found in the uppermost portion of the Negaunee iron-formation and ores were immediately below the Goodrich formation contact. immediately below the Goodrich formation contact. The The ores were made made up up hematite, and of hard, hard, compact of compact to to specular specular hematite, andmagnetite magnetite(see (seePlate PlateIll). III). AccesAcces­ the ore may include include garnet garnet and sory minerals may and tourmaline. tourmaline. The The footwall footwall of of the ore iron-formation of !jaspilite?! may be be unoxidized unoxidized iron-formation, iron-formation, oxidized may oxidized iron-formation of the the" jaspilite" hanging wall wall may may consist consist of type, or the intrusive intrusive sills. sills. The type, or one one of of the The hanging of material material less commonly of the the Goodrich Goodrichformation, formation, oxidized oxidized iron-formation iron-formation or or - less commonly -­ of The orebodies orebodies are are frequently material. The intrusive material. intrusive frequently related related to to intrusive intrusive dikes. dikes. features are noted in the hard ores as well as in Replacement features are noted in the hard ores as well as in the Replacement the soft soft ores. ores. are frequently related to The outlines hard orebodies The outlines of hard orebodies are frequently related to structural structural features features as folds, folds, faults faultsand anddikes. dikes.Some Some hard hard ores ores are are also such as such also found found locally locally the soft soft orebodies. orebodies. near the base of of the theNegaunee Negaunee iron-formation, iron-formation, as near the base as aa part part of of the basal Goodrich material consists consists of conglomerates, argillites, The basal The Goodrich material of conglomerates, argillites, Locally a conglomerate may contain a sufficient slates and quartzites. slates and quartzites. Locally a conglomerate may contain a sufficient amount amount of ore, ore, either or the the matrix matrix material, of either in in the the form form of of pebbles pebbles or material, to to be be merchantable merchantable The intrusives intrusives which cut the the hard hard ore for mining. for mining. The which cut ore are are quite quite frequently frequently confused confused Both materials are fine-grained and highly with the the argillite argillite of with of the the Goodrich. Good'rich. Both materials are fine-grained and highly altered, making altered, making identification identification difficult. difficult. Presently there there are hard ore Presently are two two active active hard ore properties properties in in the the Range: Range: the the Cliffs Cliffs Shaft and andthe theChampicm ChampionMines. Mines. Former Former major now Shaft major hard hard ore ore properties, properties, now include the the Lake Lake Superior Superior Hard Hard Ore, inactive, include inactive, Ore, Humboldt, Humboldt, Republic, Republic, Michigamme Michigamme The Cliffs Shaft Mine structure is a westerly and Greenwood Mines. and Greenwood Mines. The Cliffs Shaft Mine structure is a westerlyplunging plunging The Greenwood syncline, having syncline, having a a cross-fold cross-foldunder underthe thetown town of of Ishpeming. Ishpeming. The Greenwood and Champion ChampionMines, Mines,by bycontrast, contrast, are and are located located on on the the south south limb limb of of the the synsyn­ These hard orebodies have a definite westward plunge and extend clinorium. clinorium. These hard orebodies have a definite westward plunge and extend At Republic Republic Mine Mine the the ores ores some distance distance below below the the present present land some land surface. surface. At were mined some 4, 4,000 feet along along the the plunge, plunge, or or 2,800 2,800 feet feet vertically. were mined some 000 feet vertically. �30 Concnetrating Ores Concnetrating Ores properties in Michigan was the the modern beneficiating The first of grade concentrates producing high in The first of the property modern beneficiating properties Michiganspecularitic was the has been This Humboldt Mine. consists of the The crude ore Humboldt Mine. This property has been producing high grade concentrates Concentration is and peUets since 1960. since 1954, Negaunee. since 1954, and pellets since 1960. consists of the specularitic theThe topcrude of theore iron-formation at production magnetic cherty having started magnetic cherty ironformation at the top of the Negaunee. Concentration is Mine is similar, Republic The and specularitic flotation. by froth the specularitic by froth flotation. The Republic Mine is similar, having started production L illustrate 1956. Plates II- K and Both Humboldt and Republic of pellets pellets in crude the ores. of iniron-formations 1956. Plates II· K and L illustrate specularitic and specularitic which are the magnetitic iron- formations whichofare magnetitic thegrade crudeores. ores. Both Humboldt and Republic high formerly producers were formerly Mines were Mines producers of high grade ores. silicate cherty ironmagnetitic carbonate mining a Concentration is iron-formation. The Empire Mine The Empire Mine is mining a magnetitic carbonate silicate cherty iron­ of the Negaunee lower section I, and J H, formation in the lower and Plates II-G, formation in theseparation. section of the Negaunee iron·formation. Concentration Plates I-D, E and F, is by is by magnetic magnetic separation. Plates I-D, E and F, and Plates II-G, H, I, and J illustrate some of this crude ore. illustrate some of this crude ore. Genesis of the_High Grade Ores Genesis of the High Grade Ores on the origin of the high grade universal agreement There has been no also, regarddifference in opinion, There are There has beenIron no universal agreement on the ongm of the high Range. opposed hard ores as grade the Marqiette ores of enrichment of the ores of the Marquette Iron Range. There are difference in opinion, also, regard­ timing of the and the ing both the method and discussed first. ing both the method the timing of the enrichment of the hard ores as opposed The soft ores are to the the soft ores. The to soft ores. soft ores are discussed first. Soft Ores hypotheses of the origin of the soft to most are common Certain features Soft Ores ores: ores: Certain features are common to most hypotheses of the origin of the soft iron-formation was important in permitting Fracturing of the silica and 1. iron-formation, to remove primary 1. Fracturing of the ironformation was important in permitting oxidize the access for water to of the silica. to remove silica and much access for water to oxidize the primary ironformation, the iron which replaced to transport to transport the iron which replaced much of the silica. solutions that removed presumably by the same have been The silica was silica 2. remnants of theby removed 2. The silica was removed presumably the same carried solutions that Inasmuch as no to the carried the iron. Inasmuch as no remnants that it was it is assumed carried the iron. Marquette of the removed silica have been Range, identified on the identified on the Marquette Range, it is assumed that it was carried to the ancient surface. ancient surface. and Bijiki ironfound only in the Negaunee The orebodies are altered and en3. mayNegaunee have been in the column 3. The orebodies are found only in the and iron­ found has been formations. Other rock types tonnage of high grade soft oreBijiki formations. Other rock types in the column may have been altered and en­ but no significant riched locally, numbers. riched locally, but geologic no significant tonnage of high grade soft ore has been found other in any of the in any of the other geologic numbers. the and on found lying on the Siamo footwallThese orebodies are less The soft uopen_facinght structures. 4, or 4. The soft orebodies are found lying on the Siamo footwall and on the in trough-like" metadiabase sheets metadiabase sheets in "trough-like" or "open-facing 11 structures. These less — �• • 31 31 permeable members members may may be be folded foldedandlor and/or faulted, faulted, but but appear appear to to act act as as "bottom" 'bottom" permeable surfaces. surfaces. major structural 5. The major structural controls controls of of folding, folding, faulting faulting and and most most intrusives intrusives Some intrusives and, according to to some some observers, were pre-ore. were pre - ore. Some intrusives are post-ore and, observers, faulting and and possibly possibly some some of of the the folding folding are are post-ore. some faulting post-ore. Few of of the the deeper deeper major Few major orebodies orebodies extend extend to to ledge ledge surface surface up up the the dip dip or up or up the the pitch, pitch, but but the the oxidation oxidation of of the the iron-formation iron-formation adjacent adjacent to to the the orebodies orebodies definitely does definitely does extend extend to to ledge. ledge. 6. Any hypotheses must must account account for for the 7. Any hypotheses the circulation circulationof ofa. a. hydraulic hydraulic system which extends to to depths depths of of over over 6, 000feet feet from from present present surface. system which extends 6, 000 surface. Most soft soft ores ores contain amounts of of clay clay mineral mineral assemblages 8. Most contain varying varying amounts assemblages that temperatures higher that indicate indicate temperatures higher than than normal normal ground-water ground-water temperatures. temperatures. The relations relations of these clay minerals to The of these clay minerals to the the iron iron minerals minerals is is not not conclusive. conclusive. They are are not They not established established as as definitely definitely contemporaneous. contemporaneous. Cold Water Origin Cold Water Origin Monograph28 28reviewed reviewedthe thevariolJ.s varioiis ideas ideas of of soft soft ore Monograph ore origin origin and and advanced advanced agent of of oxidation, oxidation, solution solution of of silica, silica, and the basic basic cold the cold water water hypothesis. hypothesis. The The agent and The iron which replaced introduction of of iron iron was was oxygen-bearing oxygen-bearing ground-waters. ground-waters. The iron which replaced introduction In 1935, the silica silica was the was derived derived from from other other portions portions of of the the iron-formation. iron-formation. In 1935, C. C. K. K. Leith et Leith et al al (pages (pages 2424- 26), 26), modified modified the the hypothesis hypothesis by by proposing proposing that that the the chemical chemical activity of the circulating circulating ground-waters activity of the ground-waters had had been been increased increased by by heating heating due due to to They also observed that oxidation is found Keweenawan lavas and intrusives. Keweenawan lavas and intrusives. They also observed that oxidation is found at at greater depth be expected expected of of normal normal ground-water ground-water circulation greater depth than than would would be circulation even even under under mountainous mountainous conditions. conditions. Hydrothermal Origin Hydrothermal Origin In 1926, J. W. In 1926, J. W. Gruner Gruner proposed proposed aa hydrothermal hydrothermal origin origin for for Vermilion Vermilion Iron Iron In 1929 he extended extended this this hypothesis hypothesis to to the Range ores. ores. In Range 1929 he the formation formation of of high high grade grade Gruner's hypothesis stressed the ores throughout the Lake Lake Superior Superior region. ores throughout the region. Gruner's hypothesis stressed the The thermal conditions would greater dissolving hot water water on on silica. silica. The thermal conditions would greater dissolving power power of of hot Objections were were raised raised to stimulate hydraulic stimulate hydraulic circulation. circulation. Objections to the the idea idea that that these these waters were juvenile on the basis that most of the Lake Superior intrusives waters were juvenile on the basis that most of the Lake Superior intrusives were were his "modified theory' basic and and therefore thereforerelatively relatively"dry". 'dry'. In basic In 1937, 1937, he he published published his "modified th eory ll which proposes that the ore-forming fluids were principally meteoric waters which proposes that the ore-forming fluids were principally meteoric waters which had hadbeen beenheated heatedby byigneous igneousemanations. emanations. He also0 that which He conceded conceded als that not not all all of of Gruner explained the observed the introduced iron came from these emanations. the introduced iron carne from these emanations. Gruner explained the observed differences in in resultant resultant ore differences ore types types as as being being related related to to differences differences in in primary primary ironiron­ formation, structural formation, structural conditions, conditions, temperatures temperatures of of the the water, water, and and relative relative quantities quantities of of emanations. emanations . �32 Summary on Soft Ore Ore Genesis Summary on Soft Genesis dissimilar. Aside from The theories theories of Gruner are are not The of Leith Leith and and Gruner not too too dissimilar. Aside from is almost the same, the Gruner's "emanations," the ore-forming process Gruner's "emanations," the ore-forming process is almost the same, the The geometry of the soft orebodies differences being only aa matter matter of differences being only of degree. degree. The geometry of the soft orebodies complicated plumbingH of the hydraulic systems. is significant in stressing stressing the is significant in the complicated "plumbing" of the hydraulic systems. Some the "open" "open' side structural traps. Many of of the the orebodies orebodies are are found Many found on on the side of of structural traps. Some surface. have no no apparent apparent relationship relationship to have to the the present present surface. Recent microscopic work by also. Recent microscopic work by The mineralogy The mineralogy may may be be significant significant also. in the the soft soft ores, ores, as shown in Plate Tsu-Ming Han has has found found appreciable appreciable martite martite in TsuMing Han as shown in Plate soft orebodies are essentially The semi-hard 0 and III. a III. and P. P. The semi-hardores oresfound found in in the the soft orebodies are essentially contains traces traces to appreciable martite, some some of which contains up of equigranular martite, made up made of equigranular of which to appreciable martitization was contemporaneous remnants, Han magnetite remnants. magnetite Hansuggests suggeststhat that the the martitization was contemporaneous the soft with the soft ore are formation. formation. clay minerals suggest temperature Lastly, as Lastly, as pointed pointed out out above, above, some some of of the the clay minerals suggest temperature The writer noted dickite and chrome higher than those of normal ground-waters. higher than those of normal ground- waters. The writer noted dickite and chrome in 1945, as described by Gruner (1946). nontronite in in the ores in nontronite the Marquette Marquette Range Range ores 1945, as described by Gruner (1946). (non-definitive), (l96Q)describes describes dickite, dickite, kaolinite The paper paper by Bailey and The by Bailey and Tyler Tyler (196P:L kaolinite (non-definitive), clinochrysotile, muscovite, lizardite, lizardite, clinochrysotile, nacrite, talc, nacrite, talc, pyrophyllite, pyrophyllite, 1M 1M and and 2M1 2M 1 muscovite, trioctahedral chlorite, dioctahedral and trioAl-serpentine, dioctahedral AI-serpentine, dioctahedral and and trioctahedral chlorite, dioctahedral and trio­ and regular inter stratifications of ctahedral montmorillonite, skite, and regular inter stratifications ctahedral montmorillonite, palygor palygorskite, of non-clay minerals apatite, alunite, chloritemontmorill0flite, as chlorite-montmorillonite, as well well as as the t'he non-clay minerals apatite, alunite, and Tyler state on pages 155 and rhodochrosite. Bailey gypsum, clacite, clacite, and gypsum, and rhodochrosite. Bailey and Tyler state on pages 155 and by field data and 156, "In "In summary, summary, both 156, both the the synthesis synthesis data and the the evidence evidence provided provided by- field in the world suggest that the clay relationships for for similar relationships similar clays clays elsewhere elsewhere in the world suggest that the clay is primarily the result of hydromineral assemblage iron ores mineral assemblage in in the the Michigan Michigan iron ores is primarily the result of hydro­ intimate association of the clay minerals with the . The intimate . . thermal activity. thermal activity. The association of the clay minerals with the differences may also extend to the origin of the ore ore suggests these differences iron are iron suggests that that these may also extend to the origin of the ore itself.''II itself. chlorite zone of metaAs noted As noted earlier, earlier, the the soft soft ores ores are are found found in in the the chlorite zone of meta­ morphism. morphism. Hard Ores Hard Ores the soft ores. There may be two hard ores ores are are more more complex The hard The complex than than the soft ores. There may be two Significant features are: origin and and times times of formation. or more more modes or modes of of origin of formation. Significant features are: 1. formation. 2. 2. under less under less 200 feet of the Negaunee ironThe hard upper 200 The hard ores ores are are found found in in the the upper feet of the Negaunee iron­ the Goodrich contact. Most commonly, the hard ore is at Most commonly, the hard ore is at the Goodrich contact. such as anticlinal flexures, The hard The hard ores ores are are in in 'closed" ilclosedll structures, structures, such as anticlinal flexures, permeable rocks. permeable rocks. �33 33 3. Common ly, the adjacent to ore is is the the "oxide"oxide­ 3. Commonly, the iron-formation iron-formation adjacent to the the ore facies" jaspilite, the reddish, pinkish pinkish banded banded chert the miners miners once once called called facies" -- jaspilite, the reddish, chert the "hard "hard ore ore jasper." jasper." 4. Hard ores tend to little to to no no Hard ores tend to have have equigranular equigranular iron iron minerals, minerals, little porosity, few vugs vugs and and no porosity, few no botryoidal botryoidal textures. textures. The magnetite magnetite ores ores are masses in 5. The are commonly commonly in ln discontinuous discontinuous masses in specularitic iron-formation specularitic iron- formation and and ore, ore. The The chert chert associated associated with with magnetite magnetite ore ore is gray In some some areas areas magnetite is gray rather rather than than reddish. reddish. In magnetite orebodies orebodies and and magnetitic magnetitic iron-formation traversed by by quartz quartz veins veins containing containing tourmaline, very coarse coarse iron-formation are are traversed tourmaline, very specularite and crystalline siderite specularite and crystalline siderite with with minor minor pyrite, pyrite, sphalerite sphalerite and and chalcopyrite. chalcopyrite. Frequently the 6. Frequently the hard hard ores ores extend extend down down into into the the iron-formation iron-formation as as "droppers,"" appearing "droppers, appearing to to have have been been formed formed by by replacing replacing the the iron-formation. iron- formation. Locally, at contact, some 7. Locally, at the the Goodrich Goodrich contact, some massive massive hard hard ore ore contains contains detrital quartz which suggests that the original iron minerals may have detrital quartz which suggests that the original iron minerals may have had had a a similar detrital similar detrital origin. origin. Above the the hard hard ores ores and 8. Above and at at the the base base of of the the Goodrich, Goodrich, one one finds finds conglomerates of conglomerates of varying varying thickness. thickness. The The conglomerate conglomerate may may contain contain much much detrital detrital chert or chert or quartz, quartz, and and some some ore ore fragments fragments that that appear appear to to have have been been ore ore at at the the time time of deposition. deposition. of Dynamic metamorphism metamorphism has has been been responsible responsible for 9. Dynamic for the the formation formation of of the the specular hematite in the ores and adjacent iron-formation. specular hematite in the ores and adjacent iron-formation. 10. 10. No hard hard ore ore is in the the Bijiki Bijiki iron-formation. No is found found in iron-formation. Hypotheses of of Hard Hard Ore Ore Origin Hypotheses Origin Monograph 52, 52, pages pages 278278-279, Monograph 279, outlines outlines a a possible possible origin origin and and time time sequence sequence upper portion portion of iron-formation was The upper of ore ore formation. of formation. The of the the Negaunee Negaunee iron-formation was exposed exposed to weathering weathering and and concentration concentration (mechanical (mechanical classification?) classification?) to to to produce produce an an iron iron Burial by rich product. rich product. Burial by the the Goodrich Goodrich and and later later formations formations followed. followed. After After the the deposition of of the the Michigamme Michigamme formation, formation, the deposition the Animikie Animikie sediments sediments were were folded, folded, The metamorphism metamorphism associated associated with with the the structural structural deformafaulted and faulted and intruded. intruded. The deforma­ tion formed formed the the hard hard ores ores from tion from the the weathered weathered ores. ores. re-exposed the iron-formaPost-Keweenawan erosion re-exposed Post-Keweenawan the Negaunee Negaunee and andBijiki Bijiki iron-forma­ They were altered by ground-waters to form the soft ores, as outlined They were altered by ground-waters to form the soft ores, as outlined ores were earlier. Since the the soft soft ores were formed formed after after the the dynamic dynamic metamorphism, metamorphism, they they do not not display display the the specular specular hematite hematite and the hard hard ore. do and other other features features of of the ore. tions, tions. �J.' 34 I I The objection concept centers on on the the trweathered_surfaceu "weathered-surfacer! origin ongln objection to to this this concept for the hard necessary to to postulate postulate some some introduction introduction of of iron for all of the hard ores. It It is necessary to explain both of many many hard orebodies. orebodies. to explain both the the geometry geometry and and detailed detailed features features of This introduction of of iron must have have been been accomplished accomplished before or during during metameta­ This introduction iron must before or morphism. morphism. The school of of thought thought would much of The hydrothermal school wouldascribe ascribe much of the the hard ores to replacement of the iron-formation by high high temperature solutions. to temperature solutions. An Alternate Time Time Sequence Sequence The by the mining mlnlng companies, companies, and and the The continuing continuingresearch research each year year by mapping by Geological Survey, add materially to to our our informainforma­ current mapping by the the U. U. S. S. Geological Survey, add tion More age-dating age -dating will will be be done done to to tion on on the the geology geology ofofthe the Marquette MarquetteRange. Range. More help time - sequences of of ore-formation. The The writer that aa help establish establish time-sequences writer believes that better understanding of the Clarksburg Clarksburg better understanding of the the relationship relationship of of the the metadiabases, metadiabases, the pyroclastics and the Penokean Penokean orogeny pyroclastics and orogeny will willalter alter the the classic classic time-sequence. This understand the the effects effectsof ofKeweenawan Keweenawan vulcanism. vulcanism. This will help us understand Other Ores of of Economic Economic Interest Other Interest Numerous gold, silver and and lead lead prospects prospects have have been been noted noted north north of of Numerous gold, silver Ishpeming The age of the is Ishpeming inin the the Pre-Animikie Pre-Animikie series. series. The age of the mineralization is thought M. Broderick Broderick(1945) (l945) who who described des cribed thought to to be be post-middle post-middle Animikie Animikie by by T. T. M. the gold occurrence occurrence at at the the Ropes Ropes Gold Gold Mine. Mine. AAtotal totalofof$703, $703,000 000 was was the major gold recovered this operation operation during during the the period periodof of1883 1883 to to 1897. 1897. recovered from this Significant amounts iron­ Significant amounts of of uranium uranium oxide oxide have have been been detected detected in in the the ironformation on the Marquette Marquette Range Range and and in in the the Gwinn Gwinn District. rich formation on District. ThoriumThorium-rich monazite noted in Goodrich quartzite and conglomerate conglomerate of of the the monazite has has been noted in the Goodrich quartzite and Cascade District, Cascade Vickers (1956). (l956). District, as as described described by Vickers Acknowledgment Grateful acknowledgment acknowledgment is Grateful is made colleagues in in The The made to to the the writer's writerts colleagues Cleveland-Cliffs Iron Company, Cleveland-Cliffs Company and and Laughlin Laughlin Company, Inland Inland Steel Steel Company and Jones Jones and Steel Corporation, and Steel and their their managements, for assistance assistance in in preparing preparing this managements, for summary. The summary. The writer writerparticularly particularlyappreciates appreciatesthe thecooperation cooperationand and contributions contributions by the the U. by U. S. S. Geological Geological Survey Survey and and the the Michigan Michigan Geological Geological Survey. Survey. Special I ~ II I I I I I I I I J J J �35 thanks are are due to Dr. Dr. Jacob thanks due to Jacob Gair. Gair. SELECTED SELECTED B]BLIOGRAPHY BIBLIOGRAPHY Adler, Joseph Adler, Joseph L., L., (1935), (1935), "Stratigraphic "StratigraphicZones Zones in inthe theNegaunee Negaunee Iron-Formation Iron-Formation of Marquette Marquette County, County, Michigan" Michigan" The The Journal Jburnal of of of Geology, Geology, Vol. Vol. XLIII, XLIII, pp. 113-132 pp. "Correlation and and Structure Structure of of the the Precambrian Precambrian Forma­ FormaR. C. (1914), "Correlation Allen, R. C.,, (l914), tions of Iron Bearing Bearing District tions of the the Gwinn Gwinn Iron Districtof ofMichigan" Michigan" Journal JournalofofGeology, Geology, Vol. XXII, pp. 560573 Vol. XXII, pp. 560=573 Anderson, Anderson, G. G. J. J. and andHan, Han, Tsu-Ming, Tsu-Ming,(1956), (l956), "The "TheRelationship Relationship of of Diagenesis, Diagenesis, Metamorphism, and to the the Concentrating Concentrating Character­ CharacterMetamorphism, and Secondary Secondary Oxidation Oxidation to istics of the Negaunee Iron-Formation of the Marquette Range" istics of the Negaunee Iron-Formation of the Marquette Range" Geological Geological Exploration pp. 63-69, 63-69, Institute Exploration (MCM&T) (MCM&T) pp. Institute on on Lake Lake Superior SuperiorGeology Geology "Mineral Notes (1940), "Mineral Ayres, V. Ayres, V. L. L.,, (l940), Notes from from the the Michigan Michigan Iron Iron Country" Country" The American American Mineralogist, Mineralogist, pp. The pp. 432-434 432-434 S. W. and Bailey, S. Bailey, and Tyler, Tyler, S. S. A., A., (1960), (l960), "Clay "Clay Minerals Minerals Associated Associated with with the the Geology, Vol. Vol. 55, Superior Iron Iron Ores " Economic Lake Superior Ores" Economic Geology, 55, pp. pp. 150-175 150-175 Boyum, Burton Burton H., H., (1945), Boyum, (1945), "Geological "Geological Exploration Exploration on on the the Marquette Marquette Range" Range" Mining CongressJournal, Journal, pp. Mining Congress pp. 29-33, 29-33, 36 36 Boyum, Burton Burton H., H., (1954), the Marquette Marquette Iron Iron Range~' Range' Boyum, (l954), "The "The Geology Geology of of the Fourth Mining GeologySymposium, Symposium,University University of of Minnesota, Minnesota, pp. pp. 3-8 Fourth Mining Geology 3-8 G. J.., "Primary Features Anderson, G. Boyum, B. B. H. Boyum, H.,, Anderson, J., and and Han, Han, T-M, T-M, (1955), (l955), "Primary Features of the the Negaunee Iron-Formation" Fifth of Negaunee Iron-Formation" FifthMining MiningGeology Geology Symposium, Symposium, University University of of Minnesota Minnesota Geology of of the the Marquette Marquette Iron Boyum, Burton Boyum~ Burton H. H. (1962), (1962), "The Geology Iron Range" Range" Geology of the the Lake Lake Superior Superior Region, Geology of Region, Michigan Michigan College College of ofMining Mining and Technology, Technology, pp. pp. 41-50 and 41-50 Broderick, Broderick, T. T.M. M.(1945) (l945)"Geology "Geologyof ofthe theRopes Ropes Gold Gold Mine, Mine, Marquette MarquetteCounty, County, Michigan" Economic EconomicGeology, Geology, VoL Vol. XL, XL, pp. Michigan" pp. 115-128 115-128 Southern Complex Complex of Dickey, R. MM (1938) Dickey, (l938) "The "The Ford Ford River River Granite Granite of of the the Southern of Michigan" Journal Geology, Vol. 1-335 Michigan" Journal of of Geology, VoL 46, 46, pp. pp. 32 321335 (1961) rrprehistoric "Prehistoric Copper Drier, R. R. W. W. and DuTemple, DuTemple, 0. Drier, O. J. J. (l961) Copper Mining Mining in in the the Lake Lake Superior Region", published published privately privately Huronian) Rocks of Animikie Animikie (formerly (formerly Huronian) Fritts, C. E. Fritts, E. (1964) (l964) "Stratigraphy of Rocks of Teal Lake, Negaunee, Michigan" Transactions, Tenth Annual East East of Teal Lake, Negaunee, Michigan" Transactions, Tenth Annual Instituteon onLake Lake Superior Superior Geology Geology Institute J. E., Thaden, R. E., and Jones, Gair, Gair, J. E., Thaden, R. E., and Jones, B. B. F. F.(1961) (1961) "Folds "Folds and and Faults Faults in in the Eastern Eastern Part Partof ofthe theMarquette MarquetteIron IronRange, Range, Michigan" Michigan" Geological Geological Survey Research, Research, pp. Survey pp. 76-78 76-78 Gair, J. and Jones, B.B.F. F. (1961) "Silicification Gair, J. E., E.,Thaden, Thaden,R. R.E., E., and Jones, (1961) "Silicificationof of the the Kona Dolomite Dolomiteininthe theEastern Eastern Part Part of Kona of the the Marquette Marquette Iron Iron Range, Range, Michigan" Geological GeologicalSurvey SurveyResearch, Research, pp. Michigan" pp. 78-80 78-80 Gair, J.J. E.E.(1964) Gair, (1964) Structures Structuresin inthe theEastern EasternPart Partofofthe theMarquette MarquetteSynclinorium" SynClinorium" Transactions, Tenth Annual Institute on Lake Superior Geology Transactions, Tenth Annual Institute on Lake Superior Geology �36 36 Gair, J. (1964) uGeologic Gair, J. E. E. and andWier, Wier,K. K.L.L. (1964) "Geologicand andMagnetic Magnetic Survey Survey of of a a File, U.S.G.S. Part of Part of the the Palmer Palmer Quad., Quad., Michigan' Michigan" Open Open File, U. S. G. S. Goldich, S. S. S., S., and Goldich, and Nier. Nier, Baadsgaard, Baadsgaard,Hoffman Hoffmanand andKrueger Krueger(1961) (1961) II'The The Precambrian PrecambrianGeology Geology and andGeochronology Geochronology of of Minnesotat Minnesota" Bulletin 41, Bulletin 41, Minnesota Minnesota Geologica.l Geological Survey Survey Hydrothermal Leaching Leachingofof IIron Ores of (1937) "Hydrothermal John W. , (1937) Gruner, John Gruner, W., ron Ores of the the Modified Theory" Theory" Economic Economic Geology, A Modified Superior Type - A Lake Superior Lake Geology, Vol. XXXII, pp. 121-130 (1946) "Dickite and Chromium Silicate J, W. (1946) Gruner, J. "Dickite and Chromium Silicateininthe the Iron Iron Ores Ores of of Marquette and and Gogebic Gogebic Ranges, Ranges, Michigan' the Marquette Michigan" America.n American Mineralogist, Mineralogist, Vol. 31, 31, p. Vol. p. 195 195 Han, Tsu-Ming (1962) 'Diagenetic Han, Tsu-Ming (1962) "Diagenetic Replacement Replacement in in Ore Ore of of the the Empire EmpireMine Mine of Northern Northern Michigan, Michigan, and of and Its I ts Effect Effect on onMetallurgical MetallurgicalConcentration" Concentration" Paper presented Paper presented at at Institute Instituteon onLake LakeSuperior SuperiorGeology Geology Upper Huronian Sedimentation in Portion of Hase, D. Hase, D. H. H. (1957) (1957) "Upper Huronian Sedimentation in aa Portion of Trough, Michigan" Journal ofGeology, Geology,pp. pp.561561574 Marquette Trough, Marquette Journal of 574 from Ishpeming ((Covers Covers from! shpeming to to Champion) Harold L. Soft Iron Iron Ores Ores of Michigan" James, L. (1953) (1953) "Origin "Originof of the the Soft of Michigan" James, Harold pp. 726-'728 Vol. 48, Economic Geology, Vol. 48, pp. 726-728 "Sedimentary Facies of Iron-Formation" Harold L. James, Harold L. (1954) ( 1954) "Sedimentary Facies of I ron-Formation" 235293 Geology, Vol. Economic Economic Vol. 49, 49, pp. pp. 235-293 James, Harold PreJames, Harold L. L. (1955) (19 55) "Zones "Zonesof of Regional Regional Metarrorphism MetanV:::!t"phism in in the the Pre­ Michigan' Bulletin, Geological Society Cambrian of Northern Cambrian of Michigan" Bulletin, Geological Society of of Vol. 66, 66, pp. pp. 1455-1487 America, Vol. America, James, Harold ofPre-Keweenawan Pre-Keweenawan Rocks James, Harold L. L. (1958) (1958) "Stratigraphy "Stratigraphy of Rocks in in of Northern Michigan" Professional Paper 314-C (44 pp) parts of Northern Michigan" Professional Paper 314-C (44 pp) U. S. U. S. Geological Geological Survey Survey Isotope James, Harold L. and Clayton, James, Harold L. and Clayton, R. R. N. N. (1962) (l962) 'Oxygen "Oxygen Isotope in Metamorphosed ron Formations Formations of fractionation in fractionation Metamorphosed II ron of the the Lake Lake Superior Region and in Other IronRich Rocks' Buddington Superior Region and in Other Iron-Rich Rocks" Buddington Volume, Volume, Geological Society Society ofofAmerica, America, pp. Geological pp. 217-239 217- 239 Lamey, Carl "The Palmer Lamey, Carl A. A. (1935) (935) "The Palmer Gneiss' Gneiss" Bulletin, Bulletin, Geological Geological Society Society 46, pp. pp. 1137-1162 l1371162 of America, Vol. of Vol. 46, Lamey, Carl 'Republic Granite Granite or orBasement Basement Complex" Complex" Lamey, Carl A. A. (1937) (1937) 'IRepublic Journal of Geology, Vol. XLV, pp. 387510 Journal of Geology, VoL XLV, pp. 387-510 Leech, G. G. B., C. H. H. and and Wanless, Wanless, R. R. K. Leech, B., Lowdon, Lowdon, J. J. A., A., Stockwell, Stockwell, C. K. Paper 63l7, (1963) "Age Determinations and Geologic Studies (1963) "Age Determinations and Geologic Studies" Paper 63-17, Geological Survey Survey of of Canada Canada Geological (1931) "Secondary 'Secondary Concentration Concentration of Lake Superior Superior Iron Iron Ores" Ores" C. K. Leith, C. Leith, K. (1931) of Lake Economic, Vol. 26, VoL 26, pp. pp. 274-288 274-288 C. K., K., Jund, Jund, R. R. J. J. and and Leith, Leith,A.A,(1935) (1935) PreCambrian Rocks Leith, C. Leith, l!Pre-Cambrian Rocks of of 184 (34pp) USGS Paper the Lake Superior Region" Professional the Lake Superior Region" Profession2.l Paper 184 (34pp) USGS Oxidation to to the the Origin The Relation Mann, Virgil Mann, Virgil I. 1. (1953) (1953) t: The Relation of of Oxidation Origin of of Soft Soft Iron Iron pp. 25l281 Vol. 48, of Michigan' Economic Geology, Ores 'l Ores of Michigan Economic Geology, Vol. 48, pp. 251-281 Stephen (1942) (1942)"Iron "Iron Ranges Ranges of of the the Lake Lake Superior Superior Di.strict District"li Royce, Stephen Royce, Ore Deposits Deposits as as Related Related to to Structur2.l Structural Features Features edited Ore edited by by W. H. Newhouse, pp. 54-63 W. H. Newhouse, pp. 54- 63 2icGeoiar, Economic Geology, �37 37 Snelgrove, A. K., K., Seaman, Seaman, W. A., andAyers, Snelgrove, A. and Ayers, V. V. L. L. (1944) (1944) Minerals Investigations Baraga Strategic Minerals Investigations in in Marquette Marquette and and Baraga Counties, 1943" Progress Report Number Ten, Michigan Counties, 1943" Progress Report Number Ten, Michigan Geological Geological Survey Survey (69 (69 pp) pp) Stockwell, Stockwell, C. C. H. H.(1962) (1962)HA riA Tectonic Tectonic Map Map of of the the Canadian Canadian Shield" Shield rl Shield" Special pp. 6-15 pp. 6-15 in in "The rlThe Tectonics Tectonics of of the the Canadian Canadian Shield" Special Publication No. 4, The Publication No.4, The Royal Royal Society Society of of Canada Canada Stone, John Stone, John G. G. and and Cumberlidge, Cumberlidge, John JohnT. T.(1964) (1964)"Geology "Geology of of the the Groveland Orebody, Groveland Orebody, Iron Iron Mountain, Mountain, Michigan" Michigan" A.I. A;r. M. M. E. E. 0. and Zinn, Justin (1930) "Report on a Portion Swanson C. Swanson, O. and Zinn, Justin (1930) "Report on a Portion of of the the Marquette Range Range Covered Covered by by the the Michigan Michigan Geological Geological Survey Survey in 1929" Geological Survey Survey (Mimeographed in 1929" Michigan Michigan Geological (Mimeographed -- 15 15 pp) Swanson, C, Swanson, C. 0. O.(1933) (1933)"Geology "Geology of ofthe the Marquette MarquetteRange" Range "Guidebook Guidebook 27 27 Lake Superior Superior Region, Region, International Congress, Lake International Geological Geological Congres s, pp. pp. 10-21 10-21 Tyler, Superior Soft Ores from Tyler, S. S. A. A.(1949) (1949) "Development II Development of of Lake Lake Superior Soft Ores from MetamorphosedIron-Formation Iron-Formation'" Bulletin, Metamorphosed Bulletin, Geological Geological Society Society of America, America, Vol. of Vol. 60, 60, pp. pp. 1101-1124 1101-1124 Tyler, S. StratiTyler, S. A. A. and andTwenhofel, Twenhofel, W. W. H. H. (1952) (1952) "Sedimentation "Sedimentation and and Stratigraphy of the Huronian of Upper Michigan" American Journal graphy of the Huronian of Upper Michigan" American Journal of of Science, Vol. Science, Vol. 250, 250, pp. pp. 1-27, 1-27, 118-151 118-151 Hise, C. Lake Van VanHise, C. R. R. and and Leith, Leith, C. C. K. K. (1911) (1911) "The "The Geology Geology of of the the Lake Superior Region" Monograph Monograph52, 52, U. U. S. S. Geological Geological Survey Survey (641 (641 pp) pp) R. C. Vickers, R. C. (1956) (1956) "Geology "Geology and and Monazite Monazite Content Content of of the the Goodrich Goodrich Quartzite, Palmer Quartzite, Palmer Area, Area,Marquette MarquetteCounty, County, Michigan" Michigan" U.S. Survey, Bulletin U. S. Geological Geological Survey, Bulletin 1030-F 1030-F Zinn, Justin of the the Portion Zinn, Justin (1931) (1931) "Geology "Geology of Portion of of the the Marquette Marquette Range Range between and Lake Lake Michigamme between Humboldt Humboldt and Michigamme Covered Covered by by the the Michigan Geological Survey Survey in Michigan Geological in 1930" 1930" Michigan Michigan Geological Geological Survey (Mimeographed Survey (Mimeographed -- 18 pp) pp) , �xj 1.a. 0 C-,. Cl) CD CD C,) 0 CD () CD I..'. JQ 0 C-,. C) I-i U) P II CD '-a. C)CD C)CD CD Cl) CD0 ,. 0 CD H0 I1 PC) CD pJ. 1rJ �Figure 2 - North Jackson Mine No. I Pit, 1860 �MARQUETTE IRON RANGE, MICHIGAN THE CLEVELAND-CLIFFS IRON COMPANY — + DEER L AKE 4 + JN A C- II5 14 Il I BUSH 4 J6, 9 7 r LOG LAKE 4 JiGLASS c II 4( 120 30 I '3 8 '5 48 29 'tAKE 26 29 / %L N LDM/NE 4K LAKE' ,,1 7 ——-.7_ — \35 32 36 34 SPRUCE &NW HEARILAKEJ 4430• —-' 8);q 10 I 2 ---1h 'CE Jj7y(LAE (/ '3 '4 15 18 4731 4( '—'{20 22.- 21 .. 20 24 .. -- LEGEND 34 tAlla lU1U111Ul I 8 1 7 ° 6 2I 35 TY '-" & lUc I 9' SANDSTONE, CONGLOMERATE DIABASE KEWEENAWAN INTRSOIVES, LAVA FLOWS, SANDSTONES S RA N IT ES BASIC MET/I— ISNEOSS 4 PAINT RIVER MOSTLY INTRUSIVE FOUND IN THE SOUTHWEST SF THE MARQUETTE RANGE GROUP BA RAG A MICHIGAMME GROUP l4 23 22 3 MI DDLE '5 I 46 '30 46 20 22 2R 26 28 ..I PEN LASE HEAD II :1 35 36 y rE 33 5805 29 27 IL 89.So• 32 - CLARKSBURS PYROCLASTICS GREENWOOD MAGNETIC MEMBER GOODRICH QUARTZITE, ARSILLITE, CONGLOMERATE NEGAUNEE IHON FORMUTION MENOMINEE PRE — CAMBRIAN (OIUMS-AJIBIIY GROUP 24 UPPER ARGILLITE, SRUYWACKE RIJIKI IRON FORMATION MIDDLE ARSILLITE, URUYWUCKE LOWER ARGILLITE, SLATE, SRAYWACKE 0 tRANT 33 JACOBS VILLE CAMBRIAN LATE •- j, LAKE 32 RECENT GLACIAL DEPOSITS QUATERNARY PAL EOZ OIC I 5 34 OF THE GEOLOGIC ;: h': 3V 3' PRINCIPAL DISTRICT COLUMN MODIFIED FROM U.S. GEOLOGICAL SURVEY ,• 25 26 27 0 CHOCO LAY UNDIFFERENTIATED IN URSILLITE, SRAYWACIYE CONTAINS SGSSE LAKE SLATE AJI 81 K QUARTZITE — T4IINTGTHICK WEWE GRAY SLATE — LOCALLY QUARTZTES , CONSLSMERATE KONG DOLOMITE — M'NOR QUARYZIYESILT!YE MESNARD IR SNFORMAT ISN QSARTZITE CONGLOMERATE, GRAYWACKE, ARKOSE FELSITE PORPHYRY EARLY WESTERN PSRTIONI SI AMO GROUP MONA MUD 20 TONALITE, GRANODIORITE SCHISTS, METASEDIMENTS, SNEISOES GREENSTONE, MASSIVE — ELLIPSOIDAL FELSITE, METABASALT 8 6 7\REI 48 26 E 1421 —-- 23 22 LL 2/ a :)uN -:S jACR DAM 26 25 26 27 '3 24 23 21 PETrICOATK 32 _r CKY E ROUND ALAKE 'I6 8 5 18 5 FIGURE 4 25 41 S7J I \ \\ AROUETr H I I • 5 l5 29 �MAR QUE TIE IRON RANGE MICHIGAN GENERAL IZED CROSS SECTION Nrn-S ONE MILE EAST OF WEST LINE OF R.26W FIGURE 6 LOOKING WEST S N TRACY MINE NEGAUNEE - MAAS ilpgu- /964- �FIGURE 7 GRAPH SHOWING RELATIVE THICKNESSES OF ANIMIKIE SEDIMENTS ON THE MARQUETTE RANGE LOOKING NORTH HUMBOLDT M I C HI GAM ME ENCHANTMENT LAKE ISHPEMING 3 m SW of Marquette EROSION 7,, / / / // U /// / / / / / / / // / 9 0 0 (9 (1) /7 4 — — LLJ— zl / / / — = (9 2 i: —--- 7 — —0—— — — 7 —- F- — — / / / — 7 7 —_ GO° 7 0. 0 0 (9 U U z * WEWE / 7 77 7 V / V 0 / / / (0 / c, I I / / / 4) / / I, I/ / 1/ z— / // 4 0 0 / 7 (9, / V V V 0 ,0 -J ,,,0 7- 'N I0 — KONA I —— — — +- ___(I)_ w -7 84S4L, — SLAMO — AJI8IK -I--I 400 400 FEET 800 200 Vertical Scale SEcT,0 UNDI FFERENTLATED Dl STRIBUTION Horizontal 8000 Scale - — 000 8000 FEET 6000 2 ' 24000 �t C') p with magnetite - che rt carbonate - silicate Chert-silicate containino carbonate and rnagnetie Magnetite lan-dna alternating Magnetite lamina alternating with magnetite-chertcarbonate -silicate Silicate -chert containing some carbonate Magnetite lamina alternating with silicate-carbonate Silicate -carbonate granules, various shades; chert, white D. Magnesium iron carbonate t '1 Thin section ZGUX Athens Mine A. Cherty Carbonate I-Fm. 0 n 0 0rt- Polished slab of Inn-Formation Natural scale S g roundmas s E. and F. Pol.Sec. lCUX B. Mag. Chloritic Ciastic I-Fm. C. Mag. Urunetitic Cherty I-Fm. Thin section i O X Empire Mine Thin section IGUX Republic Mine Coarse magnetite and quartz Grunetite, gray; chert, dusty granules with chioritic white: magnetite. black 1 0 I: CD �oi U) H I 0 C whitish gray; chert and quartz, dark gray Martite, white; magnetite, H. Same - Pol. Sec. 100X G. Martitic Cherty Clastic I-Fm. Natural size Cherty Goethitic I-Fm. Natural size Martite, white; goethite, gray; chert, dark gray; and pits, black J. Same - Pal. Sec. bOX I. gray; chert, dark gray Cherty I-Fm. Pal. Sec. 100X Hematite, white; magnetite, L. Magnetitic Specularitic K. Specularitic Cherty I-Fm. Pal. Sec. 100X - Hematite, white; chert, black U) oQ 0 0 0 (L çi �';! AAf fl grey. As N. 500x Hematite, white; and gangue and pores, dark A ;, soft hematite. Hematite white. Pci. sac. lOOx. i. Nather : : t: . e * .a: +1* ? •• Ø ''S — — —— — Pol. sec. bOx P. Mather hard rnartitic ore. K. Cliffs-Shaft Magnetite. Magnetite, greyih white; Martite, white; pore, black, hematite, white; gangue Pol. sec. lOOx. dark grey, and pit black. Fob. sec. lOOx I T. As S. Fob. sec. lOOx Hematite, greyish white; martite, white, gangue, dark grey. 0. Mather soft martitic ore. Q. Cliffs—Shaft hard hematite S. Cliffs—Shaft ore conglomerate. Hematite, white; and Martite, white, chert, Natural size. Magnetite, greyish white. dark Fob. sec. lOOx Hematite, greyish white. • V V I 0 0 CD p �GEOLOGY OF NEGAUNEE IRON FORMATION EMPIRE MINE AREA AND CASCADE DISTRICT 1000 000 2000 l0O0 GENERALIZED CROSS SECTION MINE AREA, SEC. 19, 47-26 E-W X-SEC. A-A' LOOKING NORTH EMPIRE 400 4?0 800 +1600 PM 0 0.01-1. 9 + 200 + 800 --(i_— 2 21122 201121 22 23 LEGEND I! GOODRICH QUARTZITE UNOX. IRON FORMATION OX. IRON DIORITE LOWER MIDDLE ANIMIKIAN E1 METASEDIMENTS OX. IRON FORMATION ARGILLITE ————-————-——-—-—--—————___._____.L0_____________ 30 EMPIRE INTRUSIVE P7 ROCLA ST IC CLASTIC SIAMO—AJIBIK FORMATION 28 CONC. PLANT 32 LATT MiNE 27 �OF GEOLOGY THE REPUBLIC MINE AREA PA ....\ 'A \\. f; r . ::..•1I. 55 N PIT GENERALIZED CROSS SECTION LdOKING A—A' N— E -dole'4t0 000 S 6 Ef FL AN AT tN Metasnd imentn I4ichipamnme Formation Nicacmoan, parmetiferoas aod amphibalitic nchints tdoadrick Formafian Qnartzites, metapraymacken and mica schists Negaannn Iron—Format Ion Coeplameratic iron tormatiar Spmcalar hematite — mapnotite cherty iron—formation Silicate iron—formation AJitik Formation lgnmaan Ojartzites, metapraymackas. feldnpathic pmmisnnn and mica nchintn ('I) *.ImtadioniteS & knph,bolites ftntly nralitic nub fepabi ic Camplen Pnrphynitin and epnipraenlar oraniton mith ainphitol iten. At leant in part represents pranitizod sediments Faa It Contact (appronimate) Strike and dip of tnddinp S Strike and dip of foliation tnrike and dip of jointing tntcrop area OPhIL, 19t3 - 4 3 — ���������������������THE CLEVELAND-CLIFFS IRON COMPANY O)MARQUETTE IRON RANGE, MICHIGAN GEOLOGIC COLUMN OF THE PRINCIPAL DISTRICT MODIFIED FROM U.S. GEOLOGICAL SURVEY RECENT GLACIAL DEPOSITS SANDSTONE, CONGLOMERATE S NA N IT ES BASIC META— IGNEOUS MOSTLY INTRUSIVE MARQUETTE RANGE FOUND IN THE SOUTHWEST OF THE UPPER ARUILLITE, URAYWUCKE BIJIKI IRON FORMATION MIDDLE ARUILLITE, GRAYWACKE CLURKSBURG PYROCLASTICU GREENWOOD MAGNETIC MEMBER LOWER ARSILLITE, SLATE, URAYWACKE QUARTZITE, ARUILLITE, CONGLOMERATE IRON FORMATION ISIAMO—AJIBIK UNDIFFERENTIATED ARGILLITE, GRAYWACKE SLATE — CONTAIN SAUUSELAK E IN WESTERN IR ONFORMAT ION QUARTZITE — THINTOTHICIIB EBBED GRAY SLATE — I. OCALLY QUARTZflEG DOLOMITE — ONOR 000RTZITE , CONGLOMEBAT SIL1IlE QUARTZ lIE CONGLOMERATE, GRAYWACKE, ARKOSE FELSITE PORPHYRY TONALITE, URANODIORITE GCHIDTU, METASEDIMENTS, GNEISSES GREENUTONE, MASSIVE — ELLIPSOIDAL FELSITE, METABASALT FIGURE 4 � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1964 Description An account of the resource Institute on Lake Superior Geology. Ishpeming, Michigan. May 6-9, 1964. Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1964 Contributor An entity responsible for making contributions to the resource J.E. Case Jacob E. Gair Crawford E. Fritts Stephen C. Nordeng A.K. Snelgrove J.T. Mengel W.W. Moorhouse Paul A. Lindberg Carl E. Dutton T.H. Nilsen John W. Trammell Chester O. Ensign Jr. M.W. Bartley J.M. Neilson Leonard W. Weis J. Allan Cain Kiril Spiroff R.E. Lubker Virginia L. Doane E.G. Pye V.G. Milne A.V. Heyl J.W. Hosterman W.E. Hall M.R. Brock John C. Green A.S. MacLaren S. Duffell Robert Patenaude Gerald Van Voorhis Lloyal Bacon Charles E. Karman William J. Hinze A.W. Schillinger G. Haure P.M. Hurley G.G. Stuffel Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English https://digitalcollections.lakeheadu.ca/files/original/37cabe0e7ea7bfdd9ba9dcbc494adb36.pdf cd719f14ad23652fa7736dc1061d666b PDF Text Text Eleventh Annual Institute on Lake Superior Geology May 6-8, 1965 University of Minnesota St. Paul Minnesota �11thAnnual AnnualInstitute Institute on lith Superior Geology Geology Lake Superior Sponsored by: 3ponsored Minnesota Minnesota Geological Survey of Minnesota Minnesota University of and The Twin The Twin City Geologists Wicons,i GIoccaj ad Na1ur Hiry 9igj 3811 M;rior pci,,t flc. Madj5Qfl, WI 63; i �r7j ch§Technical Technical tlJI Sessions n I I I., > (TZR .----- a '-- ST PAUL CAMPUS CAMPUS 1 J �COMMITTEES Local Committee Local Hogberg General Chairmen - P. K. K. Sims and R. R. K. Hogberg Program Program Arrangements Social P. P. K. K. Sims Sims Judy Holmes Keith Knobloch I(nobloch CnarLes Matsch Cnarles Jane Titcomb Jane Titcomb Sarah Tufford Sarah D. y.;. Lindgren Lindgren D. W. George Austin George R. R. K. K. Hogberg Hogberg Field Field Trip t. K. R. K. Hogberg Hogberg D. D. H. H. Yardley Yardley Institute Secretary Secretary Institute D. H. Hase, D. Hase, State State University Universityof of Iowa Iowa Institute Eoard Board of Directors Institute M. M. W. W. Bartley, M. M. W. W. J3artley Bartley & & Associates, Associates, Port Port Arthur, Ontario A. A. T. T. Broderick, Broderick,Inland InlandSteel SteelCompany, Company, Istipeming, Ishpeming, Michigan Michigan D. H. Hase, State University of Iowa, Iowa City, Iowa D. H. Hase, State University of Iowa, Iowa Iowa H. Lepp, Lepp, Macalester MacaLester College, College, St. Paul, Paul, Minnesota Minnesota H. A. A. K. K. Sneigrove, Snelgrove, Michigan Michigan Technological Technological University, University, Houghton, Houghton, Michigan �11th Annual Institute on 11th Annual Institute on Lake SuperiorGeo1o~ Geolo_ Lake Superior May May 66 -- 8, 8~ 1965 PRO GRAM PROGRAM Thursd, Thursday?May May 66 8:00 - 9:20 a.m. a.m, Registration and coffee coffee hour9 hour 9 2nd floor floor of of Student Student Center, center, St. Paul Paul Campus st. Campus Technical sessions,9 2nd Technical sessions 2nd floor, f1oor~ Green Hall 8:45 -- 9:00 9:00 Business Meeting...........D. Hase, Secretary, Meeting ••••••••••• D. H. H. Hase~ Secretary, conducting Session II Co-chairmen: and Ralph John W. W. Gruner and Marsden 9:00 Progressive contact metamorphism of the Biwabik Iron-formation on on the 9:20 9:40 10:00 10:45 11:05 11:25 12:15 Nesabi ,........Bevan M. French Mesabi range, range, Minnesota....................... Minnesota •••••••••••••••••••••••••••••••• Bevan M. The distribution of manganese in the Biwabik Iron-formation, Minnesota.••••••••••• Minnesota Henry Lepp . . . . . . . . . • ~ ••••••••• ..•...... .. .e ••.• •.•.• •.•.• •. c •. •• •.•.•.•.•.•.•.• .• •. .~ .••• •• ••.• •.Henry Some aspects of of iron-formations in Australia and South Africa.. . . . •. . . . . ........ . . , . . , . . . . . . . . •. . . . . . . . . . . . . .Gene Africa •••••••••••••••••••••••••••••••••••••••••••••••• • Gene L. L. LaBerge Coffee break Structure and and lithology of of the metamorphosed Biwabik Biwabik Iron-formation, Iron-formation, Dunka River area, area, Eastern Mesabi district, district, Minnesota••• Minnesota. . Bil1 Bonnichsen Structural control control of of the Mount Mount Wright-Mount Wright-Mount Reed Reed iron iron deposits, Structural .Bill J. Clarke Quebec •••••••.••••••.••••••••••••••••••••••• • • • • • •.•. •• Peter J. Quebec...... . ........ .... . . . . . . . . . . . . . . . . . .o ........ . •.Peter Petrology of the silicate iron-formation in the Republic mine area, area, Marquette County, County, Michigan............Tsu—Ming Michigan•••••••••••• Tsu-Ming Ban Han and and James James W. W. Villar Villar Luncheon, Student Center, Luncheon, Center~ 2nd floor, floor, North Star star Ballroom Ballroom Session II II Co—chairmen: Co-chairmen: 1:30 1:55 2:15 2:35 2:35 2:50 3:35 3:35 3:55 3:55 4:15 4:15 George M. M. Schwartz and James Neilson Tectonics of the Keweenawan basin, basin~ western Lake Superior Superior S. White region. . . . . . . . . . . . . . . . . . . .. .o .• ,• • region ••••••••••••••••••••• • Walter S. . •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. •. .WaJ.ter of western western Lake Lake Superior...........Richard Superior•••••••••• Richard J. J. Wold An aeromagnetic survey of The Sauble geophysical geophysical anomaly, anomaly, Lake Lake County, County, Michigan.....................G..HowardJ. Michigan••••••• o • • • • • • • • • • • • • • • ~ • • Howard J. Meyer Meyer and and WilliamJ. William J. Hinze Hinze Contributions of rock rock physics physics to to geology•••••••••••••••Robert geology..,...........Robert J. J. Willard Coffee break Geological analysis and remedial action action in in an open pit rock slide. slide ••••••••••••••••••••••••••••••••••••••••••••••• D. H. H. Yardley rock . . .. . . . . . . . . . . . . . . . . . . . ,. . . . . . . . . . . . . . . . . . . . . .D. Measurement of in-situ stresses in in aa St. st. Cloud quarry-quarry--aa Measurement progress progress report. report •••••••••••••••••••••••••••••••••••••• . ......... .... •. .... .. . . ..... ..... .. . Charles Char1es Fairhurst Fairhurst An example of statistical analysis and possible interpretation and interpretation of of Hill, Skanee quadrangle, quadrangle, Upper structural data from Arvon Hill, Peninsula, Michigan ••••••••••••••••••••••••••••••••••••• J. D. Juilland Peninsula, Michigan. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . . . . J • 1 �Thursday9 May Thursday, May 66 (continued) ~continued) Annual Annual Banquet Twins Motor Motor Motel Motel 1975 University Avenue (University at at Prior) Prior) 6:00 6:00 p.m. p.m. 7:00 Social Hour Social Dinner Address: Professor Campbell Campbell Craddock Craddock will will speak speak on on 'Geologic QfGeologic Professor structure of West West Antarctica,' Antarctica, 'I a summation summation of six six structure austral austral seasons seasons of field work work illustrated illustratedwith withmany many of field colored pictures. pictures. fine colored Friday, May May 77 Friday, Co—chairmen: Co-chairmen: 9:00 9:00 9:20 9:40 Session III III Carl E. E. Dutton Dutton and and H. H. L. L. James Stratigraphy, structure, structure~ and and granitic granitic rocks rocks in in the the Marenisco—Watersmeet Marenisco-Watersmeet, Stratigraphy, E0 Fritts'~ Fritts area, area, Michigan. Michigan•••••••••••••••••••••••••••••••••••••• .. .. .. .. ... .. .. ... .., .. .. .. .. . . •.. . Crawford E. Ages of mafic dikes near Granite Falls, near Granite Gilbert N. N. Hanson Minnesota •••••••••••••••••••••••• Glen R. Hixmnelberg, Himmelberg~ Gilbert structure and stratigraphy stratigraphy of of the the Knife Knife Lake Group Group east east of of Ely, Ely, Structure and a •a•a•a. Minnesota...... Minne sota •••••••••• ••••• ••• • •,John John C. C. Green . . . ~. •••••••••••••••.•••• . . . . . .. . . . .... .. . . . . e ••e a. ••a.•. a•a. Coffee break Spiroff,. Keweenaw fault, Houghtori Houghton County, Michigan •••••••••••••••••• Kiril Spiroff~ Keweenaw fault, County, Michigan.... ... .. s... •• .lCii'il The sedimentology sedimentology of the the Precambrian Precambrian Rove Rove Formation Formation in in , B. Morey Morey --northeastern northeastern Minnesota.., Minnesota••••••••••••••••••••••••••••••••••••• G. B. ~ .. . . . .. . .. . .. .. .. ... .. ... . ... . .G. Petrology Petrology of the the Amberg Precambrian Precambrian crystalline crystalline complex, complex, .Dennis northeastern northeastern Wisconsin...,.... Wisconsin••••••••••••••••••••••••••••••• Dennis p. P. Rebello ....... Sedimentation of Middle Precambrian quartzites quartzites in in Sedimentation of R;chard W. OJ'akangas~ W. Ojakangas Finland. F;nland ..•,•.•.•.•.•.•.•.•.•$• •. ., •. •. •. •. •. •.•..• •. •. .0 .• •. •. ••,• •• •, •. •, •..• •. •. •. ." ..Richard • •. •• 1'\ Luncheon, Center, 2nd floor, Luncheon, Student Center, floor, North Star Ballroom Minnesota........,.,........,..GlenR. . 10:00 10:40 11:00 11:00 11:20 11:40 •.•,.,...• .... ..I. 12:15 Co-chairmen: 1:30 1:50 Session IV G. A. A. Thiel Thiel and and Don Don Lindgren Lindgren G. A study on the the hydrology hydrology of of potholes potholesin inMinnesota••••• Minnesota.....George Schwartz A study on George M.M.Schwartz -~' Geology of the the Fillmore County district iron ores, L. Bleifuss southeastern southeastern Minnesota..,. Minnesota•••••••••••••••••••••••••••••••••• R, L. ...... ... . .... .......... . ,. ,R, Organic geochemistry geochemistry of of Rossburg Rossburg peat peat bog, bog, Aitkin Aitkin County, County, F. M. M. Swain, Swain, Mykola Mykola Nalinowsky, Malinowsky, and and David David Nelson Minnesota•••••••••••••• Minnesota.............F. Preliminary Prelimina:ry results results of of geochemicaT geochemical prospecting prospecting north north of of the the Marqu~tte ••••••••••••••••••••••• Kenneth Segerstrom Marquette iron iron range, range, Michigan Michigan......................Kenneth Coffee Coffee break break Protoclastic borders borders of of the the felsite felsite near near Bergland, Bergland, Protoc1as;ic Michigan..........0.........Joseph Michizan •••••••••••••••••••••• Joseph P. P. Dobell Dobell and and Robert W. W. Leonardson Some aspects aspects of of the the pegmatites pegmatites in in the the Feich Felch district, district, Dickinson Dickinson Some •••••••••••••••••••••••••••••••••••• Geoffrey W. W. Mathews Mathews County, Michigan County, Miehigan...................................Geoffrey . 2:10 2:10 2:30 2::30 2:50 3: 20 3: 3:40 3:40 2 2 �Friday9 May Friday? May 77 (continued) (continued) 7:30 —- 9:Lk5 9:45 p.m. U. S. S. Bureau of Mines, Mines, Research Research Center, Center, Fort Tour of U. Bus will leave at 7:30 Snelling. 7:30 p.m. p.m. from Student Student Snelling. Center, st. St. Paul Campus with an intermediate stop center, at Twins Motor Motel and and will will return return to to the the same same at locations. Saturday, May 8 Saturday? 8:00 a.rn. to 8:00 a.m. to 6:00 6:00 p.m. p.m. Field trip trip to to St. st. Cloud Cloud district. district. Buses will depart Field from and and return return to to the the Student Student Center, Center, St. St. Paul Paul campus. campus. from Field trip willinclude include tour tourofofthe theCold ColdSpring Spring Granite Granite Field trip will CompanyO s finishing visits Companys finishingplant plantandand visitstotothree three"granite: 'granite' quarries. Participants will will be be provided provided with with aa guideguidehats are hard book and. and lunch. clothes and and are advised. advised. lunch. Field clothes Authors and and Technical Technical Session Session Chairmen Chairmen BLEIFUSS, R. L...........Mines BLEIFUSS, R. L••••••••••• Mines Experiment Experiment Station, Station, University University of of Minnesota, Minnesota, Minneapolis Minneapolis BONNICHSEN, BILL....0...Department BONNICHSEN, BILL ••••• o • • • Department of of Geology Geology and and Geophysics, Geophysics, University of Minnesota, Minne sota, Minneapolis Minneapolis ~X ,. CLARKE, PETER PETER JJ.........Department CLARKE, •••••••••• Department of of Natural Natural Resources, Resources, Province Province of of Quebec, Quebec, Quebec, Canada Quebec, Geophysics, University CRADDOCK, CAMPBELL •••••••.Department Department of Geology and and Geophysics, University of of CAMPBELL..... Minnesota, Minneapolis Minneapolis DOBELL, JOSEPH DOBELL, JOSEPH P....... P•••••••••.Department Department of of Geology Geology and and Geological Geological Engineering, Engineering, Michigan Technological Technological University, University, Houghton, Houghton, Michigan Michigan Michigan " DUTTON,CARL CARLE...........U. E••••••••••• U. S. S. Geological Geological Survey, Survey, Madison, Madison, Wisconsin Wisconsin ADUTTON, FAIRHURST, CHARLES•••••••.School School of of Mineral Mineral and and Metallurgical Engineering, FAIRHURST, CHARLES..... University of Minnesota, Minnesota, Minneapolis Minneapolis FRENCH, BEVAN M •••••••••• Theoretical Division, Goddard Space Space Flight Flight Center, Center, M..........Theoretical Greenbelt, Maryland Greenbelt, Maryland )(FRITTS, CRAWFORD E••.•••• E......U. XFRITTS, CRAWFORD U. S. S. Geological Geological Survey, Survey, Denver, Denver, Colorado Colorado GREEN, GREEN, JOHN C............Department C•••••••• o • • • Department of of Geology, Geology, University University of of Minnesota, Minnesota, Duluth Duluth GRUNER, JOHN JOHN W.o W..........Professor and GRUNER, ••••••••• Professor Emeritus, Emeritus, Department Department of Geology and University of of Minnesota, Minnesota, Minneapolis Minneapolis Geophysics, Geophysics, University Company, Ishpeming, HAN, TSU-MING Cleveland-Cliffs Iron Comp2ny, Ishpeming, Michigan TSU-MING,•••••••••••• . . . . .,. . . Cleveland—Cliffs HAN, .. Institut HANSON, GILBERT GILBERTN.l'l •••••••• Institut fur Kristallographie und Petrographie, Petrographie, HANSON, ... Sonneggstrasse, Zurich, Switzerland Sonneggstrasse, Zurich, S\\I:Ltzerland / Geology, University University of j('HASE, D. H••••• , •••• o • • • • Department of Geology, of Iowa, Iowa, Iowa Iowa City, City, XHASE, D. k~ Iowa HIMMELBERG, HThIMELBERG, ..Departm.nt GLE:J R.. R••••••• Departm,mt of of Gtology Gt~ology and and Geophysics, Geophysics, University of GIE Mirmesota, Minneapolis Minl!~apol:'Ls Minnesota, HINZE, XNZE, ~ 'V': , (, '. ,;lJ \ !~'~i\.. Geology, Michigan University, 7J '" WILLIAM ~f.[LLI.AM J.........Department J ••••••••• Department of of Geology, Michigan StateState University, ~t ~i~\ j/l>';'>:: East Lansing, Michigan J3 ,f �P .,~N·".I' ,'vV' () AHOGBERG, .J( HOGBERG~ R.R.K............Minnesota K••••••••••••Minnesota Geological Geological Survey, Survey, University University of of Minnesota, Minnesota, JAMES, JAMES~ Minneapolis H. L•••••••••••••• G0010gical Survey, Survey, Minneipolis MiQDo~polis L............U.D.S.S.Goological JUflL.A1D, J. JUILLAND, J. D..........Michigan D••••••••.•• Michigan Technological Technological University, University, Houghton, Houghton, Michigan Michigan ,.;zLaBERGE, LaBERGE, GENE L•••••••••• National Research Council Council of of Canada, Canada, Geological Geological L.........NationaJ. Survey of Canada, Canada, ottawa, Ottawa, Ontario LEDNP1RDSON, ROBERT W.. LEONARDSON, ROBERT W••••• Department of of Geology Geology and and Geological Geological Engineering, Engineering, . .Department Michigan Technological Technological University9 University, Houghton, Houghton, Michigan Michigan Michigan LEPP, HENRy•••••••••••••• HENRY.............Department Paul LEPP, Department of of Geology, Geology, Macalester College, College, St. st. Paul LINIJGREN, DONALD DONPLD W W.......Lindgren & Lehmann, Lehmann, Inc., Inc., Wayzata, Wayzata, Minnesota LINDGREN, ••••••• Lindgren & MALINOWSKY, MYKOLA••••••• Department of of Geology Geology and and Geophysics, University University of of MALINOWSKY, MYKOLA.......Department Minnesota, Minnesota, Minneapolis MARSDEN, RALPH W ••••••••• U.S.S.Steel Steel Corporation, iJuluth Duluth W...,....U. Corporation, MATHEWS, GEOFFREY W Reserve University, University, •••••• Department of Geology, Western Reserve W......Department Geology, Western Cleveland, Ohio Ohio of Geology, Geology, Michigan Michigan State University, MEYER, HOWARD HOWARD J...........Department J •••••••••• Department of University, East Lansing, Lansing, Michigan MOREY, G. DepartmentofofGeology Geologyand and Geophysics, Geophysics, University University of of MOREY, G. B•••••••••••••• B............Department Minnesota, Minneapolis Minnesota, NEILSON, JAMES. JAMES•••••••••••Michigan Technological University, University, Houghton, Houghton, Michigan Michigan ... ... . . . .Michigan Technological NELSON, DAVID •••••••••••• Department of of Geology Geology and and Geophysics, Geophysics, University University of NELSON, DAVID...........Department Minnesota, Minneapolis OJAKANGAS, OJAKANGAS, RICHARD RICHARD W.....Department W••••• Department of of Geology, Geology, University University of of Minnesota, Minnesota, Duluth REBELLO, DENNIS REBELLO, DENNIS P.......Department P•••••••• Department of of Geology, Geology, Western Western Reserve Reserve University, University, Cleveland, Ohio Cleveland, SCHWARTZ, GEORGE M M......Professor and SCHWARTZ, GEORGE ••••••• Professor Emeritus, Emeritus, Department Department of Geology and Geophysics, University of of Minnesota, Minnesota, Minneapolis Minneapolis Geophysics, University SEGERSTROM, KENNETH......U. SEGERSTROM, KENNETH •••••• U. S. S. Geological Survey, Survey, Denver, Colorado Colorado P. K•••••••••••••••Minnesota K..,..0.......Minnesota Geological Geological Survey, Survey, University University of of Minnesota, Minnesota, J i~ SIMS, P. / Minneapolis SPIROFF, KfltIL...........Department KIRIL ••••••••••• Department of Geology and and Geological Geological Engineering, Engineering, SPIROFF, Michigan University, Houghton, Houghton, Michigan Michigan Michigan Technological Technological University, SWAIN, SWAIN, F. F. M•••••••••••••• Department of of Geology Geology and and Geophysics, Geophysics, University University of of Minnesota, Minnesota, Minneapolis Minneapolis THIEL, G. A•••••••••••••• A.............Professor THIEL, G. Professor Emeritus, Emeritus, Department Department of of Geology and Geophysics, University of of Minnesota, rfLnnesota, Minneapolis Minneapolis Geophysics, University VILLAR, JAMES W W.........Cleveland—Cliffs VILLAR, Jfu~ES •••••••••• Cleveland-Cliffs Iron Iron Company, Company, Ishpeming, Ishpeming, Michigan Michigan WHITE, WALTER WALTER S.........U. S•••••••••• U. S. S. Geological Geological Survey, Survey, Beltaville, Beltsville, Maryland WHITE, WILLARD, ... .U. S. Bureau Bureau of Mines, Mines, Minneapolis Minneapolis 'WILLARD, ROBERT ROBERT J.... J •••••••• U. S. 4 L. �'/WOLD, RICHARD J J........,.Department WOLDt RICHARD •••••••••• Department of of Geology, Geology, The The University University of of Wisconsin, Wisconsin, Madison, Wisconsin Madison, YARDLEY, D, H.....,......School YARDLEY, D. H•••••••••••• School of Mineral and and Metallurgical Engineering, Engineering 9 University of University of Minnesota, Minnesota, Minneapolis 55 �GEOLOGYOF OF THE THE FILLMORE DISTRICT GEOLOGY FILLMORE COUNTY COUNTY DISTRICT IRON ORES,SOUTHEASTERN SOUTHEASTERN MINNESOTA MINNESOTA IRON ORES, R. L. L. Bleifuss Bleifuss R. Station Mines Experiment Station */ University of Minnesota, Minnesota, Minneapolis— MinneapolisIron ores have been known to exist in southeastern southeastern Minnesota Minnesota since the the earliest earliest geological reconnaissance of the area by the since 9 Owen's Owen s survey survey in in 1852. The development of the the Fillmore County district was stimulated stimulated by by the the demands demands for for iron iron ores ores during during World World War II, II, and initial ore shipments shipments were made in in 1943. 1943. Cumulative tons, iron-ore million tons, iron—ore production production through through 1964 1964 has has been been about about 6t 6 million Reserves and current current production production is is about about -t million tons per per year. year. Reserves and carried on on the the tax tax rolls rolls in in 1964 1964 are are in in excess excess of of 2* million million tons. tons. 2t The iron ores lie on Paleozoic limestones ranging ranging in in age age from from the Middle Ordovician to to Middle Devonian. Devonian. The commercial ore bodies are restricted restricted to to two two dolomitic limestone limestone units: units: the the Middle Middle Ordovician Ordovician The Galena Formation, Formation, and and the Middle Devonian Devonian Cedar Cedar Valley Valley Formation. Formation. The iron ores, ores, and the widespread iron-rich weathering residuum residuum which which is is developed on nearly all of the formations formations in the the area, area, has has been been Member, of the Cretaceous Windrow ~Tlndrow assigned to the lower, lower, Iron Hill Member, Formation. Formation. The clays, sands, sands, and gravels gravels overlying overlying The unconsolidated unconsolidated clays, the the ores are assigned to the upper, upper, or or 0Ostrander same strander Member Member of of the the same formation. Previous investigators have postulated that the the ores ores in in the the district originated by intensive chemical chemical weathering, which which resulted resulted in the widespread replacement of certain certain favorable favorable dolomitic dolomitic limelimepaper on the stone by iron. iron. In the most recent paper on the area, area, stone bedrock units by In the postulated Sloan (1964) (1964) agrees agrees with the the Cretaceous Cretaceous age of the iron ores postulated by previous workers, workers, and further emphasizes the the importance importance of of humid, humid, temperate, to to sub..tropical sub-tropical climatic that prevailed prevailed in in the the temperate, climatic conditions that area during the time of the transgression of the Cretaceous seas seas over Minnesota. The present study has produced evidence that the the ores ores are are siderite-rich beds that originated originated during during the the related to primary siderjte-rjch transgression of of the the Devonian Devonian seas. seas. The uniform thickness, thickness, chemical chemical transgression composition, and physical characteristics of of the the ore are preclude preclude their their composition, formation by by the the surficial surficial weathering of of aa normal normal dolomitic dolomitic limestone limestone formation without an an intermediate intermediate concentration concentration step. step. The author believes that the the physical-chemical phy"sical-chemical conditions required required to precipitate precipitate relatively pure pure siderite siderite in in an an otherwise otherwise normal normal carbonate carbonate environment environment relatively during the the Devonian. Devonian. This would require a euxinic were present during environment in an estuary or bay with limited mixing of of normal normal marine marine waters. The by streams streams draining draining a The iron iron was wastrffilsported transported in in solution by low-lying coastal plain under arid arid or or semi-arid semi-arid climatic climatic conditions. conditions. ~/Work done on of the theMinnesota Minnesota Geological Geological Survey Survey on behalf of — Work done 66 �The ultimate ultimate source of the drainage The source of iron iron was was the the normal normal sediments sediments of drainage basin; no basin; no specific iron-rich iron-rich source source beds beds are are required. required. The ores are not necessarily dependent upon unique Cretaceous climatic conditions, conditions 9 and the advisability of placing them within the Formation is is dubious. dubious. the Windrow Formation 77 �*/ STRUCTURE AND AND LITHOLOGY LITHOLOGI OF STRUCTURE OFTHE THEMETJ\MORPHOSED METAMORPHOSED BIWABIK BIWABIK IRON— IRONFORMATION, FORMATION, DUNKA DUNKA RIVER AREA, AREA, EASTERN MESABI MESABI DISTRICT, DISTRICT,MINNESOTA MINNESOTA- Bill Bonnichsen Bill Bonnichsen Department of Geology Geology and and Geophysics Department University of of Minnesota, Minnesota, Minneapolis Minneapolis A three-mile—long three-mile-long belt of of metamorphosed metamorphosed Biwabik Biwabik Iron-formation Iron-formationA in the Dunka River area, Babbitt, Minnesota, Minnesota, at area, near Babbitt, at the eastern eastern end of the Mesabi Range, is being developed developed by Erie Erie Mining Company Company as as aa Range, is taconite property. property. age, rests with profound The The Biwabik Biwabik Iron-formation, Iron-formation, Animikian Animikian in age, profound on granitic granitic rocks rocks of of the the Giants Giants Range Range batholith batholith and and is unconformity on unconformity overlain Formation. The Pokegama Pokegama Quartzite, Quartzite, overlairi conformably conformably by by the the Virginia Virginia Formation. which lies immediately immediately below the the Biwabik Biwabik Iron-formation Iron-formation in in other other parts parts these of the Mesabi range, virtually absent absent at at Dunka Dunka River. River. All of these range, is virtually older rocks have been intruded and thermally metamorphosed by the Keweenawan Duluth Duluth Gabbro Gabbro Complex. Complex. The iron—formation iron-formation and other other PreKeweenawan cambrian rocks are covered locally by as much as 100 feet of as much as 100 feet of glacial is drift. iron—formation ranges in thickness from At Dunka Dunka River, River, the iron-formation from 175 to 300 feet, to feet, and varies as as much as 100 feet in in aa short short distance distance much as 100 feet horizontally horizontally as aa result resultofofboth bothdepositionaJ. depositionaland and structurally— structurallyinduced thinning and induced and thickening. The Lower Lower Slaty, thickening. The LowerCherty, Cherty, Lower Slaty, Upper Cherty, and Upper Cherty, and Upper Upper Slaty Slaty Members Members of of the the Biwabik Biwabik Iron-formation Iron-formation are recognizable recognizable at at Dunka and, except except for for aa markedly markedly thinned thinned are Dunka River River and, Lower Lower Cherty Cherty Member, Member, the the formation formation is is similar similar in in thickness thickness and and stra— stratigraphy to to other other localities in in the the Eastern Eastern Mesabi district. district. AA persistent persistent 55- to 15-foot diabase sill, sill, believed to to be be part part of of the the Duluth Gabbro Complex, Complex, occurs occurs throughout throughout the the property property at at the the same same stratigraphic position stratigraphic position in in the the Upper Upper Slaty Slaty Member. Member. The minerals minerals of of the the Biwabik Biwabik Iron-formation—-quartz, Iron-formation--quartz,magfletite, magnetite, The fayalite, ferrohypersthene, ferrohypersthene,hedenbergite, hedenbergite,hornblende, hornblende, cummingtonite, fayalite, curniiiingtonite, and lesser amounts of diopside, diopside, actinolite, actinolite, andradite, andradite, calcite, calcite, and and pyrrhotite--are characteristic of of a high temperature metamrophic metamrophic environment. The mineralogy and paragenesis are similar similar to to that that at at environment. the the Reserve Reserve Mining Company Company (Gundersen (Gundersen and and the Peter Mitchell mine of the 1962). Quartz is the most abundant mineral in in the the iron— ironSchwartz, 1962). Quartz is formation, formation, and grains grains developed in relatively pure layers are are as as much as as 55 to 10 mm. in diameter. diameter. Magnetite, Magnetite, the the second second most most abundant abundant mm. in mineral, mineral, has haR been coarsened by the the metamorphism; its its grain-size grain-size varies varies considerably from from layer to in general, general, increases increases northward northward considerably to layer but, but, in through the property. property. The taconite shows shows reI.iograde reh'ograde metamorphism metamorphism with hydrous iron—silioat,e forn-thg at the expense iron-si1icateLr1itxer] miner-a] ~s fOl"lJli ng at expense of ofanhydrous anhydrous varieties. *1 ~/Work — Work done partly on on behalf of of the the Minnesota Geological Geological Survey Survey done 8 �The Biwabik Biwabik Iron-formation Iron—formationand andoverlying overlying Virginia Virginia Formation The Formation 0 SE. strike N. 25—35°E. and dip 15-35° The outcrop belt strike N. 25-35°E. and 15-35 SE. The outcrop belt of these these rocks is truncated at angle by the at a slight angle the intrusive intrusive Duluth Gabbro Gabbro Complex9 and in the northern part of the area both formations are Complex, Southward9 the iron-formation extends cut out completely. completely. Southward, extends uninteruninterruptedly down-dip beneath the overriding gabbro and Virginia FormaFormation and can can be be mined mined for for some some distance below the the outcrop by open-pit methods. the structure is superficially Although the superficially simple, simple, the the iron-formairon-formalocally faulted and and folded folded and and is is pervasively pervasively jointed. jointed. A few tion is locally steeplydipping steeply-dipping faults that strike northward and northwestward cut and displace the formation; do not exceed a few formation; maximum displacements do ofwhich whichare arerelated related to to the tens of feet. Small-scale folds, folds, some some of the northward-trending faults, faults, produce local flattening of the the beds and and belt. Two of systematic joints, subwidening of the outcrop outcrop belt. Two sets sets of systematic joints, subparallel to parallel to the major fault sets, sets, and many other joints joints occur throughthroughout the rocks at at Dunka Dunka River, River. The north— north- and northwest-trending faults and appear to regional and systematic systematicjoint joint sets sets appear to be be related related to regional stress patterns; stress patterns; most most of the other other structures stnlctures are are probably probably related to to emplacementofof the the gabbro. emplacement gabbro. 99 �STRUCTURAL CONTROLOF OFTHE TI MOUNT STRUCTURAL CONTROL MOUNT WRIGHT lrJRIGHT -MOUNT REED REED IRON IRON DEPOSITS, DEPOSITS,QUEBEC QUEBEC Peter J. Clarke J. Clarke Department of of Natural Natural Resources, Province Province of of Quebec, Quebec, Quebec, Quebec, Canada The Mount Wright Wright -- Mount Reed district, district, located located about about midway midwaySchefferville in northern Quebec, Quebec, has between Seven Islands and Scheffervifle proven to iron ore. ore. to be be an important source of concentrating grade iron The district contains the southern extension of of the the Labrador Labrador Trough, Trough, which has been deformed and and metamorphosed by the Grenville Grenville Orogeny. Orogeny. by the it is underlain by Proterozoic Proterozoje metasediments, metasediments, including gneisses, It gneisses, marble, quartzite, quartzite, iron-formation iron-formation and and aluminous aluminous schists, which rest rest marble, on a basement of remetamorphosed remetamorphosed granulite granulite and and gneiss. gneiss. Acidic and and basic intrusions are common common in in the the gneisses gneisses below below and and above above the the iron-formation respectively. The Proterozoic Proterozoic metasediments change change in in sedimentary sedimentary facies facies from near-shore deposits in the the northwest northwest to to deeper deeper water water deposits in in the the southeast. southeast. Their structural structural style style varies varies in in different different parts parts of absence of of folds folds of of the the district, district, depending on the presence or or absence depending on the presence two structural trends (northeast two (northeast to to east east and and northwest northwest to to north). north). In a part of the district relative simple simple folds of only one one trend trend dominate; in another part cross dominate; cross folds folds are are developed, and and folds folds of of both trends are are about equally equally abundant. abundant. Much of of the the valuable valuable oxideoxidefades facies iron—formation iron-formation occurs in in the the cross-.folded cross-folded zone, zone, and and the the important iron deposits lie in structural basins separated by domes of older iroD deposits lie in structural basins gneiss. \~ere Wherethe thecross-folds cross—foldsare arespaced spacedrelatively relatively uniformly, uniformly, iron gneiss. are repeated repeated at atabout aboutfour—mile four-mile intervals on a rough rough grid deposits are intervals on with axes with axes trending northeast northeast to east east and and northwest to north. north. 10 �PROTOCLASTIC BORDERSOF OFTHE THE FELSITE PROTOCLASTIC BORDERS NEAR BERGLAND, NEAR BERGLAND, MICHIGAN MICHIG.Ai~ Joseph P. Dobell and Robert W. Joseph W. Leonardson of Geology Geology arid and Geological Michigan Geological Engineering, Michigan Technological University, Houghton, Houghton, Michigan Michigan Technological University, Department rock located located along the north side An intrusive side An intrusive mass massofoffelsitic felsitic rock of Gogebic Lake near Bergland, Michigan, shows Bergland, Upper Michigan, showsdistinctly distinctly protoclastic borders at protoclastic at contacts contacts with basalt and and sandstone which indicates that the rock was at least partially solidified at at the time of emplacement. Zones showing protoclastic structure vary in width from from one to four four feet, feet, and grade away from contacts to a directionless fine fine grained felsite. felsite. The The most conspicuous features of these border zones are are aa distinct distinct banding banding resembling resembling flow flow (fluxion) (fluxion) structure or zones structure or banding, and and aa granular texture texture which which gives the the weathered sedimentary banding, sandstone or a granule conglomrock the appearance of a very coarse sandstone erate. erate. 11 �MEASUREMENT IN-SITU STRESSES SAINT MEASUREMENT OFOFIN-SITU STRESSES IN INAA SAINTCLOUD CLOUDQUARRY QUARRY A PROGRESS A PROGRESS REPORT REPORT Charles Fairhurst Charles School of Mineral School of Mineral and and Metallurgical Metallurgical Engineering Engineering University of Minnesota Minneapolis Minnesota99 Minneapolis The phenomenon is well well known known to to quarry quarry workers The phenomenon of of rock rock Iipressure;Q 'pressure is workers and often results in effects such such as undesired fracturing of blocks during quarrying. Modification Modification of of quarrying quarrying procedures procedures appears appears to to affect affect the the incidence incidence of of pressure pressure effects. effects. The paper paper describes describes surface surface strain strain gauge gauge and and borehole borehole deformation deformation measurements now now in in progress progress in in aa Saint Saint Cloud Cloud quarry quarry to to determine determine the the measurements magnitude and and orientation orientation of of the the stresses stresses considered considered to to be be responsible responsible magnitude for the pressure pressure effects. effects. The The geology geology of of the the area area is is briefly briefly described. Preliminary results results from from one one quarry quarry suggest suggest that that subsubstantial (4000 lb. (lateral) stresses stresses exist stantial (4000 lb. per sq. sq. in.) in.) horizontal horizontal (lateral) in the the directions directions suspected suspected by by the the workmen. workmen. Further Further tests, tests, which will be be discussed, discussed 9 are are planned planned to to determine determine whether the the stresses stresses are are regional regional (i.e. (i.e. externally externally developed) developed) or or residual (i.e. (i.e. internally internally developed, developed 9 for for example example during during cooling). cooling). residual Hast Hast (1958) (1958) has measured measured high high horizontal horizontal stresses stresses in in underground underground mines in in Scandinavia. Scandinavia. The major major axes axes of of the the stress stress ellipsoids ellipsoids at at various points points appear appear to to be directed directed towards towards the the center center of of earthearthquake activity in Scandinavia. Scandinavia. He He suggests regional suggeststhat that similar regional stresses may stresses may be expected expected in the the Great GreatLakes Lakes region region of ofNorth NorthAmerica. America. The possibility that the Ule stresses stressesmay may be be residual residual isissuggested suggested by by The possibility that the fact fact that thatpressure pressure effects effectsare aremost most serious serious in in the the finer-grained finer-grained the rocks. 12 �PROGRESSIVE CONTACT OF THE THE BIWABIK CONTACT METAMORPHISM METAMORPHISM OF BH1ABIK IRON-FORMATION ON ON THE THE MESABI IRON-FORMATION HESABI RANGE, RANGE, MINNESOTA MINNESOTA Bevan Bevan M. M. French Theoretical Division, Division, NASA, NASA, Goddard Space Flight Center, Center, Greenbelt, Greenbelt, Maryland Flight The Biwabik Iron-formation, on on the the Mesabi range range in in northern northern Biwabjk Iron—formation, Minnesota, is is the the middle middle unit unit of of the the three-fold three-fold Animikie Animikie Group Group of of Minnesota, Middle Precambrian Precambrian age. age. On the the eastern eastern end end of of the the range, range, the the Middle Animikian rocks have been intrusive Duluth Duluth Animikian been metamorphosed metamorphosed by the intrusive Complex; mineralogical changes changes in in the the sediments, sediments, particularly particularly Gabbro Complex; in the iron-formation, appear appear related related to to the the gabbro. gabbro. From From the the data of of the present present study, study, four four metamorphic zones zones may may be distinguished within the Biwabik Iron-formation by changes changes in in mineralogy along along the the strike strike of of the the formation formation toward toward the the gabbro gabbro contact: contact: (1) unaltered taconite taconite extends from the the western limit of (1) unaltered of the the Mesabi range range approximately approximately to to the the town town of of Aurora. Aurora. It It is is composed composed of of Mesabi quartz, magnetite, magnetite, hematite, hematite, siderite, quartz, siderite, ankerite, ankerite, talc, and and the the iron iron Of silicates chamosite, chamosite, greerialite, greenalite, minnesotaite, stilpnomelane. Of minnesotaite, and stilpnomelane. these, only quartz, quartz, hematite, hematite, chamosite, chamosite, greenalite, greenalite, siderite, siderte, and and these, some are considered considered primary. primary. The textures of of the the other other some magnetite are minerals indicate indicate aa secondary secondary origin, origin, possibly possibly through through diagenesis diagenesis or low-grade metamorphism prior to intrusion intrusion of the Duluth Gabbro Gabbro Complex. Complex. (2) (2) transitional taconite contains the same mineralogy but exhibits extensive extensive replacement replacement by by quartz quartz and and ankerite. ankerite. Incipient exhibits metamorphic changes changes in in this this zone zone are are the the partial partial reduction reduction of of hematite hematite metamorphic to magnetite and the appearance of clinozoisite clinozoisite in in the underlying underlying Pokegama Pokegama Formation. Formation. (3) (3) moderately metamorphosed taconite taconite is is characterized by development of the iron-rich amphibole amphibole grunerite grunerite and and by by the the disappearance disappearance Calcite appears from of original original iron iron carbonates carbonates and and silicates. silicates. of reaction of of ankerite ankerite and and quartz quartz to to form form grunerite. grunerite. (4) taconite, within two miles of the Duluth (4) highly metamorphosed taconite, Gabbro contact, Gabbro contact, is is completely completely recrystallized recrystallized to to aa metamorphic metamorphic fabric fabric and is composed chiefly of quartz, quartz, iron amphiboles, amphiboles, iron and iron pyroxenes, pyroxenes, magnetite, and rare and calcite. calcite. Small veins and and pegmatites pegmatites magnetite, arid rare fayalite fayalite and this zone zone may represent introduction of reported from from this represent. minor intl"odnction of material from the gabbro. gabbro. The following mineralogical mineralogical changes changesoccur occuralong alongthe the strike strike of The following of the iron-formation iron-formation toward toward the gabbro gabbro contact: contact: (a) (a) partial partialreduction reductionof ofhematite hematite to tomagnetite magnetite (in the Pokegama Pokegama Formation) Formation) (b) development of clinozoisite (in (c) formation formation of grunerite (c) 13 13 �(d) (d) (e) (e) (f) (f) (g) (g) appearance of iron-rich clinopyroxene appearance clinopyroxene (hedenbergite) (hedenbergite) disappearance of hematite appearance of ferrohypersthene appearance of graphite (from organic matter). All the changes, changes, which represent the complete complete transition from from unmetamorphosed to highly metamorphosed taconite, taconite~ occur within a a horizontal distance of of about about two two miles miles near near Mesaba. Mesaba. iron-formation Compositions of the carbonate minerals in the iron—formation by combining combining refractive refractive index index measurements measurements with with X-ray X-ray were determined by diffraction data to obtain values for for the Ca, Ca~ Fe, Fe~ and Mg components. components. In unaltered taconite, taconite~ siderite siderite compositions compositions approximate approximateCa5F'e75Mg20; Ca5Fe7y~gzo; at ankerite compositions same material compositions from from the the same material are are quite uniform at calcites that approximately Ca53Fe24Mg2j. Ca53FeZ4MgZ3. The The calcites that appear appear in in the themetameta- morphosed taconite are andand Mg—poor, morphosed taconite areFe-rich Fe-rich Mg-poor~ approximating approximatingCa9Fe10Mg1. CaB9Feld1g1. No definite change in siderite siderite or No definite change in or ankerite ankerite compositions compositions is noted along the the strike of BiwabikFormation; Formation;there there is is no indicanoted along of the the Biwabik tion of progressive progressive removal removal of of iron from from the the carbonate carbonate with increasing increasing metamorphism. By contrast, contrast~ calcites from the metamorphosed taconite increase in Ca, Ca, becoming becoming virtually virtually pure pure CaCO3 CaCO) near near the the gabbro. gabbro. The present study indicates that metamorphism of the Biwabik Iron-formation by the the Duluth Gabbro Complex was largely Isochemical i"'o~hemical and was was characterized by progressive progressive loss loss of 0fH20 H20 ;:r1d COZ. characterized chiefly by CO2. There is no indication that the original mineralogy consisted cons~sted only magnetite, or that large quantities of other components of quartz and aDd magnetite, components were introduced introduced into into the the sediments sediments from fro!ll the the gabbro, gabbro, as as has has been been proposed (Gundersen (Gundersen and and Schwartz, Schwartz, 1962). 196Z). 14 l4 �STRATIGRAPHY,STRUCTURE, STRUCTURE,fu~D ANDGRANITIC GRANITICROCK~/IN R0CK1IN THE STRATIGRAPHY, THE MARENISC0-WATERSMEE AREA, }\1ARENISCO-WATERSMEET AREA, MICHIGAN—' MICHIGAN- Crawford CrawfordE.E.Fritts Fritts Survey, Denver, S. Geological Survey, Denver, Colorado U. S. detailed mapping mapping near near Lake Lake Gogebic, Gogebic, Michigan, Michigan, reconnaissance, reconnaissance, Recent detailed Recent the Marenisco-Watersmeet area recorded by the and review of data from the Michigan Michigan Geological Geological Survey Survey since since 1900 have have led led to to reinterpretation reinterpretation of of regional stratigraphy stratigraphy and and structure. structure. The Tyler Slate of the the Gogebic regional an east—plunging east-plunging anticline anticline west west of of the the Range wraps around the nose of an lake and conformably conformably underlies aa thick thick sequence sequence of of south-dipping south-dipping metametalake and volcanic and metasedimentary rocks, rocks, which apparently underlies the the Michigamme Slate Slate (fig. (fig. 1, 1, on page). North North of Cup Cup Lake, Lake, graded graded Michigamme on next page). bedding in in quartzite formerly fornlerly interpreted interpreted as as folded folded and and overturned overturned of the the Marenisco Marenisco Range Range indicates that rocks there actually strata of are are right right side side up. up. Similarly, Similarly, near near Kakabika Kakabika Falls, Falls? pillow pillow structures structures metavolcanjc rocks indicate that strata in metavolcanic strata of the Turtle Range also also are right side up. up. The The principal structurebetween betweenMarenisco Marenisco and and principal structure Water&neet, therefore, is is aa south-dipping south-dipping monocline. monocline. Although Although Watersmeet, therefore, diamond-drill data indicate indicate aasynclinal synclinalflexure flexurenear nearBanner BannerLake, Lake, field evidence at present present does does not not require require tight tight folding field evidence at folding or largefor scale there. However, large throw throw accounts accounts for scale faulting there. However,a afault fault of large MarenisCo, and it westward disappearance the westward disappearance of of the Tyler Slate near Marenisco, is possible that that other other faults faults will will be be found found farther farther east east as as mapping mapping is continues. Rocks formerly formerly mapped mapped as as Presque Presque Isle Isle Granite Granite include include at at least least Banded gneiss three of different ages. ages. Banded gneiss three distinctive distinctive lithologic units of and a younger younger equigranular equigranular granite granite unconforinably unconformably overlain overlain by by the the Tyler Slate Slate west west of of Lake Lake Gogebic Gogebic probably probably are are pre-Animikie pre-Animikie in in age. age. Tyler Well granitic to to quartz foliated, well well lineated, lineated, biotite.-rich, biotite-rich, granitic Well foliated, monzonitic gneiss gneiss intrudes rocks rocks stratigraphically stratigraphically above above the the Tyler Tyler south and east of and probably probably is is post-Aniinikie post-Animikie in in age. age. of Marenisco Marenisco and In the Marenisco-Watersmeet area, the metamorphic grade of Animikie area, Animikie strata, in in general, general, increases southeastward toward the center of a strata, in part, part, by by the the post—Animikie post-Animikie gneiss. gneiss. It It is is broad zone zone underlain, underlain, in likely, therefore, that the the metamorphism metamorphism accompanied accompanied and and perhaps perhaps likely, therefore, of this this gneiss. gneiss. followed emplacement emplacement of ~/Work done in cooperation — Work done in cooperation with the Geological Survey Division with of the Conservation the Hichigan Michigan Department of Conservation 15 �Yondoto Falls 1]] ----~ 1]] I o 0 I I I I 2 3 4 5MILES 5 MILES I I I I I EXPLANAT I EXPLANAT zz zz «« i~ ~ Jacobsville Sandstone Jacobsville Sandstone UNCONFORMI TV UNCONFORMITY cr cr 0l0l } ::;:::;: «« 00 uu w crcr o0 0..0 ON a N zz nI Rocks Rocks near Cup Cup Lake Lake Interlayered amphibolite, Interloyered amphibolite, metogroywacke metagraywacke, phyllitic phyllilic schist, and and porphyritic schisl, parphyrilic metotuff metatuff; minor minor conglameralic quarlzite parI conglomerotic quortzite in lower part ~ cr Ol ::; « 0 u uJ w cr aa.. Keweenawan Series Keweenawan Un/CONFORM/TV UNCONFORMITY Tyler Slate Siale Graywacke.slote overlying thin Graywacke-slale thin basal basal conglomerate conglomerate £INCONFORM/ TV UNCONFORMITY Gronitic to Quartz quartz monzonitic nonzonitic gneiss Granitic to gneiss u-,,:;.~ ~, Granite Michigarnme Michigamme Slate Slate FT-T'T'll U:i±.IJ Metamorphosed pillow lavas lovos and and luffs tufts Metamorphosed pillow ~ Metatuffs Metatuffs and and metasedimentary metasedimentary rocks racks Stratigraphic Straligraphic position position uncertain; uncerlain; possibly possibly younger lhan thon pre—Animikie younger pre-Animikle granite rzJI!llJ Banded gneiss gneiss Rocks Rocks near Bonner Banner Lake Lake -1".&, phyilitic schist and and other athermetasedimentory metasedimentary phyllitiC schist rocks, undivided; undivided, may racks, may also also include include metatuff metatuff lean iron -- fa formation ~, lean r ";',0 ti an" carbonaceous slate slale • , carbonaceous Figure II. Preliminary geologicmap mapofofthe the Marenisco Marenisco —Wotersmeet area,Mlchillan, Michigan,showinll showingtentative tentative interpretation interpretation -Watersmeet area, Preliminary geologic of strotigraphy andstructure structurebybyC.C.E.E.Fritts, Frifts, 1965, of stratigraphy and 1965. �STRUCTUREAND ANDSTRATIGRAPHY STRATIGRAPHYOF OFTHE ThE KNIFE LAKE STRUCTURE LAKE GROUP GROUP EAST OF ~ HINNESOTJl:/ EAST OF ELY ELY9 MflESOTA/ John C. Green Green John C. Department of of Geology Geo1or Minnesota, Duluth University of Minnesota~ In the Gabbro Lake quadrangle just east of Ely, Lake 1.5-minute 15-minute quadrangle Ely~ Minnesota~ Precambrian Precambrian Knife Knife Lake Lake rocks rocks occur occur in in two two belts. belts. The The Minnesota, southern belt~ composed of of schist, schist, gneiss, gneiss 9 and and migmatite, is derived belt, composed from graywacke, graywacke 9 conglomerate, conglomerate 9 and and arkose, arkose~ and and is is intruded intruded and and metametathe Giants Giants Range Range batholith batholith of of .Algoman Algoman age. age. It is faulted morphosed by by the against the the basal basal part part of of the the older but but lower-grade lower-grade Ely Greenstone Greenstone against on the north north side side of of the the belt, belt, along along the the major major North North Kawishiwi Kawishiwi fault. fault. on The northern and and wider belt has been metamorphosed only to the the chlorite zone, zone. its Its contact contact with the the underlying Ely Ely Greenstone Greenstone is is with a basal conglomerate. mostly faulted, faulted, but locally conformable ~nth conglomerate. Above this this are, are, successivelY9 successively, 0-2,500 0—2,500 feet feet of of mixed mixed felsic felsic tuff and and Above elastic sediments, feetofofchloritic chloritic clastic elastic sediments, clastic sediments, 1,500_LI.,.5OO 1,500-4~500 feet sediments, mafic volcanic volcanic unit unit 0-2,250 0-2,250 feet feet thick, thick, and a thick thick a predominantly mafic sequence felsic volcanic volcanic rocks, rocks, mainly pyroclastic, pyroclastic, as as much as sequence of felsic 8,000 feet feet thick. thick. Within Within this this unit unit near near Fall Fall Lake Lake is is aa.500-foot 500-foot bed of of siliceous siliceous limestone limestone and and chert chert conglomerate. conglomerate. The felsic felsic bed volcanic rocks interfinger with mafic volcanics similar to Ely volcanic rocks with mafic volcanics to Greenstone northwest of Fall Lake, Lake, and are faulted against mafic Greenstone volcanics and sediments of unknown correlation in the northwest and north-central north—central borders borders of of the the area. area. Knife Lake time in in this this area area evidently evidently was one one of of great great crustal crustal disturbance, disturbance, with rapid erosion of the older greenstones and the rocks rocks that intrude intrude them~ them, and and extensive extensive volc&~ic volcanic activity, activity, probably mostly underwater. An active, active, island arc type of environment is envisioned. This This activity activity culminated culminated in in the batholithic intrusions intrusions and extensive faulting of the Algoman and Algoman orogeny. orogeny. *1 ~/work — Work done done ononbehalf behalf of theof Minnesota the Hinnesota GeologicalGeological Survey 16 16 Survey �PETROLOGY OF IRON-FORMATION IN THE THE REPUBLIC IlEPUBLIC PETROLOGY OFTHE THE SILICATE IRON-FORMATION MINE AREA, AREA,IVL4RQUETTE M.ARQUETTE COUNTY, COUNTY, MICHIGAN MICHIGAN Tsu-Ming Hanand and James JamesW. W.Villar Villar Tsu-Hing Han Cleveland-Cliffs Iron Iron Company, Company, Ishpeming, Michigan Michigan Cleveland—Cliffs The iron-rich metasediments at at the the Republic mine mine can can be be subsub- divided into four four lithologic lithologic types types according according to to major major mineraJ. mineral constituents. stituents. These include aa quartz-specular hematite-muscovite conglomeratic the Goodrich FOTI~ation Formation and and three conglomeratic member at the base of the lithologic types within the Negaunee Iron-formation, Iron-formation, which normally and major major reflect a close close relationship between stratigraphic stratigraphic position and mineral assemblage. assemblage. In In descending descending stratigraphic stratigraphic order order the the mineral mineral assemblages generally are: are: quartz-specular quartz-specular hematite, hematite, quartz-magnetite, quartz-magnetite, and quartz-grunerite-magnetite. The type type characterized by the and latter assemblage, assemblage, the subject subject of this study, study, is as much as 500 SOO feet thick and commonly contains a series of sill-like amphibolites. and commonly contains a series of sill-like amphibolites. The rock is typically banded as a result of compositional variations in in the the ratios ratios of of quartz, quartz, magnetite, magnetite, and and grunerite. grunerite. variations Bands Bands with with oolites oolites of of quartz-magnetite, quartz-magnetite, quartz-grunerite-magnetite, quartz-grunerite-magnetite, Locally, carbonate occurs as a and grunerite-magnetite are are common. common. Locally, major constituent of of some some bands. bands. Five generations generations of minerals are are recognized: recognized: (1) (1) scattered scattered Five grains of original elastic clastic quartz and and fine-grained fine-grained magnetite, magnetite, (2) (2) quartz, magnetite, grunerite, garnet, calcite, hornblende, and quartz, magnetite, grunerite, garnet, calcite, hornblende, pyroxene, during regional regional metamorphism, metamorphism, (3) stilpnomelane, pyroxene, formed formed during minnesotaite, hornblende, hornblende, and calcite, minnesotaite, calcite, formed during retrograde metamorphism, (4) (4) quartz-calcite, quartz-hematite, quartZ-hematite, and and an an unidentified unidentified brownish green silicate, silicate, formed as fracture fracture fillings subsequent subsequent to metamorphism, and and (5) (S) martite and hematite, hematite, formed formed from from magnetite magnetite and grunerite during supergene supergene oxidation. oxidation. Paragenetic studies studies indicate indicate that that grunerite grunerite formed, formed, at least least in part, at the expense of magnetite and quartz during metamorphism part, in the Republic mine mine area. area. This is indicated by the following observations: observations: (1) growth of gTIlnerite porphyroblasts in in nearly nearly pure pure magnetite magnetite (1) grunerite porphyroblasts bands, bands, (2) presence presence of magnetite-quartz remnants (2) remnants within within grunerite grunerite bands, bands, (3) (3) magnetite grains within grunerite bands exhibit irregular or subrounded crystal outlines in contrast to subhedral and euhedral ruagnetite in in assemblages assemblages lacking lacking grunerite, magnetite grunerite, (4) common common development development of thin grunerite grunerite layers between (4) magnetite and and quartz bands, bands, and and (S) (5) growth of grunerite along the borders of magnetite-rich veinlets that that cut cut quartz quartz bands. bands. This reaction is further substantiated substantiated by determinations of ferric ferric and ferrous ferrous iron contents of the iron—formation, iron-formation, which reveal 17 17 �the quantities of magnetite and an inverse relationship between the grunerite. This does does not not preclude preclude the the participation participation of of other other reactants reactants This such iron silicates silicates in in the the development development of of such as as carbonates and layered iron grunerite. grunerite. 18 18 �AGES MAFIC DIKES NEAR NEAR GRANITE GRANITE FALLS9 FAIJLS, MINNESOTkMINNESOTk~/ AGES OF OF MAFIC Glen and Gilbert Gilbert N. Glen R. R. Himnielberg Himmelberg and N. Hanson Hanson Department of Geology and and Geophysics University of Minnesota, Minnesota9 Minneapolis, Minneapolis9 Minnesota Precambrian rocks exposed in the Minnesota River valley near Granite Falls9 Falls, Minnesota consist of interlayered metamorphic rocks iiitruded by numerous numerous mafic dikes. intruded by dikes. Existing structures structures in in the the metametamorphic rocks rocks resulted resulted from from dynamothern-ial dynamothermal metamorphism metamorphism about 2.6 billion years years ago. ago. AA later 1.8 b.y. b.y. thermal event is reflected in potassi~~-argon potassium-argon and rubidium-strontium ages of biotite from the metamorphic rocks. rocks. The dikes can be divided petrographically into into tholeiitic diabase, hornblende hornblende andesit.e, andesite, and olivine olivine diabase. diabase. Older tholeiitic several varieties of hornblende diabase dikes are cross-cut by several andesite dikes. dikes. In addition, addition, shear shear zones, zones, which by field evidence could have formed during the late stages stages of of the the 2.6 2.6 b.y. b.y. event, event, cross-cut cross-cut the the tholeiitic tholeiitic diabase diabase but but are are cut cut by by hornblende hornblende andesite andesite dikes, dikes. One of the hornblende andesite dikes is intruded by a 1.8 b.y. granitic b.y. granitic body. body. The relative age of the olivine diabase with respect to the other dikes was not not determined determined in in the the field. field. In In this this study, study, a potassium-argon potassium-argon determination on on hornblende hornblende from from the the metamorphosed metamorphosed country rock rock gives an an age age of of 2.8 b.y., b.y., which which indicates that the hornblende was not not affected affected by by the the 1.8 1.8 b.y. b.y. thermal event. Hornblende from a tholeiitic diabase dike gives an age of 2.0 2.0 b.y.; b.y.; four four of of the the varieties varieties of of hornblende hornblende andesite andesite dikes dikes age gave concordant biotite and and hornblende potassium—argon potassium-argon ages ages of of 1.7 1.7 —1.8 b.y. b.y. the 2.0 2.0 b.y. b.y. age age is is real, real, the the shearing occurred between between 2.0 2.0 If the If, however, however, this 2.0 b.y. and 1.8 boY, ago. If, b.y. value reflects reflects the the ago. loss of argon at 1.8 b.y., b.y., the intrusion of the tholeiitic diabase and the the shearing could have taken and taken place place at at the the close close of of the the 2.6 2.6 b.y. b.y. metamorphic metamorphic event. event. ~/Work done done on on behalf of the the Minnesota Geological Geological Survey -'Work 19 19 �AI EXAMPLE OF STATISTICAL AN EXAJ.\I!.J'LE OF STATISTICAL A1\ALYSIS ANALYSIS AND AND POSSIBLE POSSIBLE INTERPRETATION INTERPRETATION OF STRUCTURAL HILL, SKANEE STRUCTURAL DATA DATA FROM FROM ARVON ARVON HILL, SKMJEEQUADRANGLE, QUADRANGLE, UPPER UPPER PENINSULA, PENINSULA, MICHIGAN MICHIGAN J. D. D. Juilland 1912-B Woodman Drive Drive Houghton, Michigan Skanee quadrangle, quadrangle, Upper Peninsula of Arvon Hill is located in Skanee Michigan, about about 13 l miles northeast Michigan, northeast of of L'anse. L 9 anse. Regionally, the area is underlain by Lower Precambrian metamorphic rocks, rocks, which which are are overlain overlain unconformably unconformably by by .Animikian Animikian metasediments. Younger glacial deposits are virtually absent except along the the flanks flanks of the the hill. hill. Five major types of rocks have been recognized in the Argon Hill area, namely, quartzite (Ajibik), gneiss, migmatite, migmatite, area, (Ajibik), aniphibolite amphibolite gneiss, granitic rock, rock, and and dioritic dioritic rock. rock. The last four rock rock types types form form the the Lower Precambrian or Archean basement; the quartzite occurs on the the basement; the flanks of of the the hill. hill. An An anticlinal structure structure is is inferred inferred from from the the distribution of the rock rock units. units. Foliations, joints were Foliations, lineations, lineations, and and joints were recorded recorded and and plotted plotted on on Schmidt nets nets for statistical analysis. analysis. Structural data data from from the the for statistical Lower Precambrian Precambrian rocks rocks were Lower were separated from those of the theAnimikian Animikian rocks. The The present-day present-day structure observed observed in the rocks was analyzed analyzed first. The Thelimbs limbsofofthe the quartzite quartzite were then rotated rotated back to horizontal. first. were then back to for the The The same same amount amount of rotation for the underlying underlying rocks rocks was used, used, thus position before rotating all structures to their theirassumed assumed position before folding folding of all structures the quartzite. These new sets sets of of readings readings were were plotted, plotted, contoured, contoured, and interpreted as as the the pre—quartzite pre-quartzite structure. structure. As indicated indicated by by BadgleyQs Badgleys Joints were were analyzed analyzed separately. separately. As Joints 'triangle of of intersection, intersection,Ii the \'triangle the joint joint system system in in the the Lower Lower Precambrian Precambrian rocks resulted two periods of stress, rocks resulted from two stress, whereas the joint joint system in the quartzite is the result result of of only only one one period, period, the the second. second. It is concluded that at least two two periods of folding affected affected the the area as a result of forces forces from from approximately approximately the the same same direction. direction. 20 �SOME IRON-FORMATIONS IN AUSTRALIA AUSTRALIA AND AND SOUTH SOUTH AFRICA AFRICA SOME ASPECTS ASPECTS OF OF IRON-FORMATIONS Gene L. L. LaBerge Gene LaBerge Postdoctoral Fellow Fellow National Research Research Council Council of of Canada Canada Canada, Ottawa Geological Survey of Canada~ The extent of Proterozoic iron-formations in the the Hamersley only recently. The Range of Western Australia has has been been recognized recognized only Range, which covers about 40,000 square miles miles,1 probably Hamersley Range~ contains more exposed exposed iron-formation iron-formation than than any any equivalent area in the the world. Three banded iron-formations having an aggregate thickness of more more than than 31500 ,5OO feet feet and, and, probably, probably~ aa total total of of more more than than 80,000 80 1000 feet sediments occur occur in in the the area. area. feet of Proterozoic sediments In South Africa, Africa, aa more more or less continuous belt of Proterozoic iron-formation that is part of the Transvaal System extends for for more than 800 miles. miles. The iron—formation iron-formation is locally more than 5,000 feet thick, thick, but is generally 800—2,000 feet 800-2 1 000 feet feet thick. thick. A A brief account account of of the the general general Proterozoic Proterozoic stratigraphy and and the stratigraphy of the iron-formations from from each each area area will will be be presented presented to to show how they differ from the stratigraphy stratigraphy of the Lake Superior iron—formations region. Layers of altered pyroclastic rocks rocks in the the iron-formations indicate indicate that that there there was was volcanic volcanic activity activity during during much much of of the the time time the iron—formations iron-formations in in each each area area were were being being deposited. deposited. the Certain features iron—formations in Western Australia features of the iron-formations and and South Africa Africa are are very very similar to to those those in in iron-formations iron-formations in in the Lake Superior region, others—-notably the occurrence of region, but others--notably crocidolite crocidoflte asbestos asbestos and and the the virtual virtual absence absence of of granules--are granules——are distinctly distinctly different. There is more similarity between Australian and South African iron-formations than there is between iron-formation of either with the Lake Superior area ~nth Superior region. region. 21 �THE IN THE THE DISTRIBUTION DISTRIBUTION OF OFMANGANESE MANGANESE IN THE BIWABIK IRON-FORMATION, BIWABIK IRON- FORt\1ATION, MINNESOTA MINNESOTA Lepp Henry Lepp Department of Geology, st. Paul Geology, Macalester College, St. The weighted mean mean Mn Mn content content of of the the Biwabik Biwabik Iron.-formation Iron-formation based on 948 individual samples samples is is 0.48 0.48 per per cent. cent. This represents represents an enrichment of about about 4.8 4.8 times times the the mean mean crustal crustal abundance abundance (Clarke) (Clarke) of this this element. element. The Biwabik shows a mean Mn/Fe ratio of 0.016 as compared to a crustal average of 0.022 for this ratio, ratio, thus indicating a slight geochemical separation separation of of Mn Mn and and Fe. Fe. Samples of iron-formation that have been oxidized without appreciable leaching or iron enrichment have considerably lower Mn/Fe ratios ratios than than do unoxidized taconites. taconites. Core samples of ores (enriched oxidized taconites containing containing more more than than 40 40 per per cent cent Fe) Fe) show only a slightly slightly lower lower mean mean Mn/Fe Mn/Fe ratio ratio than than unaltered unaltered taconite, taconite, but their mode and median for this ratio The ratio are much lower. lower. The sideritic iron—formation contain the most manganese sideritic sections of the iron-formation and the goethite-rich oxidized sections sections contain contain the the least. least. There appears appears to to be be no no significant significant variation variation in in the the Mn content content There of the Biwabik laterally if only only unoxidized samples samples are are considered. considered. There is, is, however, however, a significant significant difference between the the four four members; members; the means in in per per cent cent Mn Mn are are as as follows: follows: Lower Cherty Cherty -- 0.67, Lower Lower Slaty -. Slaty - 0.44, Upper Cherty Cherty -- 0.34, Upper Slaty Slaty - 0.29. In an attempt variations in in the the Mn content content aa attempt to to show the local variations trend surface surface was computed for an an area area with closely closely spaced spaced holes. holes. The trend surface f(TJ,V,W) ) accounts for 52 per cent surface (%Mn (%Mn == Xn = f(U,V,W) of the sum sum of of squares. squares. Deviations from from the trend surface surface cut cut across across thus suggesting of the variability the formation formation thus suggesting that some some of variabilitymay may be be the secondary oxidation planes. due to due to secondary oxidation and and leaching leaching along along joint joint planes. ) 22 �SOME ASPECTS SOME ASPECTSOF OFTHE THEPEGMATITES PEGNATITESIN IN THE THE FELCH FELCH DISTRICT DISTRICT,9 DICKINSON DICKINSON COUNTY, COUNTY, MICHIGAN HICHIGAN Geoffrey W. Geoffrey W. Mathews Mathews Department of Geology Department Geology University, Cleveland, Cleveland, Ohio Western Reserve University, cut the the pre-Animikian Numerous simple, simple, unzoned un zoned pegTnatites pegmatites cut units in in the the Feich Felch district. district. Size and shape shape of of the the metamorphic units pegmatites vary from small small sinuous sinuous bodies in the the Mill Pond Granite Gneiss to to large large irregular irregular masses masses in in the the Solbert Solbert Schist. Schist. to subdivide the the pegmatites into meaningful In an attempt attempt to groups, pegmatites groups, the Be, Be, Mo, Mo, and and Ti contents of twenty unclustered pegmatites were determined determined spectrographically. spectrographically. Ratios of the concentrations of of these these elements elements provide provide aa basis basis for for separating separating the the pegmatites pegmatites into into two two distinct distinct groups. groups. AA similar similar analysis analysis was run on the granite granite dikes and samples of of the the granite granite gneiss gneiss in in the the Feich Felch district. district. Seven of and samples the pegmatites (Group II pegmatites), pegmatites), characterized by a relatively relatively high Ti:Be+Mo ratio, ratio, plot in in the the same same area area of of aa relative-percent relative-percent triangle diagram as the Group the granite granite dikes dikes and and the the granite granite gneiss. gneiss. Group comprisingthe the remaining remainingthirteen thirteen of the II pegmatites, comprising the pegmatites pegmatites and characterized by by a relatively relatively low low Ti:Be+Mo ratio, ratio, plot plot in in aa distinctly different different region region on on the the diagram. diagram. Correlation coefficients coefficients Be—Mo, Be-Ti, Be-Ti9 and Mo-Ti Mo—Ti also emphasize the difference between between Be-Mo, the two groups. groups. Group II pegmatites and the the granite dikes and gneiss show small small positive positive correlations between Be Be and Mo Mo and relatively show large negative correlations between Be-Ti and and Mo-Ti. Ho-Ti. Group II II pegpegmatites have a large positive correlation between Be-Mo and small small correlations between Be-Ti and Mo-Ti, positive and and negative negative respectively. respectively. Mo-Ti, positive There appears to to be be no simple simple relation relation between geographical geographical loca.tion, size, size, shape, shape, or or host host rock rock unit unit and and the the two two groups groups of of location, pegmatites. The strikes strikes of of bodies bodies within within the the different different groups, groups, however, are divergent. divergent. Strikes of Grou.p Group II pegmatites are are confined confined however, are 0 E., to the range N. 80° E., whereas the the strikes of Group II to N. 300 30 0 E. E. -- N. 80 peginatites are seemingly haphazard. pegmatites are haphazard. It is suggested suggested that the in the the Felch the two two groups groups of pegmatites in district district represent represent either either (1) (1) different different parental parental sources, sources, or or (2) (2) intrusion at at different stages stages of of the the progressive progressive differentiation differentiation of of intrusion a single parent magma under different different tectonic tectonic controls. controls. 23 23 �LAKE COUNTY, THE SAUBLE SAUBLE GEOPHYSICAL GEOPHYSICAL ANOMALY, ANOMALY, LAKE COUNTY, MICHIGAN MICHIGAN THE Howard J. J. Meyer and Howard and William J. J. Hinze of Geology, State University, Geology, Michigan Michigan State University, Lansing, Michigan Michigan East Lansing, Department Department A detailed gravity and magnetic survey was conducted of the A Sauble anomaly of Lake County, County, Michigan. This outstanding outstanding anomaly anomaly is a circular magnetic and gravity high having residual maximum and 22 22 milligals milligals respectively. respectively. The The comcomamplitudes of 1,130 gammas and bined gravity gravity and and magnetic lnagnetic analysis analysis method method utilizing utilizing Poisson's equation was applied applied to to the the residual residual anomalies, anomalies. An idealized idealized case case was employed employed to to check check the accuracy accuracy of of the the combined combined analysis analysis method. method. form, size, The composition, composition, form, size, and depth of the anomalous body were studied further by depth determinations and by fitting idealized cases to the observed anomaly anomaly profiles. profiles. It was concluded that that the the anolnalous body body is is a very basic Precambrian intrusive stock. The anomalous The the body and the the Precambrian surface in this elevation of the top of the area is about 8,000 to 99000 feet below 9,000 feet below sea sea level. level. 24 �THE THE SEDINENTOLOGY SEDIMENTOLOGY OF THE THEPRECAMBRIAN PRECAMBRIAN ROVE ROVE FOPUATION FORMATION NORTHEASTERN MINNESOTA-! MINNESOTA~/ IN NORTHEASTERN G. B. Moray Morey G. B. Department of Geology Geology and and Geophysics9 Geophysics, University of Minnesota9 Minnesota, Minneapolis The Middle Middle Precambrian Rove Formation, the upper part of the the The Formation, the Aninikie Group, Group, is estimated to to be at least 3,200 feet thick, Animikie thick, and is and the is exposed between northwestern Cook County, County, Minnesota Minnesota and Thunder Bay is aa sequence sequence of of gra~~acke, grayacke, Bay district, district, Ontario. Ontario. It is argillite, locally abundant argillite, abundant intraformational intraformational conglomerate, conglomerate, quartzite, quartzite, and carbonate carbonate rocks. rocks. This sequence was deposited some some time between 2.0 b.y. b.y. ago in a northeast-trending basin, b.y. and 1.7 b.y. basin, the the conconfiguration of which which was was probably controlled by a pre-existing pre—existing figuration structural structural grain. grain. Detailed mapping in the South Lake 7*-minute 7i-minute quadrangle, quadrangle, combined with a field and laboratory study study of approximately 150 other scattered stratigraphic stratigraphic sections provide provide aa basis basis for for the the recognition of four informal lithologic units. units. From oldest to to youngest these these are: are: (1) lower argillite, (1) argillite, 400 feet thick; (2) (2) transition transition beds beds of of inter— interbedded argillite and graywacke, grayacke, 70 argillite and 70 -- 100 feet feet thick; thick:; (3) (3) thin-bedded graywacke, gra~Nacke, as much as as 2,000 feet thick; thick; and (4) (4) upper graywacke— gra~Nacke­ quartzite, at least 700 feet quartzite, feet thick. thick. It is concluded that the argillite argillite and and associated associated graywackegraywackesandstone and and graywacke-siltstone graywacke-siltstone units units were were deposited deposited in in moderately sandstone deep, quiet quiet water water which which was was probably probably marine. marine. Repeated sedimentation sedimentation deep, units one to three feet thick indicate indicate sediment sediment transport and and deposition A sedimentation unit reconstructed deposition by by turbidity turbidity currents. currents. A from composite sections sections consists of (1) (1) a basal conglomeratic gray— graywacke, (2) wacke, (2) aa structureless structure1ess unit unit that that grades grades indistinctly indistinctly into into (3) (3) a graywacke that that is is overlain overlain by by (4) (4) aa laminated laminated graywacke, graywacke, graded grayvJacke by (5) (5) small-scale cross-bedding, or or (6) (6) conwhich may be modified by torted one or several torted bedding. bedding. Any Anyone several of these may be absent, absent, but the argillite. unit unit is is always always overlain overlain by by (7) (7) an argillite. Post-depositional Post-deposition31 soft-sediment soft-sediment structures structures such such as as load load casts, casts, flame structures, clastic dikes, dikes, bed pull-aparts, pull-aparts, overfolds, overfolds, and flame structures, clastic micro-faults micro—faults indicate indicate rapid rapid deposition of of Rove sediments, sediments, active active bottom currents, and post-depositional post-depositional deformation. deformation. A A detailed analysis analysis of of paleocurrent directional indicators indicators such such as groove casts, casts, flute flute casts9 casts, dendritic dendritic ridges, ridges, as grain lineations, lineations, groove and and cross-bedding show that the turbidity currents had a southerly southerly trend perpendicular perpendicular to to the the axis ~xis of of the the Rove Rove basin. basin. However, ripple ripple marks, winnowed lag deposits at at the the tops tops of many graywacke graywacke beds9 beds, and festoon-type festoon-type cross-bedding show that the the turbidities were later modified by by bottom currents currents that that trended trended southwesterly southwesterly parallel parallel to to the axis of the the basin. basin. —'Work ~/Work *1 done the Minnesota Geological Survey Survey done on behalf of the 25 �The heavy minerals of of the the Rove Rove are are characterized characterized by by epidote— epidotegroup minerals, sphene, and tourmaline~ minerals, apatite, apatite, sphene, tourmaline, and are typical of pre-Middle Precambrian igneous rocks now exposed north of the present outcrop area of the Rove Formation. Formation. Thin section and and X-ray analyses of 200 200 samples show that the the angular, poorly sorted grains of elastic graywackes consist of angular, clastic quartz and plagioclase (niü_An25) embedded plagioclase (AnlO-An25) embedded in in an an argillaceous argillaceous matrix matrix that now consists of quartz, chlorite, chlorite, and and muscovite. muscovite. The finefinegrained, fissile fissile argillite argillite and mudstone have have the the same grained, srone mineralogy and micro-textures micro-textures as as the the graywacke. graywacke. to pre-Keweenawan tilting removed an unknown Erosion subsequent subsequent to the formation formation prior to the the deposition of Lower Keweenawan amount of the sedimentary rocks. rocks. The intrusion of Middle Keweenawan igneous rocks sedimentary Rove Formation to to a variety of caused local metamorphism of the Rove mineral, assemblages now now assigned assigned to to the pyroxene- and mineral assemblages and hornblende— hornblendehornfels facies, hornfels facies, but but the the remainder remainderisisessentially essentiallyunnieta.morphosed. unmetamorphosed. 26 26 �SEDIMENTATION OFOFMIDDLE FINLAND SEDflVIENTATION MIDDLEPRECAMBRIAN PRECJMBRIANQUARTZITES QUJRTZITES IN IN FINLAND Richard W. W. Ojakangas Department Departmentof of Geology, Geology,University University of Minnesota, Minnesota, Duluth quartzites, metamorphosed 1,800 m.y. m.y. ago, The Jatulian quartzites, ago, were studied in in eastern, eastern, central, central, and and northern northern Finland Finland to to decipher decipher the the studied sedimentary history of the the original original sandstones. sandstones. Erosional remnants remnants thick, indicate an initial of the formation, formation, several hundred meters thick, distribution over over an an area area of of about about 400,000 400,000 km2. km2. The quartzites at at some localities localities are are completely completely recrystallized~ recrystallized; at at other other localities localities some they are are sheared sheared but but retain retain sedimentary sedimentary characteristics. characteristics. Most Most of of the quartzites were formed under the under conditions conditions of of the the amphibolite amphibolite facies, facies, with the degree of metamorphism increasing from east to west. west. The sandstones sandstones were mainly clayey orthoquartzites, orthoquartzites, clayey subsubarkoses, arkoses, and and clayey clayey arkoses. arkoses. The clayey matrix has been recrystallized into Zircon is is the the only abundant nonopaque nonopaque detrital heavy into mica. mica. Zircon mineral; mineral~ most other heavy minerals were formed formed during during metamorphism. metamorphism. The source rocks were mainly granitic with indeterminate proporproportions of granites and and gneisses. gneisses. Zircon varieties indicate derivation from both para- and ortho-gneisses. Large parts of the formation are mineralogically and tex~urally evidently detritus on on the the are texturally mature; mature; evidently weathered, vegetation-free vegetation-free landmass, as well as as similar similar sediment sediment landmass, as supplied by by streams streams from from the the east, east, was was reworked reworked by by wind wind and and then then by by supplied the shallow shallow sea. sea. Clay was probably carried carried into the sea sea vuth with quartz sand, sand, separated separated there there by by wave wave and and current current action, action, and and then again again mixed mixed with with sand sand prior prior to to burial. burial. Carbonates and shales shales were deposited deposited upon the sandstones. upon the sandstones. Analysis of of cross-bedding indicates that the the major paleocurrent Analysis movement in the Jatulian Sea was toward the west-northwest, with a prominent current current movement movement toward toward the the south-southwest. south-southwest. secondary but prominent secondary One of these currents probably moved parallel to the shoreline shoreline and the other other normal normal to to it. it. The The sea sea probably probably transgressed transgressed eastward eastward upon upon the a stable, stable, low-lying low-lying landmass. landmass. 27 �PETROLOGYOF OFTHE THE AMBERG M'ERG PRECPJYRIAN PETROLOGY PRECAMBRIAN CRYSTALLINE CRYSTALLINE COMPLEX, NORThEASTERN NORTHEASTERN WISCONSIN WISCONSIN COMPLEX, Dennis P. Rebello P. Rebello Department of Geology Western Reserve University, University, Cleveland, Cleveland, Ohio Reconnaissance study study of of parts of of northeastern Wisconsin by J. A. A. Cain and Quinnesec J. and others has resulted resulted in in recognition recognition of the Quinnesec Formation, pink mberg AmbergGranite, Granite,and andgray grayAniberg Amberg Granite. Granite. Detailed Formation, mapping of approximately approximately 100 square square miles during the summer summer of 1964 has has resulted resulted in in the the identification identification of of an an additional additionalunit, unit, the the.Amberg Amberg addition, diabase and basalt dikes were found found Granodiorite. In addition, cutting the the granitic granitic units. units. The Quinnesec Formation Formation include include greenstones greenstones and and meta-basalts, meta-basalts, which contain contain plagioclase plagioclase and and hornblende hornblende and and minor minor amounts amounts of of chlorite, chlorite, epidote, epidote, and and quartz. quartz. The unit is is exposed exposed along along the the north north and and northnortheastern boundaries of this area area and and in in aa small small triangular patch patch south south of of Amberg. Amberg. The major part part of of the the area is underlain by the the pink Amberg niberg The Granite, which is Granite, is circular circular in in outline. outline. The rocks rocks are are fresh, fresh, massive, massive, coarse-grained coarse-grained pink pink granites. granites. Locally they they have aa rapakivi rapakivi tex±ure. texture. Xenoliths of Quinnesec Formation and gray Amberg _~berg Granite are are not microcline-perthite, sodic uncommon. The rocks are are composed of microcline-perthite, sodic oligoclase, quartz, biotite, and and hornblende. hornblende. Minor Minor shear shear zones zones are are present. Lineation and foliation are are poorly poorly developed. developed. The The unit unit intrudes the the gray gray J3mberg Amberg Granite, and the the Granite, Amberg Amberg Granodiorite, and Quinne sec Formation. Formation. Quinnesec The gray gray Amberg is exposed exposed in the center center of of the the area area Pmberg Granite is and is almost surrounded surrounded by by the the pink pink unit. unit. It consists consists of of fresh, fresh, massive, massive, medium- to fine-grained gray gray granites granites composed composed of of orthoclaseorthoclaseperthite, oligoclase—sodic oligoclase-sodic andesine, andesine, quartz, quartz, biotite, biotite, and and hornblende. hornblende. The rnberg Amberg Granodiorite Granodiorite covers covers most most of of the the southeastern southeastern part part of of The the area. area. It is is coarse-grained, coarse-grained, altered, altered, and and has abundant abundant xenoliths xenoliths of the Quinnesec Formation. Formation. Shear zones and mafic schlieren schlieren are are common throughout the unit. The rocks consist of orthoclase—perthite, orthoclase-perthite, oligoclase—andesine, quartz, biotite, oligoclase-andesine, biotite, and ffild hornblende. hornblende. Modal analyses analyses and and chemical chemical analyses analyses for for alkalies alkalies suggest suggest that that the the granitic units units represent represent independent independent intrusions. intrusions. Field Field and and petrographic petrographic data data point point to to aa m.agmatic magmatic origin for for the the granites. granites. 28 �A STUDY ON ON THE THE HYDROLOGY MINNESOTA~I A STUDY HYDROLOGYOF OFPOTHOLES POTHOLES IN IN MINNESOTA- M. Schwartz Schwartz George M. Professor Emeritus, Department of Geology Professor Emeritus, Department University of of Minnesota, Minnesota, Minneapolis study of of the hydrology of potholes (ponds) (ponds) in Minnesota by A A study the writer and and associates associates has has been been carried carried out out since since 1962. 1962. Potholes and adjacent adjacent lakes were selected selected in in various parts of the state state to and to represent as as many different topographic and geologic situations situations as as represent practical. Detailed Detailed observations observations were were made made on on 39 39 potholes and and lakes lakes and limited observations on about about 60 60 others. others. The field field work included sinking sinking test holes adjacent to shore shore to determine the the character character of of the the soil soil and and the the depth depth of of the the water water table, table, observing the the water (and (and ice) ice) levels levels in in the the ponds, ponds 9 collecting collecting bottom bottom observing sediments, the bottom sediments according sediments, and classifying samples of the to soil soil type. type. Limited X-ray X-ray and and pollen pollen studies studies of of selected selected samples samples also made. made. Cross-sections Cross-sections and and graphs graphs were prepared prepared of of all all were also pertinent pertinent data. data. Tentative results results and and conclusions conclusions include include the the following: following: 1. The glacial deposits adjacent to the water are extremely 1. are reasonably permeable as variable lithologically, but but most. most are as shown shown by movement of water out of of test test holes. holes. 2. No consistent consistent relation relation exists exists between the open open water surface surface 2. No and the the groundwater surface surface except except in in the the Anoka Anoka Sand Sand Plain. Plain. 3. Most of the the ponds and and lakes show show a similar similar pattern pattern of of 3. fluctuation of of the the water water levels levels throughout throughout the the year. year. Li. 4. With few exceptions, al'e exceptions, the water levels in the ponds are determined mainly mainly by by the the relation relation of of precipitation precipitation to to evapotranspiration. evapotranspiration. 5. In highly permeable soil, soil, such such as as in in the the Anoka Anoka Sand Sand Plain, Plain, 5. the surfaces coincide and fluctuate the open water and groundwater surfaces fluctuate together by movement of water water from one one to to the the other as required by Li, 4, above. 6. 6. Most lakes and potholes do not contribute significant significant quantities of water water to to underground underground storage. storage. The bottoms of potholes normally consist of silt, 7. silt, clay, clay, and 7. organic matter. 8. S. In ponds ponds that that lose lose water water by by seepage, seepage, the the water water level level rises rises during the the spring spring break-up and periods periods of heavy rains, rains, then then declines declines far beyond possible possible loss loss by by evapotranspiration evapotranspiration and and continues continues to to far freeze—up; collapse of the ice occurs in severe decline after the freeze-up; cases of loss loss of of water. water. In contrast, remain relatively relatively contrast, most ponds remain stable while covered covered by by ice. ice. — Funds to :/Funds to start start the program were made available in 1962 by the the Minnesota State State Soil Soil Conservation. Conservation. Supervision of the project project and and funds were were provided by the Department of Agricultural additional funds Engineering. 29 �PRELIMINARY RESULTS OF GEOCHEMICAL GEOCHEMICAL PROSPECTING PROSPECTING PRFJJIMINARY RESULTS OF NORTH NORTH OF OF THE THE MARQUETTE MARQUETTE IRON IRON RANGE9 RANGE? MICHIGAN MICHIGAN Kenneth Segerstroni Kenneth Segerstrom Survey, Denver? Denver, Colorado U. S. Geological U. Geological Survey? Colorado material Geochemical prospecting by means of sampling of surficial material has been conducted in Marquette County during the past two field field seasons. More than 600 samples samples have been collected and and chemically chemically analyzed for for their their total total heavy-metals heavy-met~_s content. content. Many of the samples samples were also analyzed analyzed for copper, copper? lead, lead? zinc, zinc, and manganese, manganese? and and some some samples were examined examined spectrographically for for cobalt? cobalt, nickel, nickel, and other other elements. elements. AA few few were assayed assayed for for gold gold and and silver. silver. Preliminary results resultshave have encouraged encouraged the the continuance continuance of ofsampling sampling Preliminary in so-called Northern 11Northern Range, Range?:1 just justnorth northofofthe theDead Dead River River in the so-called discouragedits its continuance in the the Southern storage and have continuance in 11Southern storage basin, and have discouraged Range," between between the the Dead Range," Dead River and and the the Marquette Iron Range. Range. In the the Northern Range Range good good results have been been obtained obtained on on the the lee lee side, side, Northern glacially speaking, of ridges ridgesofof resistant pre-Animikiegraywacke graywacke speaking, of resistant pre—.Animikie and volcanic volcanic rocks rocks which whichlie lie on on the the limbs limbs and and crest crest of an an anticlinoriuni. anticlinorium. and The ridges ridges are are bordered to the north and and south south by synclinal synclinal valleys underlain by by poorly ridges tend tend poorlyresistant resistant slate. The The stoss stoss side side of ridges to have have a thick till cover and the valleys are deeply filled ~nth with to glaciofluvial sand. glaciofluvial sand. Soils underlain by the sand do the till and the sand not not show show concentrations concentrations of of heavy heavy metals. metals. The best results are are obtained where the cover of of surficial surficial materials materials (chiefly (chiefly glacial) glacial) colluviun derived is thin, thin, and and where where there there are are abundant abundant adrnixtures admixtures of of colluviu..m is from from the the bedrock bedrock ridges. ridges. Anomalous copper and and lead or zinc, Anomalous concentrations concentrations ol' of copper zinc, of of the the order of hundreds of parts per million, million, have shown up in samples samples taken in Nt N sec. sec. 30, 30, T. T. 49 49 N., N., R. R. 27 27 W. W. In that area area of of no no mines mines or or prospects, the exposed bedrock locally contains fine—grained prospects, fine-grained disseminated pyrite and galena. galena. In In the same same township, township, lesser anomalies anomalies that that are are likewise likewise apparently unrelated unrelated to to known known sulfide sulfide SE- sec. deposits have shown up in SEt sec. 21, 21, NW sec. sec. 27, 27, &3- sec. 26, 26, and N'vJt NT4 sec. sec. 36. 36. NWt 30 st �KEWEENAWFAULT, FAULT, HOUGHTON COUNTY, MICHIGAN KE"WEENAW HOUGHTON COUNTY, MICHIGAN Kiril Kiril Spiroff Michigan Michigan Technological Technological University, Universitys Houghton, Michigan wifl describe a few of the geologically The talk will geologically interesting interesting features found found associated with the features the Keweenaw Fault in Houghton County, Michigan. 31 31 �__________ _______ ORGANIC GEOCHEMISTRYOF OF ROSSBURG,llEAT ROSSBURGPEAT BOG, ORGA1'HC GEOCHEMISTRY BOG 9 AITKIN COUNTY, COUNTY 9MINNESOTA—' MINNESOTA- F. M. M. Swain 9 Mykola Swain, Mykola MalinowskY9 Malinowsky, and and David Nelson of Geology Geology and and Geophysics, Geophysics, Department of of Minnesota Minneapolis University of Minnesota,9 Minneapolis sees. 18 and and 19, 19~ Rossburg peat bog occupies about 600 acres in secs. T. 47 N., R. R. 25 W. W. and sec. T. sec. 24, T. 47 47 N., N. 9 R. R. 26 26 W., W., Aitkin Aitkin County, County, Minnesota. Minnesota. Coarse-detritus, Coarse-detritus 9 reddish brown Sphagnum moss peat exbends extends to depths of of from from 12 12 to to 19 19 feet feet and and is is underlain underlain by by fine-detritus, fine-detritus 9 to dark brown to black copropel, coprope1 9 and and sapropel-peat sapropel-peat to to depths of of 22 22 feet feet or more. more. Below the peat lies slightly slightly calcareous calcareous and and organic organic clay clay to depths of 27 feet to feet or or more, beneath beneath which which lies lies sand. sand. Moisture content content of the peat peat is is 85-90%; 85-90%; that of of the the underlying clay 50-68%, 50-68%9 and and of of the the sand sand 34%. 34%. Ignition loss ranges from 67.6% clay to 96.5% in the the peat and from 11.0% 11.0% to to 15.5% 15.5% in in the the clay clay and and sand. sand. pH values increase increase gradually from from 4.0 at at the surface surface of of the the peat peat to to the peat and are about 6.8—7.0 7.2 at the base of the 6.8-7.0 in the clay and sand. Eh values gradually decrease from from +420 mv at the the surface surface of of sand. Eh my at my at 28 feet the peat to -20 mv feet in in the sand; sand; in in general, general 9 Eh values values are are negative below below 16 16 feet feet in in the the peat. peat. negative Kjeldahl nitrogen K.jeldahl nitrogen averages averages about about 1% i% in the upper 33 feet of the peat, 2.8%; it decreases peat 9 below which it increases to between 1.8% and 2.8%; abruptly to 0.5% or less in in the the underlying underlying clay. clay. Protein amino amino acids show distribution consistent with with variations in type of peat and nitrogen nitrogen content. content. Basic Basic amino amino acids occur throughout the the peat peat and and indicate prevailingly prevailingly acid acid conditions conditions in in the the history history of of the the bog. bog. Total carbohydrates average about about 100 mg/gm expressed as as glucose glucose equivalent in Sphagnum peat, peat, but decrease to 50-70 mg/gm mg/gm in in copropelic coprope1ic peat. peat. Glucose Glucose and and arabinose arabinose are are the the predominant predominant mononaccharides. mononaccharides. aromatic hydrocarbons and hydrated phenols increase Saturated and aromatic in total amount from 2x10—4 mnount from 2xlO- 4 g/g gig at at the the surface surface of of the the moss moss peat peat to to 4 4x104 gig ',4x10g/g at 44 feet, feet, below below which which a decrease decrease occurs to base of moss peat. Absorption Absorption spectra spectra of chromatographic chromatographic fractions fractions show show that that 2-naphthol 2-naphthol is is an an important important hydrocarbon hydrocarbon constituent constituent of of the the moss moss peat. peat. It It is 4_s suggested suggested totohave haveformed formed either either froma protein—naphthylamine a protein-naphthylamine from by by Bucherer Bucherer reaction: reaction: NH3 (NH4)2 4 ,OH ;' .: "',-" :.:-, NH 22 i: ~ .' ~, ;:;..-~ +H 0 2 or from from aa plant-growth plant—growth accelerator (auxin) (auxin) such as naphthyiacetic naphthylacetic acid: acid: CH2 COOH CH 2 CO OH ~:; .......... ~/Work Work i ...-., :1 "1 :1 b~~aif~of 1 done partly partly on behalf of the the Minnesota Geological Geological Survey Survey done 32 32 �Beta-carotene Beta-caroteneasas observed observedininUV-visible UV-visiblespectra spectraisis aa significant componentofofthe thecopropelic copropelicpeat peatbut but is is nearly absent component absent from from the overoverlying moss It isisinterpreted originating from moss peat. It interpretedasas originating fromphytoplankton phytoplankton whenthere therewas wasa alake lakein in the the area. Pheophytini!:a from when area. Pheophytin from chlorophyll relationship to to facies fades of of the the peat. peat. shows a similar relationship Carbonyl-group compounds observed in IR spectra are are quantitatively more important in the moss peat than in in the underlying lake peat. peat. The organic analyses aid aid in in understanding the developmental the deposits deposits and in evaluation of them history of the them as as commercial commercial of plant nutrients sources of nutrientsand and peat peatchemicals. chemicals. sources 33 �TECTONICS OF THE THEKEWEENAWAN KEWEENAWAN BAS~N, TECTONICS OF BASN, WESTERN LAKE SUPERIOR REGION-SI REGION~/ WESTERN LAKE SUPERIOR ~valter S. S. White ~Jhite Walter U. S. Geological Geological Survey, Survey, Beltsville, Maryland U. S. Beltaville, Maryland The subsurface of the thewestern western Lake Lake Superior Superior region region The subsurface structure structure of has been analyzed by combining surface surface geologic, geologic, aeromagnetic, gravity, and paleomagnetic paleomagnetic data. data. Surface attitudes and and map map patterns patterns gravity, and suggest that the Keweenawan sedimentary rocks have the general the upper Keweenawan form of a lens thickening to southeast, away from aa featheredge featheredge to the the southeast, along the shore of of Lake Lake Superior. Superior. Graphic subtraction subtraction of the Minnesota shore the assumed gravitational effect of this sedimentary lens from the Bouguer anomalies anomalies of of the the region region leaves leaves aa residual residual anomaly anomaly due due primarily to to the the mafic mafic lavas lavas and and intrusives. intrusives. When residual maps for various assumed thicknesses of the sedimentary sedimentary rocks are compared with the the aeromagnetic aeromagnetic maps, maps, the the patterns patterns more more or or less less coincide coincide when when with the thickness thickness of sedimentary sedimentary rocks rocks under the the Bayfield Peninsula Peninsula is is the The analysis leads to recognition assumed assumed to to be be at at least least 25,000 25,000 feet. feet. of the following stages stages in in the the tectonic tectonic history history of of the the region: region: (1) Accumulation, Accumulation, during during middle middle Keweenawan Keweenawan time, time, of a thick thick (1) series of lava flows and and mafic intrusives intrusives in in two two basins basins or or troughs, troughs, separated separated by a positive positive area area that that trends trends more more or or less less north-south north-south across the Bayfield. Peninsula, Wisconsin, Wisconsin, in which which the lavas Bayfield Peninsula, lavas are are thin or or absent. absent. (2) Evolution Evolution of of the the present present Lake Lake Superior basin, basin, with with axis axis (2) trending northeast, late Keweenawan Keweenawan time. time. northeast, during late the Ashland syndilne (J) syncline and the major faults (3) Development of the Keweenaw, Lake Owen) Owen) still later in of the region (Douglass, (Douglass, Keweenaw, Keweenawan time. time. the Duluth Gabbro Complex is a sheet of fairly uniform If the Duluth Gabbro thickness dipping to to the the southeast under Lake Superior, Superior, the the combined combined thickness of gabbro should attain a maximum somewhere somewhere gabbro plus lavas should under under the the lake. lake. The gravity maximum is actually about 10 miles northwest of the Minnesota shore shore of the lake, lake, suggesting that that the gabbro pinches out out beneath beneath the the lavas lavas somewhere somewhere near near the the shore. shore. ~/Published with the permission of of the Director, U. S. S. Geological Geological — Published with Director, U. Survey Survey 34 34 �CONTRIBUTIONS CONTRIBUTIONS OF ROCK ROCK PHYSICS PHYSICS TO TOGEOLOGY GEOLOGY Robert J. J. Willard Robert Willard u. S. S. Bureau of Mines, Mines, Minneapolis Minneapolis U. Laboratory Laborato~ study study of rock rock behavior behavior can be a useful guide to to understanding understanding of of rock rock behavior behavior in in the the field. field. A goal of of rock rock physics physics A goal research at the the Bureau of Mines Mines Minneapolis Center is the identificaidentification, tion, classification, classification, and definition of rock and mineral properties that influence behavior behavior under under laboratory-imposed laboratory-imposed stresses. stresses. AA signifisignifithe current research effort involves petrographic petrographic analysis analysis cant part of the of rock fabric fabric in in core core samples. samples. material can can be be regarded regarded as as having having some some degree degree of of Most rock rock material Most fabric anisotropy, anisotropy, as expressed by population parameters of mineral species, species, aa tangible end-product end-product of of geologic geologic history. history. Such parameters of compositional anisotropy may at times be reflected in the mechanical response stresses. response of laboratory specimens to artifically-created stresses. example, tensile failure For example, failure studies in such rocks as granite and gneiss show show definite of fracture fracture path characteristics characteristics definite correlation of with fabric anisotropism, as expressed in in feldspar, feldspar, amphibole, amphibole, mica, and quartz. quartz. Similarly, Similarly, field correlation exists for for rocks having rift, grain, grain, bedding, bedding, or other planar features, features, resulting in fracture rift, fracture patterns patterns which which are are used used to to advantage advantagebybyquarr3nnen. quarrymen. Shear failure, failure, on the other hand, hand, is not necessarily related related to fabric anisotropy. anisotropy. Inclusion of fabric study can supplement supplement fabric anisotropism in field field study correlation of of deformed deformed and/or and/or fractured fractured rock rock material material with stresses correlation to which it has been subjected during its geologic history. history. Such Such fabric study study can can be facilitated facilitated by by petrographic petrographic work without without use use of of fabric Thus, by making thin sections normal to to core axes a U—stage. U-stage. Thus, a drilled from field-oriented rock in in three, three, mutually-perpendicular directions, a three-dimensional three-dimensional picture picture is is obtained obtained of of fabric fabric directions, a anisotropy such such as, as, e.g., e.g., foliation. foliation. Rock physics is using this anisotropy approach in the the testing testing of an oriented block from the the St. approach st. Cloud area to correlate fabric fabric anisotropy anisotropy with with field field anisotropy. anisotropy. 35 35 �AN AEROMAGNETIC AEROMAGNETIC SURVEY SURVEY OF WESTERN \,oJESTERN LJ\KE LAKE SUPERIOR J\N Richard J.J. Wold Wold Department of of Geology, Geology, The University of Wisconsin, Wisconsin, Madison, Madison, Wisconsin In March 1964, over the the l96'4, an an aeromagnetic aeromagnetic survey survey was was conducted over western half half of of Lake Lake Superior, SUperior, covering covering the the area area westward westward from from the the tip tip of of the the Keweenaw Keweenaw peninsula peninsula to to Duluth, Duluth, Minnesota. Minnesota. The survey survey concon7,500 miles miles of north-south flight flight lines spaced at six-mile sisted of 7,500 intervals. A intervalS. A digital recording proton precession magnetometer system system installed in in aa Navy Navy P2V-5 (Neptune) (Neptune) aircraft, aircraft, flown flown 3,000 feet feet above above sea level, in the survey. survey. level, was used in The results results of the survey survey indicate indicate aa very very flat flat magnetic magnetic character character over the the major major portion portion of of Lake Lake Superior. Superior. Several known geologic features are are traced traced by the anomalies: the the Keweenaw, Keweenaw, Douglas, Douglas, the magnetic anomalies: and Lake Owen faults, faults, and and the the Gogebic Gogebic and and Marquette Marquette iron iron ranges. ranges. The existence of the the Isle Royal fault appears to be confirmed, confirmed, and possibly it it extends extends as as far far east east as as Superior Superior Shoals. Shoals. The The existence existence possibly questionable;9 however, however, a fault may be of a North Shore fault is questionable present south south of of Isle Isle St. st. Ignace. Ignace. present Western Lake Superior appears to be underlain by by aa syncline, syncline, bounded on the north and south south by major fault systems, systems, which continues continues southeasterly into into the the eastern eastern half half of of Lake Lake Superior. Superior. southeasterly 36 36 �GEOLOGICAL GEOLOGICAL ANALYSIS AND AND REMEDIAL REMEDIAL ACTION ACTION IN AN AN OPEN OPEN PIT PITROCK ROCK SLIDE SLIDE D. H. H. Yard.ley Yardley D. School of of Mineral Mineral and and Metallurgical Metallurgical Engineering9 Engineering, School University of ofMinnesota, Minnesota, Minneapolis Minneapolis Tworock rockslides slides in the wall of an Two thesame same 't<Tall an open open pit pitininiron—formation iron-formation were studied to to determine determinethe thecause causeofofthe the slope slope failures, failures, and were studied and to propose remedialmeasures measurestotoprevent preventfurther further failures. failures. propose remedial The upperslide slide zone zone is is about The upper about 200 200 feet higher higher in in elevation elevationarid and LOO feet feet west of the lower one. one. 400 Although the the immediate immediate cause cause of of Although the the rock rock failures failures was was mining mining activity, activity, the the real real cause cause of of the the instabilinstability is the the presence of geologic structural structural defects. defects. is o SE. A iron—formationstrikes strikes N.35°E. The iron-formation N.J5°E. and and dips l2 system of of 12°SE. A system near—vertical joints near-vertical joints cuts the strata; strata; the most prominent set set strikes strikes A 50- to N.145°W,, N.45°W., parallel to the pit wall and and to to the the ore-trough. ore-trough. A o 100-foot thick fault zone that strikes N.5O°E. and dips 25—3O°SE lOO-foot strikes N.50 E. 25-JO oSE crosses the upper slide slide area area and and the the top top of of the the lower lower one. one. the upper upper slide slide is is aa J-foot 3—foot chloritic chioritic "green 'green shale shale The base of the layer. and permeable permeable to to water, the material material is is layer. iNhere Where it is fraculred fractured and water, the physically weak weak and and tends tends to to ttsqueeze "squeeze out.,J is stratistratiphysically out. This layer is graphically above above the the lower lower slide slide area. area. The chronology chronology of of the the slope slope failures and check check surveys surveys also also support support the the conclusion conclusion that that the the two two failures and slides are are not not expressions expressions of a single deep-seated cause cause and and thus thus slides single deep-seated could be treated treated independently. independently. j Remedial action action for for the the lower lower unstable unstable zone zone consisted consisted of of changing changing Remedial the sequence so so as to to decrease the the ratio ratio of of weight to to potential the mining sequence failure failure plane plane area. area. The upper slide slide area constituted an an unusual problem problem because economic considerations required haulage over rock-fill and over the economic unstable zone zone where all the elements creating instability instability still still The remedial the slide rock and exLsted. existed. The remedial design involved removal removal of the installation of post-tensioned post-tensioned cables cables in in rock rock back—fill. back-fill. The system system il is designed designed to to provide provide lateral lateral restraint restraint to to the the 'squeezing' 'I squeezing layer, layer, is increased frictional frictional resistance resistance at at the the back-fill back-fill bench bench interface, interface, and increased shear shear resistance within the back-fill by placing it in compression. This is believed to be the first designed use of postcompression. tensioned rock—fill rock-fill for for control control of of aa potential potential slide slide zone. zone. 37 37 � https://digitalcollections.lakeheadu.ca/files/original/5c09d2e9390894b4e68e13c6d3cb7f62.pdf 0bdef7544f3da876e9226dffa2551051 PDF Text Text FID TRIP GUIDE ST. CLOUD GRANITE DISTRICT CENTRAL MINNESOTA by R. K. Hogberg Minnesota Geological Survey University of Minnesota prepared for 11th ANNIJIiL INSTITUTE ON LANE SUPPRIOR GEOLOGY St. Paul, Minnesota, May 8, 1965 conducted by The Twin City Geologists �CONTENTS Page Introduction. . . Production ...... •••••••• •••a•••S5 2 ,.................. .•... •.•.....a• 2 •••••• •• a history. • . . , • , • • a Research by the General 3 a..••aa•aea•a 3 a•aaaaaaa•a•aaa•aaaaaaaaa a•aaaa•aaaaaaaaa••a 6 aaaaa 7 . . a i . a a •i• a a a a a a a a a a a a a •. a . a a 8 .....,.... 8 St. Cloud Gray Granodiorite. . a • a a a a • a as a. a a a a $ • • a. a a.. e.• a a as.. a 9 St. 9 geology. . . a a a • . a a • a . a a a • a • a • Rocklle C rysta].. quarry. . .. . a • a gray quarry. a a a a a a a a a a a a aaoaaa••aaaaaaa•aa •aaaaaa Shiely—Petters aggregate quarry. . • . • . •aaa•a.aaaaa aaaaaaaa• Introduction. • a • a a • a • a a • a a a a a . • a a a a a a a a a a • a a a • • • • • • • Cloud Red Granite. • • • • • as a a • a a a a a a a a a a • a aa • • a Quartz latite porphyry. •. . . . a • • ..•aa a . .aaaaaaaa•a a .' a a a a a a a a . • . a a a a • • a a . . a • a 10 Basalt and granite References cited. . .. a 10 a a a • a a •a a •a•. 12 aaaaaaaaaaaaaaaaaaaaaa 1 aa•aaaaaa•.aaaaa..••aaaaa• •a$• ILLUSTRATIONS Route of field trip, a • a. a a a a a a a a a a a a a a a a • a . a a a • Figure 1—-Generalized geologic section St. Cloud district.55555..... ii �ROCKVILLE ROUTE OF FIELD TRIP (Modified from Minnesota Highway Dept. Map) Scale ]:lLlóO �INTRODUCTION The purpose of this field trip is primarily to see the quarrying and processing operations of granite dimension stone in the St. Cloud district of central Minnesota. The Cold Spring Company will host the tour of their plant at Cold Spring. Leaders for the field trip will be I H. Yardley and R. K. Hogberg. Production History Quarrying began in the St. Cloud district in 1868, near the site of the present town of Sauk Rapids. The first salable products were rough From the late l880s until the late dimension stones and paving blocks. l92Os the sale of dimension stone rose steadily and reached a peak of $4,281,700 annually in 192:3. The major demand was for dimension stones obtained from St. Cloud Red, St. Cloud Gray, and Rockville granites.' From 1929 until the end of World War II sales were depressed and reached a low of $396,800 in 1943. The processing plants for dimension stone have decreased in number and increased in size since the early 190QU5 At present (1965) there are about 20 small granite processing plants, whereas in 1915 a record of 89 finishing plants were operated in Minnesota. However, due to consolidations and increased automation three of the plants-—two of which are located in the St. Cloud district——account for nearly all of the sales. One of the largest such plants in the world——that of the Cold Spring Granite Company—is our first stop. The 'hard' dimension stone industry of Minnesota has centered in the St. Cloud district. Those commercial quarries outside of the district—— in the Minnesota River valley and near Lake MUle Lacs—-are operated by St. Cloud—] ased firms. 2 �Sales of granite in the State in the decade 1952-1962 averaged The Rockville and the St. Cloud Gray "granites" about $3,327,000 annually. constitute most of the present sales from the St. Cloud district. Research by the Industry In recent years research by the industry has been largely confined The results have been quite success- to the field of product development. ful, have and resulted in the development of many new uses of dimension "granites in building construction. Among the new uses are: (1) precast monolithic wall units composed of a regular mosaic of 'granite blocks or, 'granit&' chips, in random arrangement, both set in a cement base; (2) floor tiles or patio-type pavements composed of granitic slabs with split or broken joints; "tumble stone," and built-up veneer (3) walls of split face ashlar or (4) various types of window unit facings composed veneer. granite Granite facings, the bread and butter of the industry, are specified in larger and thinner units than previously; as quarry of now result, the a blocks must be extremely large and free of fractures. GENERAL GEOLOGY The available geologic data on the St. Cloud district obtained by Margaret Skillman Woyski in 1945 and 1946. in a Ph.D. dissertation in 1946 and the largely Her work resulted a published paper in the Bulletin of the Geological Society of America in 1949. (Minn. was In 1961, Goldich and others Geol. Survey Bull. 41) published K/Ar and Rb/Sr ages on rocks of district and reviewed the current state of knowledge of the geology of the region. As a result of expansion of old quarries and opening of new quarries—- especially the Shiely—Petters "aggregate" quarry——excellent exposures are now available to observe the geologic relationships of the district. 3 �The commercial rock t,pes of the district have been given informal names such as St. Cloud Red, St. Cloud Gray9 Rockville, etc. These names have been used in the published literature (Woyski, l9149; Goldich and In addition, each of the others, 1961) and are now well established. companies has assigned many trade names to the dimension stones they sell. Figure 1 Generalized Geologic Section - (millions of years) 0.01 to 0.035 Quaternary Cenozoic Character and Distribution Age System and Period Era St. Cloud District Stratified drift; sandy and clayey till ——unconforrnity— 90 Upper Mesozoic Cretaceous Small vpockets of sandy, clayey, shaly and less commonly lignitic sedi— ments I i—unconformity— (basalt and granite porphyry dikes) Penokean Middle I Intrusive Rocks Precambrian l,62l'0 Younger granites (St. Cloud Red, Rockville, Crystal Gray, and quartz latite dikes) I 1,780 Older granodiorite and related rocks (St. Cloud Gray Granodio rite) —-unconformity— Thomson Formation (slate, graywacke and schist) Inim±kie Group The rocks that have been quarried for dimension stone in the St. Cloud district are igneous rocks of intermediate and felsic composition that are Penokean (post—Animikian' in age (Goldich and others, 1961, p. 101—122). They intrude pelitic sedimentary rocks, now metamorphosed to medium—grade schists, and apparently were emplaced subsequent to the peak of deformation in the Penokean orogeny. The intrusive rocks distinguished by Woyski (19249) 4 �can be grouped according to age relations observed in the field into three classes: and (3) (1) basalt older granodiorite and related rocks, (2) younger granites, and granite porphyry dikes. Within the district, the older intrusive rocks are represented by the St. Cloud Gray Granodiorite. This rock underlies a roughly circular area at least three miles in diameter that lies south of St. Cloud. The rock has been dated by the K/Ar method at 1.78 b.y. (Goldich and others, 1961, p. 104). The younger granites comprise several types of intrusive rocks of intermediate to felsic composition. The major facies that were distinguished by Woyski (1949) are the St. Cloud Red Granite, Rockville Porphyritic Granite, and quartz latite porphyry. The St. Cloud Red Granite is a coarse-grained augite—hornblende granite. The Rockville Porphyritic Granite is a fine— to medium—grained microcline-quartz monzonite. The quartz latite porphyry has phenocrysts of hornblende and plagioclase in a felsitic groundmassQ All the rocks of this group are altered to some degree by late-stage deuteric and hydrothermal solutions. The sequence of alteration as recognized by Skillman (1946) was albitization, formation of chlorite—epidote—calcite, arid silicification. The late intrusive rocks include basaltic dikes and granite porphyry dikes that dominantly occupy N. 50° E.-trending fractures in the older rocks. Preliminary results on K/Ar dating of hornblende (G. N. Hanson, oral communication, 1965) from a basaltic dike from the Diamond Pink quarry, three and one—half miles southeast of St. Cloud, indicate that the dikes are somewhat younger than the Penokean rocks dated by Goldich and others (1961) but older than Keweenawan. The St. Cloud district was a positive area from late Middle Precambrian to late Cretaceous time. In the early Cretaceous(?) 5 (Sloan, 1964) a thick �kaolinitic regolith was developed on the bedrock surface. Reworking of the regolith by the late Cretaceous sea resulted in the relatively thin succession of sandy, clayey and shaly sediments found in isolated pockets throughout the district. Pleistocene drift consisting of sandy and clayey till and stratified silts, sands, and gravels mantles the irregular Precanthrian rock surface. The greatest thickness of drift known in the district is a north-trending sandy moraine that crosses highway 213 between Rockville and Cold Spring. Quarries in the older granodiorite and younger granites are located in a swampy area within and south of St. Cloud, where highs'' on the undulating Middle Precambrian bedrock surface form low knobby outcrops and lows are filled by a thin mantle of glacial outwash materials. of younger granites that protrude from the glacial outwash sands Outcrops and gravels in the valley of the Sauk River and its tributaries are the sites of several other quarries. ROCKVILLE QIL4RRY Cold Spring Granite Company The Rockville quarry, within the Rockvifle Porphyritic Granite, has been the largest producer of dimension stone in Minnesota for many years. The relatively wide spacings of the joints and the general consistency of color, grain-size, and texture enable the operators to meet the demand for quarry blocks of consistent quality. The shape and limits of the quarry are governed by two steeply-dipping intersecting N. 550 across spacing 350/4,50 W. and The spacing between fractures ranges from 25 to 55 feet. E. N. 50_100 fracture sets, which strike respectively N. E.-trending fracture that dips the quarry. A 600_700 A NW cuts diagonally sheeting that dips gently to the southwest has a that ranges from 5 feet near the top to 30 feet near the bottom of the quarry. 6 �The quarry is located within a belt of outcrops of the Rockville that extends from St. Cloud southwestward to Richmond. The Rockville crosscuts the St. Cloud Gray Granodiorite and has irregular contact with the St. Cloud Red Granite to the north and east of the quarry. Inclusions of schistose material are quite abundant in the Rockville within the upper part of the quarry. The Rockville is a pink to reddish—gray porphyritic microcline quartz The potassic feldspar is pert.hitic and forms large crystals monzonite. The groundmass is fine— to medium-grained and is 1-6 cm. in length. composed of about equal quantities of gray quartz and white plagioclase (andesine-oligoclase) and contains about 10 percent biotite. Easily recognized accessory minerals are hornblende, plagioclase and magnetite. Myrmekitic quartz, replacement rims of early plagioclase, and some pyrite- bearing epidote veinlets are thought to represent late stage deuteric and hydrothermal late— stage activity. Aplite dikelets commonly less than 5 cm. wide fill fractures. CRYSTAL GRAY GRANITE QUARRY Cold Spring Granite Company The Crystal Gray quarry, which is 100-150 feet east of the Sauk River, was opened about 25 years ago by the Pyramid Quarry Company. It was purchased about 10 years ago by the Cold Spring Company who has operated it since that time. The quarry was completely flooded by overflow of the Sauk River in early April, 1965. The quarry is bounded on the north and south by vertical fractures that strike N. )45 ). and on the east and west by vertical fractures that strike N. 45° . A fracture set that strikes N. NE., and a five-foot basalt dike that strikes N. cross the quarry diagonally. 80° W. and and dips 80° 60° E. and dips 80° NW., The fractures have a 5- 7 to 30—foot separation. �The sheeting fractures have approximately a 5-foot separation in the upper part and a greater separation in the lower part of the quarry. A prominent sheeting fracture which is 20-35 feet below the quarry rim strikes N. W. 40 and dips 100_iSo SW. towards the Sauk River. The Crystal Gray is a porphyritic quartz monzonite that has somewhat smaller phenocrysts than the Rockville. It is a distinctively purplish to greenish-gray facies of the younger granites and quarry. average is known only at this The pinkish-gray potassic feldspar phenocrysts are perthitic and 10 mm. in length. The medium—grained groundmass consists of approximately 30 percent opalescent quartz, 30 percent greenish-gray plagioclase (andesine to oligoclase), and 10 percent biotite. accessory minerals are magnetite, plagioclase, and The hornblende. Crystal Gray appears to have had a crystallization history similar to the Rockville. to Observable Skiliman (1946) suggests that the gray coloring is due the almost complete assimulation of xenoliths of St. Cloud Gray Granodiorite. Alteration is strong along fractures in the rock, and is indicated by the presence of pyrite, chlorite, and reddish feldspars. On the west side of the quarry, bedrock is overlain by 5—10 feet of stratified glacial drift. On the east side the bedrock capping consists of about J feet of kaolinite-rich regolith, about 10 feet of Cretaceous sandy shale and clay, and a 3— 5-foot layer of sand and gravel. SHIY-PETTERS AGGREGATE QUARRY Introduction The Shiely—Petters quarry was opened in 19499 after the operating company abandoned an attempt to use nearby waste rock, from former quarry operations, for production of aggregate. from Approximately half the production the plant is sold for railroad ballast; the remainder is shipped to markets that require high—grade aggregate. 8 The quarry is approximately 850 �9 50 about of consists and granite, augite—hornblende red to pink grained coarse— a is It quarry. the of wall west the in Gray Cloud St. the in and wall north the along monzonite quartz microcline with associated stringers dike-like and masses irregular small as seen be can Red Cloud St. The Granite Red Cloud St. Gray. Cloud St. the in veinlets surround that halos alteration greenish-black mottled to red to pink in resulted granites, younger the from emanated which alteration, hydrothermal stage late A 1946). (Skiliman, granites younger the by metasomation of degree the reflect to thought is rock the in feldspar potassic and quartz of quantity chalcopyrite. and pyrite, magnetite—illmenite, are minerals accessory The identifiable Easily feldspar. potassic pink percent 10 arid quartz, gray or blue percent 15 augite, and hornblende percent 15 oligoclase), (andesine- plagioclase bluish-gray percent 50 granodiorite, hornblende augite fine—grained to The inclusions. biotite-rich approdmately of consisting medium- a is rock unaltered and hornblende black to gray dark abundant quarry. contains and altered, somewhat pinkish-gray, is it Commonly the of ends west and east the in exposed is Gray Cloud St. The Granodiorite Gray Cloud St. quarry. the of part lower the in feet 25 about to increases spacing the surface; the near feet five about of intervals at spaced is sheeting The NE. 70° dips and W. 800 N. strike fractures sheeting respectively, east and north, northwest9 trend that sets fracture steeply-dipping three stops. previous the at examined quarries the in those to addition In to contrast in fractured, intensely are quarry the within rocks The deep. feet 140—60 is it direction; north-south a in wide feet 300—450 and direction east—west an in long feet �percent perthitic potassic feldspar9 30 percent quartz9 10 percent white plagioclase (andesine—oligoclase), and 10 percent biotite. Easily identifiable accessory minerals are hornblende, magnetite, and hematite. The crystallization history probably was similar to that of other fades of the younger granites. Skiliman (1946) suggests that the St. Cloud Red differs from the other younger granites mainly in having incorporated substantial quantities of the earlier-crystallized St. Cloud Gray Granodiorite. She attributes the pronouncedly red color to intense alteration by late-stage hydrothermal solutions. The sequence of hydrothermal alteration as recognized by Skillman (1946) was albitization, formation of chlorite-epidote—calcite, and silicification. The intense albitization of potassic feldspars released iron as hematite. A less intense alteration marked by chlorite-epidote-calcite is shown by irregularly colored green rocks that are adjacent to closely spaced fractures. Quartz Latite Porphyry Quartz latite porphyry is exposed as massive rock units in the north wall of the quarry. is Skiliman (1946, p. 81) says the quartz latite porphyry later than the St. Cloud Gray and St. Cloud Red. Phenocrysts of hornblende and bluish—gray plagioclase occur in a dark pink felsitic groundmass. Potassic feldspar and quartz in the rocks are thought to have been introduced by late—stage deuteric solutions. Basalt and Granite Porphyry Dikes The late intrusive rocks exposed in the quarry consist of basaltic dikes and granite porphyry; minor pegmatite, quartz veins, and chloriteepidote—calcite veinlets cut the rocks. The basaltic dikes range in width from 1 to 50 feet and average about 5 feet. They occupy three joint sets: 10 (1) N. 35°—50° W., 70°—80° NE., �a in set are 11 s. groundmas granulitic and these, of some of aggregates and hornblende, biotite, oligoclase, quartz, feldspar, potassic perthitic of consist phenocrysts The fractures. post-basalt the fill dikelets porphyry granite narrow Very andesine). (zoned plagioclase and olivine, and uralite augite, of mixtures various of consist cores the plagioclase; and magnetite, glass, basaltic of proportions equal approximately of composed margins chilled have They amphiboles. bluish-green and plagioclase sodic of amounts anomalous containing rock acidic more to basalt normal a from composition NE. trend and gypsum some contacts. 75o_900 E.9 50°—70° N. (3) W. The 35°_L()° N. hematite-stained are dikes massive; conjugate wall the to 600 joints jointing columnar horizontal rudimentary have NW. in vary dikes 70°_80° dip and contain that zones mylonitized are fractures Post-basalt and Most some and NW., 70°—90° E., loO_200 N. (2) �REFERENCES CITED Goldich, S. S., Nier, A. 0., Baadsgaard, H., Hoffman, J. H, and Krueger, H. W., 1961, The Precambrian geology and geochronology of Minnesota: Minn. Geol. Survey Bull. 41, l93 p. Skiliman, Margaret W., 1946, Intrusives of central Minnesota: Unpublished Ph.D. Thesis, Univ. of Minnesota, 211 p. Sloan, R. E., 1964, The Cretaceous System in Minnesota: Minn Geol. Survey Rept. mv. 5, 64 p. Woyski, Margaret S., 1949, Intrusives of central Minnesota: America Bull., v. 60, no. 6, p. 12 999—1016. Geol. Soc. � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Institute on Lake Superior Geology: Proceedings, 1965 Description An account of the resource Institute on Lake Superior Geology. University of Minnesota, St. Paul, Minnesota. May 6-8, 1965. Creator An entity primarily responsible for making the resource Institute on Lake Superior Geology Date A point or period of time associated with an event in the lifecycle of the resource 1965 Contributor An entity responsible for making contributions to the resource R.L. Bleifuss Bill Bonnichsen Peter J. Clarke Joseph P. Dobell Robert W. Leonardson Charles Fairhurst Bevan M. French Crawford E. Fritts John C. Green Tsu-Ming Han James W. Villar Glen R. Himmelberg Gilbert N. Hanson J.D. Juilland Gene L. LaBerge Henry Lepp Geoffrey W. Mathews Howard J. Meyer William J. Hinze G.B. Morey Richard W. Ojakangas Dennis P. Rebello George M. Schwartz Kenneth Segerstrom Kiril Spiroff F.M. Swain Mykola Malinowsky David Nelson Walter S. White Robert J. Willard Richard J. Wold D.H. Yardley Format The file format, physical medium, or dimensions of the resource PDF Language A language of the resource English