Mineral resource assessment of the Iron River 1° x 2° quadrangle, Michigan and Wisconsin
The Iron River 1? x 2? quadrangle contains identified resources of copper and iron. Copper-rich shale beds in the north part of the quadrangle contain 12.2…
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GEOLOGICAL SURVEY CIRCULAR 887 Mineral Resource Assessment of the Iron River 1 ° X 2° Quadrangle, Michigan and Wisconsin Prepared in cooperation with Geological Survey Division, Michigan Department of Natural Resources, and Wisconsin Geological and Natural History Survey
Mineral Resource Assessment of the Iron River 1 ° X 2° Quadrangle, Michigan and Wisconsin By W. F. Cannon GEOLOGICAL SURVEY CIRCULAR 887 Prepared in cooperation with Geological Survey Division, Michigan Department of Natural Resources, and Wisconsin Geological and Natural History Survey An assessment of the mineral resources and of areas judged to have varying degrees of favorability for undiscovered mineral deposits in the Iron River 1° X 2° quadrangle
United States Department of the Interior JAMES G. WATT, Secretary Geological Survey Dallas L. Peck, Director Library off Congress Cataloging in Publication Data Cannon, William F. Mineral resource assessment of the Iron River 1° X 2° quadrangle, Michigan and Wisconsin. (Geological Survey circular ; 887) Bibliography: p. Supt. of Docs, no.: I 19.4/2:887 1. Mines and mineral resources Michigan. 2. Mines and mineral resources Wisconsin. I. Michigan. Geological Survey Division. II. Wisconsin Geological and Natural History Survey. III. Title. IV. Series. QE75.C5 no. 887 557.3s [553'.09774'975] 83-600055 [TN24.M5]
Free on application to Distribution Branch, Text Products Section, U. S. Geological Survey, 604 South Pickett Street, Alexandria, MA 22304
CONTENTS /Lrltiiv wivugiiiviii'd
The Iron River CUSMAP Project Surficial geologic map Structural and tectonic map RrtiicnifM" ffrsivitv m$m Aeromagnetic map Metamorphic map Identified resources Reserves Hypothetical resources Speculative resources Assessment of identified resources Assessment of undiscovered resources Classification of resources in the Iron River quadrangle - Identified resources Page
Classification of resources in the Iron River quadrangle Continued Undiscovered resources Unfavorable areas Mineral resources of the Iron River quadrangle Identified resources Copper Iron Hypothetical resources Copper Iron Volcanogenic massive sulfide deposits Shale and iron-formation hosted deposits Deposits associated with mafic intrusive rocks Silver-bearing shale Diamond Conclusions Bibliography Page ILLUSTRATIONS FIGURE 1. Classification of resource categories 2. Generalized mineral resource map of the Iron River 1° x 2° quadrangle Page TABLES TABLE 1. Mineral resources of the Iron River 1 ° x 2° quadrangle HI
Mineral Resource Assessment of the Iron River 1° X 2° Quadrangle, Michigan and Wisconsin By W. F. Cannon ABSTRACT The Iron River 1° x 2° quadrangle contains identified resources of copper and iron. Copper-rich shale beds in the north part of the quadrangle contain 12.2 billion pounds (5.5 billion kilograms) of copper in well-studied deposits including 9.2 billion pounds (4.2 billion kilograms) that are economically minable by 1980 standards. At least several billion pounds of copper probably exist in other parts of the same shale beds, but not enough data are available to measure the amount. A small amount, about 250 million pounds (113 million kilograms), of native copper is known to remain in one abandoned mine, and additional but unknown amounts remain in other abandoned mines. About 13.25 billion tons (12.02 billion metric tons) of banded iron-formation averaging roughly 30 percent iron are known within 500 feet (152.4 meters) of the surface in the Gogebic, Marquette, and Iron River-Crystal Falls districts. A small percentage of that might someday be minable as taconite, but none is now believed to be economic. Some higher grade iron concentrations exist in the same iron-formations. Such material was the basis of former mining of iron in the region, but a poor market for such ore and depletion of many deposits have led to the decline of iron mining in the quadrangle. Iron mines of the quadrangle were not being worked in Many parts of the quadrangle contain belts of favorable host rocks for mineral deposits. Although deposits are not known in these belts, undiscovered deposits of copper, zinc, lead, silver, uranium, phosphate, nickel, chromium, platinum, gold, and diamonds could exist. INTRODUCTION The Iron River 1° x 2° quadrangle is bounded by lats 46° and 47° N. and longs 88° and 90° W. and includes several major mining districts that have produced large amounts of copper and iron. At present, only the White Pine mine, where copper is recovered from an extensive unit of copper-rich shale, remains active. In the past, a large number of mines, which are now abandoned, produced native copper. Parts of three major iron-mining districts the Marquette Range, the Gogebic Range, and the Iron River- Crystal Falls district are in the quadrangle. All have produced large amounts of iron ore but are now inactive. (Mining is still being done in the Marquette Range east of the Iron River quadrangle.) Large quantities of mineralized rock remain in the ground, mostly in subeconomic form, but changes in price, mining and processing technology, or demand could revitalize mining. In addition, many parts of the quadrangle are judged to be favorable ground for undiscovered mineral deposits. Much exploration by the mining industry was carried out during the 1970's, and a high level of exploration activity is likely to continue into the 1980's. Such exploration could expectably lead to the discovery of additional deposits or districts. Although present mineral production is relatively small, about 150 million pounds (68 million kilograms) or less of copper per year, the potential for future mineral production is great. The mineral potential of the quadrangle should enter into economic and land-use planning for the region and into considerations of future mineral supplies for the United States. This report summarizes a mineral resource appraisal of the quadrangle carried out between 1977 and 1980 by a team of geoscientists from the U.S. Geological Survey (USGS) as part of the Conterminous United States Mineral Assessment Program (CUSMAP). During that period, much new information was gathered, and older data were compiled and evaluated. All data were then considered to estimate the known mineral resources of the quadrangle and the potential for the existence of undiscovered resources.
The report summarizes the subactivities within the project, discusses the philosophy and techniques of resource assessment, and summarizes findings and conclusions about the mineral resources of the quadrangle. More detailed technical information is presented in the Iron River CUSMAP folio (USGS Maps I-1360-A to N). ACKNOWLEDGMENTS This resource assessment was made possible by the acquisition of a wealth of data and by the contributions from the Iron River project participants. These contributors are Henry Alminas, Maurice Brock, David Frishman, J. A. Kalliokoski, Elizabeth King, John Klasner, Richard Ojakangas, Warren Peterson, Bruce Smith, and Karen Wier. Anita Fenichel assisted in compiling much of the data and in drafting maps. Most of the annotated bibliographic entries were compiled by Alice Weis and Martina Johnson. THE IRON RIVER CUSMAP PROJECT Between 1977 and 1980, a team of geoscientists from the USGS constructed the detailed data base from which the mineral resource assessment of the Iron River quadrangle has been made. This team of experts in a number of scientific fields has made possible the acquisition and evaluation of a wide variety of data. A folio of maps presents this information in technical detail. Each component of the project is described briefly below. MINERAL RESOURCE MAP Map I-1360-A (Cannon, 1983a) shows the distribution of identified resources and areas of potential for undiscovered resources, The resource map was constructed by compiling information on known mineral deposits and by interpreting geologic, geochemical, and geophysical data to predict areas where resources are likely to occur. BEDROCK GEOLOGIC MAP The bedrock geology of the quadrangle is presented in map I-1360-B (Cannon, 1983b). The map was made largely from data gathered during detailed mapping by many geologists during the past 40 years. Two years were devoted to mapping areas that had not been mapped previously and to resolving the structure and correlation of some rock units. Interpretation of geophysical data also played a major role in understanding the bedrock geology in many parts of the quadrangle that are covered by sand, gravel, and other surficial deposits. SURFICIAL GEOLOGIC MAP The distribution of various types of unconsolidated deposits, mostly glacial deposits, is presented in map I-1360-C (Peterson, 1983). At the start of the project, little information was available on a regional scale, therefore, 3 years of field studies combined with an analysis of landforms as revealed by aerial photographs and topographic maps were needed to produce an adequately detailed map. The surficial geologic map is of great use in determining whether geochemical data and some types of geophysical data are related to surficial deposits only or possibly are caused by mineralization in underlying bedrock. STRUCTURAL AND TECTONIC MAP Additional information on the bedrock of the quadrangle is given in map I-1360-D (Cannon, 1983c). The structural and tectonic map provides information on the age, mode of origin, and subsequent history of rock units. Such information is useful in predicting rock units in which mineral deposits might have formed. As with the bedrock geologic map, much information was compiled from previous studies, but some new information was gathered during the CUSMAP study. BOUGUER GRAVITY MAP Map I-1360-E (Klasner and Jones, 1983) shows variations in Bouguer gravity values, identifies gravity anomalies, and includes interpretations of many of them. The CUSMAP project involved compiling data from previous surveys and performing additional surveys to provide a uniform coverage of the quadrangle and to adjust various older surveys to ,a common base value. The gravity map is useful in recognizing and tracing some broad tectonic features, in providing information on the density of rocks in the
subsurface, and in placing constraints on estimates of the depth of geologic features. AEROMAGNETIC MAP A map showing variations in magnetic attraction in the quadrangle (map I-1360-F) was compiled by King (1983). Data were from previous airborne surveys by the USGS in Michigan (Zietz and Kirby, 1971) and from John Karl of the University of Wisconsin at Oshkosh for Wisconsin. The Wisconsin data were compiled and published by Zietz and others (1977). For the current map, the Wisconsin data were recontoured by computer to add detail not shown in previous maps and were adjusted to match the Michigan data. Aeromagnetic data are invaluable in the Iron River quadrangle because they enable the tracing of numerous iron-rich magnetic units through areas where bedrock is not exposed and are an important source of information in making geologic maps. In addition, magnetic data can directly indicate some resources, such as iron-formations of possible economic value. METAMORPHIC MAP A map showing zones of metarnorphic intensity of various ages was published as map I-1360-G (Wier, 1983). Information was obtained by previous studies and by the microscopic examination of many new rock samples to determine their mineralogic makeup. The metarnorphic pattern is believed to control the distribution of some types of ore deposits, and the refinements and detail added by this study to the understanding of the metarnorphic pattern of the quadrangle have resulted in the definition of some belts of resource potential. GEOCHEMICAL MAPS Maps I-1360-H to N (Alminas and others, 1983a, b, c; Hoffman and others, 1983a, b; Hopkins and others, 1983a, b) present the results of an extensive survey of the trace-element content of soils. A total of 3,156 B-horizon soil samples (about 1 sample per 2 mi2) were collected and analyzed spectrographicaUy. The distribution and amounts of several important metals are shown on the maps along with interpretations of the distribution patterns of these elements. The variations of metal content in the soils reflect both regional trends in bedrock composition and more local variations, possibly related to mineralized areas in the underlying bedrock. An interpretation of the geochemical data has led to the identification of several areas where undiscovered mineral deposits might exist. ELECTROMAGNETIC STUDIES Airborne electromagnetic surveys were performed in parts of the quadrangle where such data are essential to a mineral resource appraisal. Results have been published in USGS Open-File Report 80-297 (Heran and Smith, 1980). Electromagnetic surveys identify units of rock that are electrically conductive. Information from the surveys is useful for mapping such conductive units in areas where bedrock is not exposed and also for more directly indicating the presence of some types of mineral deposits that are electrically conductive. URANIUM RESOURCE STUDIES Uranium resources were not a direct concern of the CUSMAP program. Concurrent studies were carried out, however, by Maurice Brock, J. A. Kalliokoski, Richard Ojakangas, and David Frishman of the USGS, funded in part by the National Uranium Resource Evaluation program of the Department of Energy. Information and advice provided by these geologists have been incorporated into the overall resource evaluation of the Iron River quadrangle. MINERAL RESOURCE TERMINOLOGY Mineral resources are naturally occurring concentrations of materials that are useful to man and that can be economically extracted now or potentially in the future. Resources, in their broadest sense, include all such existing concentrations, whether or not they have yet been discovered. Mineral resources can be broadly classified, therefore, into identified resources (those that have been discovered) and undiscovered resources (those that reasonably may exist but that have not yet been found). Identified resources are further subdivided into reserves (material that is presently profitable to mine) and subeconomic resources (material that requires either some increase in price or
improved mining or processing technology to become economically minable). Undiscovered resources are subdivided into hypothetical resources (material yet to be found in known mining or mineralized districts) and speculative resources (deposits in yet unrecognized districts or yet unrecognized types of deposits). The classification of mineral resources is discussed in detail in USGS Circular 831 (U.S. Bureau of Mines and U.S. Geological Survey, 1980). A simplified version of that classification system is used here (fig. 1), and the definition of categories as they apply to the Iron River quadrangle is given below. IDENTIFIED RESOURCES Identified resources are concentrations of elements known to exist in specific locations. Information on their existence and nature is derived from direct observations of mineralized rock at the Earth's surface, in drill holes, or in mine workings. In general, enough information exists to make at least semiquantitative estimates of the tonnage and grade of mineralized rock. RESERVES A reserve is an identified resource that has been thoroughly measured and tested and that is known with reasonable certainty to be economically exploitable by current technology and under current economic conditions. The copper-rich shale at the White Pine orebody is the only material in the Iron River quadrangle classed as a reserve in this report. SUBECONOMIC RESOURCES A subeconomic resource is that portion of identified resources that is not economically exploitable at present. Future increases in price or cost savings from improved mining or processing technology may convert subeconomic material to the reserve category. HYPOTHETICAL RESOURCES Hypothetical resources are concentrations of elements that can reasonably be inferred to exist in known mining or mineralized districts or extensions of those districts but that have not yet been found. In the Iron River quadrangle, for instance, hypothetical resources include deposits of native copper that might exist but have not yet been discovered in or near the abandoned mining district near Greenland and Winona. Future exploration may find some of these deposits and convert them to the identified-resource category. SPECULATIVE RESOURCES Speculative resources are undiscovered concentrations of elements whose existence is believed possible on the basis of broad geologic reasoning but for which there is no direct indication of their existence. No deposits of the elements are known in the immediate vicinity. Exploration of belts deemed likely to contain speculative resources may discover deposits of such materials and thereby convert them to identified or hypothetical resources. In the Iron River quadrangle, speculative resources include massive sulfide deposits of copper, zinc, and lead that are not yet known to exist but that are considered possible because the geology of parts of the quadrangle is very similar to the geology of other areas that contain massive sulfide deposits. MINERAL RESOURCE ASSESSMENT TECHNIQUES Mineral resource assessment is the quantification and estimation of the amount and nature of potentially useful minerals and the identification of areas where resources exist or may exist. Assessment is based on data from many sources, including geologic mapping, geochemical and geophysical surveys, studies of oreforming processes, and the distribution patterns of ore deposits and their size and grade in well-explored mining districts. The objective of the Iron River CUSMAP project has been to assemble the best possible and the most up-to-date data base on which to make a resource assessment. Such data, however, are never complete and commonly are not totally diagnostic of the presence or lack of mineralization. Any resource appraisal is a state-of-the-art estimate and is subject to revision and revaluation as more data are obtained and as a better understanding of ore-forming geologic processes is achieved. The assessment presented here is based on our knowledge in 1980.
o u IU JBECONOIV W IDENTIFIED RESOURCES Reserves Subeconomic resources UNDISCOVERED RESOURCES Hypothetical resources Speculative resources Increasing degree of geologic assurance
FIGURE 1. Classification of resource categories as used in this report. Modified from U.S. Bureau of Mines and U.S. Geological Survey (1980). Judgment is an important factor, especially in estimating undiscovered resources, and somewhat different assessments probably would be made by different individuals using the same data. In short, a mineral resource assessment must be viewed as an estimate. The accuracy of the estimate reflects the quality and amount of data available and the degree of understanding of the geologic occurrence of ore deposits and the processes that formed them. Future exploration and research probably will provide new data and insights that will allow improved estimates to be made. In the Iron River quadrangle, identified resources include the copper-bearing shale in and around the White Pine orebody, native copper in and near the Greenland and Winona mining districts, and iron in banded iron-formation in the Gogebic, Marquette, and Iron River-Crystal Falls districts. All areas of identified resources either have had past mining or have been thoroughly tested by mining company drilling programs. Those companies generally have made much information available for use in evaluation of the resources. ASSESSMENT OF IDENTIFIED RESOURCES The assessment of identified resources is relatively straightforward. It is based on data directly indicating the tonnage, grade, and location of mineralized rock. Calculations and estimates of tonnage and grade can be made from available data, and the degree of certainty of the assessment commonly can be expressed in quantitative or qualitative terms. ASSESSMENT OF UNDISCOVERED RESOURCES The assessment of undiscovered resources is an estimation generally based on an analogy between the geologic setting of well-known deposits or districts throughout the world and the geologic setting of the area being assessed. As suggested and portrayed on the resource map that accompanies this report, undiscovered resources are probably restricted to certain belts or zones. Furthermore, only those zones at or
near enough to the Earth's surface in areas that contain deposits that are likely to be discovered are shown. Hence, zones having a potential for undiscovered resources might be viewed as areas where mineral exploration is most likely to occur and where discoveries might be made. As such, the assessment is a prediction of future events mineral exploration and possible discovery of deposits that might occur. As a prediction, it is subject to uncertainty and error but should be considered in planning. Mineral deposits can be grouped into genetic types by placing together all deposits that have formed as a result of similar processes, regardless of their location. For each type of deposit, a genetic model can be developed to describe the process or set of processes that operated in the geologic past to form the deposit. A set of features recognizable in rocks and deposits caused by those processes can be defined. Such processes commonly operated over an area larger than that within the ore deposit and therefore have recognizable features that provide a larger target for mineral exploration than the deposit itself. Recognition of the features indicative of ore-forming processes may lead to the supposition that an orebody could exist nearby, even though it may not be observable at the surface. Furthermore, ore-forming processes commonly take place in a broader geologic framework. For instance, processes that may form one genetic type of ore deposit may occur only in volcanic regions, whereas processes that form a second type may occur only along marine shorelines. The presence and recognition of rocks formed in such widespread environments provide a regional framework for resource assessment. As an example of how such reasoning leads to a resource assessment, let us examine a specific case. Massive sulfide deposits are ores of copper, zinc, lead, and various byproducts. Such ores are common in many parts of the world; thorough study of them on a worldwide basis reveals striking similarities in the way that they formed and in the types of rocks that commonly surround them. It is generally agreed that many massive sulfide deposits form on the sea floor when material crystallizes from fluids emitted by submarine hot springs in areas of volcanic activity. Such deposits commonly are interlayered with submarine volcanic and sedimentary rocks near ancient volcanic vents. The vent areas are recognized by characteristic textures preserved in the rocks. No massive sulfide deposits are known in the Iron River quadrangle, but some have recently been discovered as little as 20 miles (32 kilometers) south of the quadrangle. To determine if undiscovered massive sulfide deposits might exist in the Iron River quadrangle, one first looks for areas that contain submarine volcanic rocks because massive sulfides might have formed in the general environment where such rocks formed. Submarine volcanic rocks are found in several belts in the south half of the quadrangle, and these belts are judged to have at least broad favorability for the occurrence of massive sulfides. Each volcanic belt is then examined in more detail to determine if areas within it can be identified as having been near volcanic vents. If such vent areas can be identified, their potential is considered to be even higher than that of the volcanic belts in general, because rocks within these areas have formed not only in a generally favorable setting but also in the specific part of that setting where massive sulfides typically have formed elsewhere in the world. Within identified vent areas, further examination might reveal features directly indicative of ore-forming processes, or geochemical or geophysical measurements may suggest that ore is buried beneath the surface. In some cases, mineralized rock might be directly observed, but such is not likely to be the case in the Iron River quadrangle because most bedrock is covered by a veneer of glacially transported sand and gravel. By using such evidence and reasoning, various parts of the quadrangle can be classified as being broadly favorable for mineral occurrence (class C areas of this report). Parts of some class C areas are given additional importance because rocks within them are known to have formed in specific environments where ore might have formed (class B areas). Parts of some class B areas are further identified as having experienced potentially ore-forming processes (class A areas). (See section on "Undiscovered Resources.") The ability to classify areas in this manner is limited by the amount of geologic information on the area and by the detail known and the assurance about the mode of origin of a genetic type of deposit. In many parts of the Iron River quadrangle, knowledge of the bedrock is not detailed because of the cover of sand and gravel. Hence, the information required to define class A and class B areas commonly is lacking, and most areas of undiscovered resources can be identified only as class C. Likewise, incomplete understanding of the mode of origin of some genetic types of deposits does not allow a definition of criteria specific enough to differentiate class A or class B areas from the general belts of class C favorability. As a result, many favorable belts in the Iron River quadrangle are classified only as class C. Within these belts, the lack of class A or class B zones in the present
assessment may reflect the lack of information more than the absence of mineralization. CLASSIFICATION OF RESOURCES IN THE IRON RIVER QUADRANGLE The Iron River quadrangle has been zoned into seven categories of resource potential, as shown in figure 2. UNFAVORABLE AREAS Unfavorable areas are those for which no strong indications of economic minerals occur either directly or by an analogy with known deposits elsewhere. Unfavorable areas contain types of rocks in which few, if any, important ore deposits occur anywhere in the world. No area, however, can be considered totally unfavorable. Additional knowledge, discovery of new classes of deposits, or future needs for minerals not currently in demand could cause areas now considered unfavorable to be reclassified eventually as favorable. IDENTIFIED RESOURCES Identified resources are known deposits whose location can be shown on a map and for which some information on size and grade exists. Three categories of identified resources are used in this report: 1. Reserves. Known concentrations of materials economically exploitable in 1980. 2. Outcrop belts of mineralized strata. Areas in which continuously or discontinuously mineralized rock is exposed or. exists in the shallow subsurface. 3. Subsurface mineralized rock. Areas in which mineralized rock is known to exist underground but is overlain by unmineralized rock. These areas are, in general, the subsurface extensions of outcrop belts of mineralized rocks. FAVORABLE AREAS Favorable areas are those where some indication, either direct or indirect, of undiscovered mineral deposits is known. Favorable areas are here subdivided into three categories. Class C areas are those areas for which geologic evidence indicates a general environmental setting where mineral deposits could occur, but no direct evidence of mineralization is known. Class B areas are those areas where the contained rocks represent the specific parts of the generally favorable environment where mineral deposits could have formed and, hence, have a higher favorability than class C areas. Class A areas, the most favorable areas, are areas where actual mineralizing processes are known to have occurred. Whether those processes formed ore anywhere is not necessarily known. UNDISCOVERED RESOURCES Undiscovered resources are deposits likely to exist but not yet discovered. They, of course, cannot be shown on a map. Rather, areas can be shown for which varying degrees of favorability for the discovery of such deposits can be inferred. The zones shown in figure 2 are belts in which potentially mineralized rock is at or very near the surface and in which contained deposits could be found by standard exploration techniques. Such potentially mineralized rocks generally extend into the subsurface away from their outcrop belts, but these subsurface extensions are not shown in figure 2. Although the rocks in the subsurface may be as likely to be mineralized as those at the surface, deposits that might exist at deep levels are not likely to be discovered in the near future. Areas are broadly classified as favorable and unfavorable. MINERAL RESOURCES OF THE IRON RIVER QUADRANGLE Figure 2 shows areas of the Iron River quadrangle where resources are known to exist or thought likely to exist, and table 1 summarizes the resources of the quadrangle. The resources are discussed separately in identified, hypothetical, and speculative categories. IDENTIFIED RESOURCES COPPER Zones Cui through Cus contain identified copper resources. Zone Cui is the area underlain by the reserves of the White Pine mine. The reserves, for the most part, are in the deep subsurface. The material
TABLE 1. Mineral resources of the Iron River I°x2° quadrangle Reserves Copper: White Pine orebody 9.2 billion pounds (4.2 billion kilograms) sulfide and native copper. Snbeconomic identified resources Copper: Presque Isle deposit 2.7 billion pounds (1.2 billion kilograms) native and sulfide copper. Caledonia mine 250 million pounds (113 million kilograms) native copper. Extensions of mineralized bed at White Pine Probably at least several billion pounds sulfide and native copper. Iron: Banded iron-formation within 500 feet (152.4 meters) of the surface containing an unknown percentage of potential taconite bodies. Marquette range 1.5 billion tons (1.4 billion tonnes) iron-formation. Gogebic range 10 billion tons (9 billion tonnes) iron-formation. Iron River-Crystal Falls 1.75 billion tons (1.59 billion tonnes) iron-formation. Hypothetical resources (not quantified) Copper: Native copper in extensions of Greenland and Winona districts. Iron: High-grade iron ore in Marquette, Gogebic, and Iron River-Crystal Falls districts. Speculative resources Copper, zinc, lead, silver, gold, platinum, chromium, nickel, cobalt, uranium, phosphate, and diamonds could possibly exist in many belts of favorable host rocks in the quadrangle. classified as reserves has an average grade of 1.2 percent copper, a cutoff grade of 1.0 percent copper, and a minimum mining height of the mineralized layer of 7.5 feet (2.3 meters). The deposit is a gently dipping layer of copper-rich shale extending from the surface to considerable depth, the deepest parts are toward the east. The deposit contains 360 million tons (327 million tonnes) of ore and about 9.2 billion pounds (4.2 billion kilograms) of copper. Copper is contained in both sulfide minerals and native copper. Small quantities of silver are also in the ore. Part of the silver is recovered as a separate product during refining. Zone Cu2 is the belt along which the copper-bearing shale is at or near the surface. Although it is generally mineralized, it is not economic because it has lower grade, is in thinner beds, or is more difficult to mine than the material that constitutes the White Pine reserve. Zone Cu3 consists of areas where the copper-rich shale is known from drilling to exist in the subsurface. None is now economic because of low grade, thin beds, or mining problems including great depth. An area peripheral to the White Pine reserve is probably close to being economic. The material in the Presque Isle deposit, including belts Cu2 and Cu3, is also close to being economic. The Presque Isle deposit is estimated to contain 95 million tons (86 million tonnes) of ore at an average grade of 1.27 percent copper, for a total of about 2.7 billion pounds (1.2 billion kilograms) of copper (Wilband, 1978). The remaining areas of Cu3 are conservatively estimated to contain at least several billion pounds of copper. Zone Cu4 contains volcanic rocks (basalt) that are mineralized with native copper. Many inactive mines are in the area. An unknown amount of mineralized rock of subeconomic grades is still in the ground at some mines, and additional mineralized rock may yet be found in the belt. At the Caledonia mine, about 11.5 million tons (10.4 million tonnes) of rock having an average grade of 1.1 percent copper is known to remain in the ground (Wilband, 1978). The discontinuously mineralized rock of Cu4 forms a thick slab inclined northward so that it continues in the subsurface north of the outcrop belt. Zone Cu5 is the extension of known mineralized rock at depth from Cu4 . Its northern limit is defined approximately by the limit of data from mine workings and drilling, but mineralization may extend downward and northward beyond the deepest data points. IRON Very large quantities of iron-rich rocks exist in the quadrangle. All those of potential resource importance are banded iron-formations. Production of ore between 1872 and 1978 totaled about 210 million tons (191 million tonnes), mostly from the Iron River- Crystal Falls district. All of that production was of relatively high grade ore (generally 50-60 percent iron), which occurred as irregular bodies within lower grade iron-formation having about 30 percent iron. Since the 1950's, the production of iron in the United States has shifted away from the use of natural highgrade ores to pelletized iron concentrates produced from iron-formations containing about 30 percent iron, commonly called taconite. As a consequence, the market for high-grade ores has greatly diminished, and exploration for new deposits has virtually ceased in the area. Although most of the iron-formation in the Iron River quadrangle does contain 30 percent iron or more, none now is commercially workable as taconite. Various problems, including thinness of ironformation layers, steep dips, and large amounts of waste rock above and interlayered with the taconite, make it difficult to mine profitably large tonnages of ore from open pits, as taconite must now be mined. In addition, the mineralogic complexity of much of the iron-formation makes most of it untreatable by current metallurgical concentrating processes. Zones Fd through Fe7 contain identified resources of iron. The iron-resource potential of these zones is shown in figure 2 and described briefly below.
Areas in which iron-formation exists in the subsurface are of little short-term resource importance. Although they could contain undiscovered deposits of high-grade ore, the present poor market for such ores make it unlikely that subsurface iron deposits will be explored for and found in the foreseeable future. Some of the material could be used as taconite but would not be commercially minable unless mining technology were improved so that underground mining became economically competitive with open-pit mining. Such areas could have some resource importance sometime in the 21st century if near-surface iron deposits now being exploited elsewhere become depleted and if improved mining and metallurgical technology permit their mining and processing. The two areas having the best potential for taconite are probably zones Fd and Fe2 in the western part of the Marquette Range. Both areas contain substantial amounts of iron-formation very similar to that now being mined at the Republic mine, which is only about 1 mile (1.6 kilometers) east of the quadrangle. Zone Fd is the outcrop belt of iron-formation in the western Marquette Range. Some high-grade ore has been produced in the past. Parts of the formation may be amenable to treatment as taconite. About 0.75 billion tons (0.68 billion tonnes) of iron-formation are within 500 feet (152.4 meters) of the surface. About 250,000 tons (227,000 tonnes) of that contain a mineralogic makeup that may be treatable by existing concentration processes. The deposits of the western Marquette Range are probably not economic now because of the thinness of iron-formation layers and the relatively large amounts of waste rock that would have to be moved to recover the iron-formation. Zone Fe2 is a second outcrop belt of iron-formation having some taconite potential in the western Marquette Range. The tonnages of available rocks are about the same as those for zone Fd, and development of the area faces the same problems. Zone Fe3 is the outcrop belt of iron-formation in the Gogebic Range. The area has had some past production of high-grade ore. Some high-grade ore may remain to be found. The area contains about 10 billion tons (9 billion tonnes) of iron-formation within 500 feet (152.4 meters) of the surface. Some of that material might be useful as taconite in the future if metallurgical improvements allow treatment of the mineralogically complex iron-formation. Zone Fe4 is the outcrop belt of iron-formation in the Iron River-Crystal Falls district. The area has had a large production, about 210 million tons (191 million tonnes), of high-grade ore. James and others (1968) estimated that about 50 million tons (45 million tonnes) of identified ore remain in the ground and that about 90 million tons (82 million tonnes) of undiscovered ore exist. About 1.75 billion tons (1.59 billion tonnes) of iron-formation are within 500 feet (152.4 meters) of the surface (James and others, 1968), but this material has very little taconite potential because of mining problems and unsuitable mineralogy. Zone Fes is the subsurface extension of the ironformation of the Gogebic Range projected to about a 1-mile (1.6-kilometer) depth. The iron-formation has some potential for high-grade ores and very limited short-term potential as taconite. Zone Fe6 is the subsurface extension of the ironformation of the Marquette Range to a depth of about 1 mile (1.6 kilometers). The iron-formation contains some potential resources of high-grade ore and, largely because of depth, has very small potential as a resource of taconite. Zone Fe7 is the subsurface extension of the ironformation of the Iron River-Crystal Falls district to a depth of about 1 mile (1.6 kilometers). The material probably contains undiscovered deposits of high-grade ore but has very limited taconite potential because of depth and unsuitable mineralogic form. HYPOTHETICAL RESOURCES Hypothetical resources are undiscovered deposits in known mineral districts, as shown in figure 2, that are restricted to parts of the native copper district and the iron-mining districts. COPPER Zone Cu6 in figure 2 is the extension along the geologic trend of the same rocks that are mineralized in belts Cu4 and Cu5, but only minor (subeconomic) mineralization is known. A high potential for undiscovered native copper and perhaps sulfide copper is indicated by strong similarities in nearly all details between these rocks and the mineralized rocks in zones Cu4 and Cus. Areas of subeconomic mineralization are widespread. A high copper content of soils overlying these rocks, especially in the western part of the quadrangle, is another favorable sign. Zone Cu7 contains volcanic rocks that are in many ways similar to those in zones Cu4 and Cus but that differ in some important details relating principally to
90° 00' 46°00' 25 MILES 35 KILOMETERS FIGURE 2. Generalized mineral-resource map of the Iron River I°x2° quadrangle, Michigan ar
88°00' EXPLANATION IDENTIFIED RESOURCES Areas underlain by reserves Areas where iron-formations are at or near the surface Areas where copper-mineralized rocks are at or near the surface Subsurface extensions of mineralized rocks. For iron-formations a 1-mile (2.6-km) depth cutoff was chosen although units can be inferred confidently to continue to greater depth UNDISCOVERED RESOURCES Areas with class A favorability Areas with class 6 favorability Areas with class C favorability Unconformity near which unconformity-type uranium deposits might occur. Tick-marks are on side of unconformity where older rocks are found Unconformity near which uraniferous phosphate deposits might be found. Tick-marks are on side of unconformity where deposits are probable Ss-i, Fe3, Identifying symbols for specific resource-potential areas. See text for and so on details Wisconsin. Modified from Cannon (1983a). Base from U.S. Geological Survey, 1958 (1:250,000).
composition of the rocks. No substantial copper mineralization is known. The existence of undiscovered native copper deposits is possible but seems less likely here than it is in zone Cu6. is ranked class A because it shows geophysical anomalies and contains favorable rock types and also subeconomic copper and zinc mineralization. IRON Undiscovered deposits of iron ore could exist in any of zones Fe, through Fe7, which are all within or are extensions of past mining districts. Such ores are of limited importance in the short term and are not likely to be explored for in the foreseeable future. SPECULATIVE RESOURCES Speculative resources are those that possibly exist but that, if found, would be a new type of deposit for the region. Several genetic types of speculative resources are discussed here. They are the ones judged most likely to occur. Other types, not discussed, could also occur but, at present, are judged either to have insufficient potential to enter into near-term resource considerations or to have not yet been recognized as possible resources. VOLCANOGENIC MASSIVE SULFIDE DEPOSITS Volcanogenic massive sulfide deposits occur in submarine volcanic rocks and generally near centers of volcanic activity. Massive sulfides are generally polymetallic ores that may be mined for copper, lead, zinc, silver, and gold. Areas designated Msi in figure 2 are zones where ancient submarine volcanic rocks are at the bedrock surface and are considered favorable for massive sulfides. In most areas, however, the bedrock is so poorly exposed that few details of the volcanic rocks are known; the belts are defined as class C areas and cannot be further subdivided. Zone Ms2 is a thick unit of submarine volcanic rocks that is considered to be a class B area because it appears to have formed near a volcanic center and, in addition, because it causes several distinctive geophysical anomalies (electromagnetic conductors) that could result from massive sulfide deposits in the subsurface. Zone Ms3 is a belt of submarine volcanic rocks about which few details are known, but that is ranked class B because geophysical anomalies there could be caused by massive sulfide deposits in the subsurface. Zone Ms4 is a small belt west of Lake Gogebic that SEDIMENT-HOSTED SULFIDE DEPOSITS Several types of sediment-hosted sulfide deposits are possible in the quadrangle and could contain ores of copper, zinc, lead, silver, or gold. CARBONATE-SHALE HOSTED DEPOSITS About 30 miles (48 kilometers) east of the quadrangle, near Marquette, Midi., a large subeconomic copper sulfide deposit, estimated to contain 1 billion tons (0.9 billion tonnes) of mineralized rock (Wilband, 1978), occurs in shale beds in a generally dolomitic rock unit. Extensions of the dolomite unit are known in several parts of the quadrangle. Areas containing the dolomite are ranked class C and shown as zones Ssi on the map. Zone Ss2 is ranked class B because geophysical anomalies indicate that subsurface rocks contain either extensive shale beds within the dolomite or possibly sulfide-rich beds. Zone Ss3 is a small area ranked class A because it contains an outcrop of mineralized bedrock. Copper sulfide minerals occur in quartzite beds that are interlayered with dolomite. Grades are locally as high as 1 percent copper (Cannon, 1980). SHALE AND IRON-FORMATION HOSTED DEPOSITS Several areas contain shale and interbeds of ironformation, zones Ss4 in figure 2. Many of these areas are poorly known because of the scarcity of bedrock exposures but are judged to be potential hosts for sulfide deposits of copper, zinc, and lead. Some lowgrade mineralization (generally less than 0.1 percent copper plus zinc) is known locally, and undocumented verbal reports from mining companies indicate discoveries of subeconomic sulfide deposits. Some carbonate-hosted deposits such as those of zones Ssi are also possible within the Ss4 zones. VOLCANIC-SEDIMENT ASSOCIATION Massive and disseminated sulfide deposits sometimes occur at the fringes of submarine volcanic
zones where the volanic rocks are interlayered with submarine sedimentary rocks. Zone Sss is assigned class C favorability because it contains interlayered volcanic rocks, shale, graywacke, and iron-formation. No direct signs of mineralization are known. Zone Ss* is given class A favorability. It contains rocks similar to those in zone Sss but, in addition, is known to contain sulfide-rich rock units that have subeconomic concentrations of copper and zinc. the fringes of iron-ore bodies in the Sherwood and James mines (James and others, 1968). These deposits are of small size and subeconomic grade. Consequently, the belts in which the iron ores of the district occur (zones Fe4 and Fe7) are considered to have class C favorability for uranium. URANIFEROUS PHOSPHATE DEPOSITS DEPOSITS ASSOCIATED WITH MAFIC INTRUSIVE ROCKS Igneous rocks that have undergone strong chemical fractionation as they crystallized from a molten state to solid state may contain concentrations of copper, nickel, cobalt, chromium, or platinum. Such strongly fractionated mafic rocks exist in a few places in the quadrangle, but no mineralization is known in them. Zones Mi, are areas where such rocks are known. Zones Mi2 contain rocks formed in that part of the mafic fractionation sequence in which mineral deposits are most likely to occur. They are assigned class B favorability. UNCONFORMITY URANIUM DEPOSITS During the 1970's, some very rich uranium deposits, some of which also contain nickel and gold, were discovered along ancient erosion surfaces (unconformities) in Australia and Canada. The unconformity extending across the Iron River quadrangle from near the northeast corner to Wakefield has many features in common with those uranium-bearing unconformities. In the late 1970's, many mining companies explored for uranium along the unconformity in the quadrangle. A broad belt parallel to and including the unconformity Uiii is given class C favorability because of similarities between the geology there and that of mineralized unconformities. A zone east of Lake Gogebic (Uu2) is given class B favorability because it contains some of the specific features directly associated with mineralization elsewhere (as noted in the explanation, fig. 2). URANIUM-IRON ASSOCIATION In the Iron River-Crystal Falls district, concentrations of uranium were discovered in several places at In 1976, small deposits of phosphate-rich rock, some with small concentrations of uranium, were discovered at several localities in the northeast part of the quadrangle (Cannon and Klasner, 1976b). Since then, additional low-grade occurrences have been found in the Gogebic Range. All known deposits are very near (within a few hundred feet) the unconformity separating very ancient crystalline rocks from somewhat younger metasedimentary rocks. That unconformity is shown, wherever it is known to exist, in figure 2, and a class C favorability belt is considered to exist along it, although that belt is too narrow to show at this scale. SILVER-BEARING SHALE A belt of black shale and slate in the northeast part of the quadrangle (zone Ag) contains unusually high concentrations of silver, which, in places, are accompanied by molybdenum. Soil overlying these rocks commonly is also silver rich. Although these rocks are far from being economically exploitable for silver or molybdenum, they are considered to have class C favorability for silver or molybdenum deposits because, within the shale belt, some process locally might have further concentrated the widespread high silver and molybdenum values to potentially economic levels. DIAMOND About 15 miles (24 kilometers) northeast of Crystal Falls, a small body of kimberlite was discovered recently (Cannon and Mudrey, 1981). Kimberlite is a rare type of rock and is the only natural source of diamonds. About 1 kimberlite body in 10 contains diamonds. Only one kimberlite occurrence is known in the quadrangle, but it is likely that others exist nearby, so diamond-bearing rocks may exist in the quadrangle.
CONCLUSIONS The Iron River quadrangle is part of a mineral-rich region that contains large identified deposits that are currently or potentially economic to mine. In addition, large areas of promising ground for exploration exist, and future discoveries of presently unknown deposits are possible. Despite the relatively low level of mining in the quadrangle in 1980, the Iron River quadrangle has the potential to produce large amounts of minerals in the future. Within the quadrangle, about 12.2 billion pounds (5.5 billion kilograms) of copper are known to exist in well-studied deposits. Material that is presently economic includes 9.2 billion pounds (4.2 billion kilograms) of copper in the White Pine orebody. At least several billion additional pounds are likely to occur in known mineralized rocks in areas where data do not allow quantification. About 13.25 billion tons (12.02 billion tonnes) of banded iron-formation are estimated to exist within 500 feet (152.4 meters) of the surface in three principal mining districts the Marquette, the Gogebic, and the Iron River-Crystal Falls districts. A small percentage of that material might someday be minable as taconite if improved mining or metallurgical technology or increased iron prices permit profitable extraction of iron. Possibly, parts of the quadrangle contain undiscovered deposits of copper, zinc, lead, silver, uranium, phosphate, nickel, chromium, cobalt, platinum, gold, and diamonds. Future exploration seems likely to find some of these and add to the known mineral wealth of the region. BIBLIOGRAPHY The following references were selected from many publications on the Iron River region because they are considered principal references on the geology of certain areas or certain problems or bear directly on ore deposits and mineral resources of the quadrangle. Each reference includes a brief annotation that indicates the nature of material presented in the publication. Alien, R. C., 1910, The Iron River iron-bearing district of Michigan: Michigan Geological and Biological Survey Publication 3, Geological Series 2, 151 p. Discussion of the iron resources in the Iron River district of Michigan, including maps of individual mines. Also discussion of geology of this district, inchiding a geologic map at 1:31,250 scale (2 inches 1 mile). Mineral resources of Michigan with statistical tables of production and value of mineral products for 1910 and prior years: Michigan Geological and Biological Survey Publication 8, Geological Series 6, 456 p. Discussion of mineral resources of Michigan, statistics of mining industry, and production, including copper and iron. Includes maps of mine locations and yearly production of individual mines. _1920, Mineral resources of Michigan with statistical tables of production and value of mineral products for 1918 and prior years: Michigan Geological and Biological Survey Publication 29, Geological Series 24, 200 p. Discussion of metallic mineral resources (copper and iron) and a statistical review of iron ore shipments by districts from 1905 to 1918. Discussion of nonmetallic minerals, including production tables. Alien, R. C., and Barrett, L. P., 1915, Contributions to the Precambrian geology of northern Michigan and Wisconsin: Michigan Geological and Biological Survey Publication 18, Geological Series 15, p. 13-164. Geologic descriptions of and magnetic data on the eastern part of the Gogebic Iron range and several other iron-bearing areas in the western part of the Iron River quadrangle. Alminas, H. V., Hoffman, J. D., and Hopkins, R. I., 1983a, Copper distribution in B-horizon soils in the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-H, scale 1:250,000. Map showing soil-sample localities and copper contents, in parts per million. Brief text. ___1983b, Chromium distribution in B-horizon soils in the Iron River 1° x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-I, scale 1:250,000. Map showing soil-sample localities and chromium contents, in parts per million. Brief text. _1983c, Interpretive geochemical map of the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-N, scale 1:250,000. Map showing variations in soil compositions derived from multielement correlation of metal contents. Brief text. Anderson, G. J., 1968, The Marquette district, Michigan, in Ore deposits of the United States, 1933-1967 (Graton-Sales volume): New York, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., v. 1, p. 507-517. Discussion of the mining history of the area, the physiographic and geologic history, the economic geology, and the genesis of the ores. Generalized maps and sections, stratigraphic table. Bailey, S. W., and Tyler, S. A., 1960, Clay minerals associated with the Lake Superior iron ores: Economic Geology, v. 55, no. 1, p. 150-175. Discussion of the accessory clay-sized minerals found in the Marquette, Gogebic, and Iron River districts in Michigan. Differences in assemblages between these and the Mesabi, Cuyuna, and Vermillion district of Minnesota indicate different environments of formation. No maps. Balsley, J. R., Jr., Davis, F. J., Nelson, R. A., Reinhardt, P. W., and Stead, F. W., 1950, Airborne radioactivity survey of parts of Marquette, Dickinson, and Baraga Counties, Michigan: U.S. Geological Survey Geophysical Investigations Map, scale 1:126,720. Map showing the approximate locations of radioactive anomalies over an area of about 1,600 mi2 indicating areas in which uranium and thorium may occur. Brief text. Barghoorn, E. S., Meinschein, W. G., and Schopf, J. W., 1965, Paleobiology of a Precambrian shale: Science, v. 148, no. 3669, p. 461-472. Studies on the geology, organic geochemistry, and paleontology of the White Pine area in Michigan to investigate the problem of detection of ancient life. Deals mostly with the Nonesuch Shale.
Barrett, L. P., 1953, A sampling and radiation analysis of the pre-Cambrian rocks of Michigan, Minnesota, and Wisconsin: U.S. Atomic Energy Commission RME-3032, 15 p. Brief description of the general geology of the area and a summary of the results of a scintillometer survey and radiologic sampling of the Precambrian formations. Some indications of uranium and thorium were found. Generalized map. Bayley, R. W., 1959, Geology of the Lake Mary quadrangle, Iron County, Michigan: U.S. Geological Survey Bulletin 1077, 112 p., 7 pis., scale 1:24,000. Detailed geology of a 7'/2-min quadrangle, including descriptions of stratigraphy, structure, magnetic surveys, and economic geology. Geologic and magnetic maps, photographs. Bayley, R. W., Dutton, C. E., and Lamey, C. A., 1966, Geology of the Menominee iron-bearing district, Dickinson County, Michigan, and Florence and Marinette Counties, Wisconsin: U.S. Geological Survey Professional Paper 513, 96 p. Major references on the geology, structure, and economic geology of an area slightly larger than three 7'/2-min quadrangles. Geologic maps and sections, photographs. Bayley, W. S., 1904, The Menominee iron-bearing district of Michigan: U.S. Geological Survey Monograph 46, 513 p. Major reference on an area of 112 mi2 that was one of the major iron ore producers in Michigan. Detailed geology and description of iron ore. Many geologic maps, cross sections, and diagrams. Bodwell, W. A., 1972, Geologic compilation and nonferrous metal potential, Precambrian section, northern Michigan: Houghton, Mich., Michigan Technological University, M.Sc. thesis, 106 p. General geology of area and detailed discussions of locations of nonferrous metal occurrences, especially copper, pyrite, uranium, and gold. Geologic map and numerous tables. Books, K. G., 1968, Magnetization of the lowermost Keweenawan lava flows in the Lake Superior area: U.S. Geological Survey Professional Paper 600-D, p. D248-D254. Discusses correlation of magnetization in the lowermost Keweenawan lava flows on opposite sides of Lake Superior. Uses paleomagnetic data and 145 drill core samples. Includes general geologic map, summary of paleomagnetic data, and diagrams of directions of magnetization. Paleomagnetism of some Lake Superior Keweenawan rocks: U.S. Geological Survey Professional Paper 760, 42 p. Discusses natural remanent magnetization of rocks. Paleomagnetic studies were conducted at the Keweenaw Peninsula, Ironwood-Mellen area, and north shore of Lake Superior. Includes many equal-area diagrams showing direction of remanent magnetizations. Brecke, E. A., 1968, Copper mineralization in the upper part of the Copper Harbor Conglomerate at White Pine, Michigan: Economic Geology, v. 63, no. 3, p. 294. Discussion of color change in shale and limestone and alteration of ferric iron. Attributes change to hydrothermal activity. Broderick, T. M., 1929a, Zoning in Michigan copper deposits and its significance, part I: Economic Geology, v. 24, no. 2, p. 149-162. Arsenic occurs in small quantities in all known Michigan copper deposits. The ratio of arsenic to copper increases with depth. One very generalized map and two graphs of arsenic ratios. ___1929b, Zoning in Michigan copper deposits and its significance, part II: Economic Geology, v. 24, no. 3, p. 311-326. Study of the changes of the ratio of arsenic to copper with depth makes it possible to group formations and predict mineralogical changes likely to occur in mining. It is also possible to extend zones beyond known lode deposits. No map. Fissure vein and lode relations in Michigan copper deposits: Economic Geology, v. 26, no. 8, p. 840-856. Discussion of the relation of fissure veins to lode formation and application of this relation to exploration for new lode deposits of copper. 1952, The origin of Michigan copper deposits: Economic Geology, v. 47, no. 2, p. 215-219. Brief discussion of the differences of opinion on origin of copper held by author and H. R. Cornwall. See other references by these two authors for more details. Copper deposits of the Lake Superior region: Economic Geology, v. 51, no. 3, p. 285-287. Letter in the "Discussion" section comments on author's view that a theory, to be acceptable, must explain all deposits of a district studied. Refers to work done by a USGS team in the Lake Superior region and their proposal of varied modes of origin. Broderick, T. M., and Hohl, C. D., 1935, Differentiation in traps and ore deposition: Economic Geology, v. 30, no. 3, p. 301-312. Study of differentiation in Keweenawan lava flows of the Michigan copper district furnishes new data concerning the amounts of copper and its distribution in the traps. No map; a table of sulfur and copper percentages in various rock types. Broderick, T. M., Hohl, C. D., and Eidemiller, H. N., 1946, Recent contributions to the geology of the Michigan copper district: Economic Geology, v. 41, no. 7, p. 675-725. Discussion of general geology of the area, internal features of orebodies, geologic relations as guides to exploration, and origin of deposits. Very generalized map and cross section and a stratigraphic column. Brown, A. C., 1968, Zoning in the White Pine copper deposit, Ontonagon County, Michigan: Ann Arbor, Mich., University of Michigan, Ph.D. thesis, 194 p. Entertainment of the proposal that mineralization of the basal Nonesuch Formation was accomplished by the introduction of copper from Copper Harbor Formation after burial of Nonesuch sediments. Uses infiltration and diffusion models. An epigenetic origin for stratiform Cd-Pb-Zn, sulfides in the lower Nonesuch Shale, White Pine, Michigan: Economic Geology, v. 69, no. 2, p. 271-274. Proposes an epigenetic origin for layers of Cd-Pb-Zn, which requires the metals to be pulsed to a higher level by an influx of cupriferous solution from the underlying strata. Burnie, S. W., Schwarcz, H. P., and Crocket, J. H., 1972, A sulfur isotopic study of the White Pine mine, Michigan: Economic Geology, v. 67, no. 7, p. 895-914. Discussion on the Nonesuch Shale, including analysis by sulfur extraction, isotopic analysis, carbon analysis, and boron analysis. Butler, B. S., and Burbank, W. S., 1929, The copper deposits of Michigan: U.S. Geological Survey Professional Paper 144, 238 p. Detailed study of copper deposits in northern Michigan. Includes 27 geologic maps and 16 longitudinal sections. Sections include general features, ore deposits, and detailed descriptions of lodes and fissures. Cannon, W. F., 1973, The Penokean orogeny in northern Michigan, in Young, G. M., ed., Huronian stratigraphy and sedimentation: Geological Association of Canada Special Paper 12, p. 251-271. Discussion of the structural style and orogenic sequence of the event known as the Penokean orogeny. Geologic sketch map and numerous cross sections.
_1976, Hard iron ore of the Marquette Range, Michigan: Economic Geology, v. 71, no. 6, p. 1012-1028. Discussion of petrology and origin of specularite and clastic and magnetite ores found in the Marquette Range, Michigan. General geologic map, isometric maps, stratigraphic sections, and photographs included. _1977, Map showing Precambrian geology in parts of the Baraga, Dead River, and Clark Creek basins, Marquette and Baraga Counties, Michigan: U.S. Geological Survey Open- File Report 77-467, 1 pi., scale 1:62,500. Detailed geologic map of the area, no text. _1980, Copper-bearing quartzite near Watersmeet, Michigan: U.S. Geological Survey Open-File Report 80-390, 7 p. Brief description of a copper occurrence in Precambrian quartzite. Includes assays and two maps. _1983a, Mineral resources map of the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous investigations Map I-1360-A, scale 1:250,000. Map showing location of known mineral resources of the quadrangle and zones of potential for undiscovered deposits. Brief text and tables. _1983b, Bedrock geologic map of the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-B, scale 1:250,000. Map showing bedrock geology of the area. Brief text and cross sections. _1983c, Structural and tectonic map of the Iron River 1° x 2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-D, scale 1:250,000. Map showing lithotectonic units and major structures of the quadrangle. Cannon, W. F., and Gair, J. E., 1970, A revision of stratigraphic nomenclature for middle Precambrian rocks in northern Michigan: Geological Society of America Bulletin, v. 81, no. 9, p. 2843-2846. Proposal to introduce the name Marquette Range Supergroup to supplant the term Animikie Series for the middle Precambrian sequence of the Northern Peninsula and areas in Wisconsin. Includes sketch map and stratigraphic correlation chart. Cannon, W. F., King, E. R., Hill, J. J., and Mory, P. C., 1980, Mineral resources of the Sturgeon River Wilderness Study Area, Houghton and Baraga Counties, Michigan: U.S. Geological Survey Bulletin 1465, 49 p. Discussion of geology and geophysical interpretations and investigation of known and potential mineral deposits. General geologic maps, aeromagnetic maps, and partial chemical analysis of samples. Cannon, W. F., and Klasner, J. S., 1975, Stratigraphic relationships within the Baraga Group of Precambrian age, central upper peninsula, Michigan: U.S. Geological Survey Journal of Research, v. 3, no. 1, p. 47-51. Correlation of units between geographically separated areas has been greatly aided by mapping in the Witch Lake 15-min quadrangle. Various iron-formation units can now be correlated. Generalized geologic map and section. ___1976a, Geologic map and geophysical interpretation of the Witch Lake quadrangle, Marquette, Iron, and Baraga Counties, Michigan: U.S. Geological Survey Miscellaneous Investigations Map 1-987, scale 1:62,500. Detailed geologic map of the area, also showing available geophysical information. Brief text on map. ___1976b, Phosphorite and other apatite-bearing sedimentary rocks in the Precambrian of northern Michigan: U.S. Geological Survey Circular 746, 6 p. Brief discussion of occurrences of phosphate with sedimentary rocks in the Precambrian of northern Michigan. Includes a geologic sketch map. Cannon, W. F., and Mudrey, M. G., Jr., 1981, The potential for diamond-bearing kimberlite in northern Michigan and Wisconsin: U.S. Geological Survey Circular 842, 15 p. Describes kimberlite pipe in northern Michigan and historic discoveries of diamonds in glacial drift in Wisconsin. Proposes that diamond-bearing kimberlites exist in Michigan or Wisconsin. Cannon, W. F., Powers, S. L., and Wright, N. A., 1978, Computer-aided estimates of concentrating-grade iron resources in the Negaunee iron-formation, Marquette District, Michigan: U.S. Geological Survey Professional Paper 1045, 21 p. Analysis of resource potential and estimation of the maximum amount of recoverable iron through a statistical simulation model. Includes generalized geologic map, numerous histograms, graphs, and charts. Carpenter, R. H., 1963, Some vein-wall rock relationships in the White Pine mine, Ontonagon County, Michigan: Economic Geology, v. 58, no. 5, p. 643-666. The dominant facies of copper mineralization at White Pine is characterized by the relationship of copper to sedimentary features and by its restriction to the base of the Nonesuch Shale. A second minor facies is fracture controlled and of two types: fracture-filled veins and halos. Chaudhuri, Sambhudas, and Faure, Gunter, 1967, Geochronology of the Keweenawan rocks, White Pine, Michigan: Economic Geology, v. 62, no. 8, p. 1011-1033. Report deals with age determinations made by the Rb-Sr method applied to suites of total-rock specimens and isotope analyses of lead from the White Pine copper mine. Clements, J. M., and Smyth, H. L., 1899, The Crystal Falls ironbearing district of Michigan: U.S. Geological Survey Monograph 36, 512 p., scale 1:125,000. Comprehensive report on an area of 1,300 mi2 in northern Michigan describing the geography, geology, and mining history. Many detailed geologic maps, cross sections, diagrams, and photographs. Cornwall, H. R., 1951, Ilmenite, magnetite, hematite, and copper in lavas of the Keweenawan series: Economic Geology, v. 46, no. 1, p. 51-67. Opaque minerals in 10 lava flows were studied microscopically, and two groups of minerals and their alteration production were distinguished to provide an index to the degree of differentiation of basaltic lavas of the area. No map. Dutton, C. E., 1949, Geology of the central part of the Iron River district, Iron County, Michigan: U.S. Geological Survey Circular 43, 9 p. General geology of an area of 5 mi2. Description of iron-formation, past and present mining, and future possibilities. Geologic maps and sections, mine level maps, magnetic data. Geology and magnetic data for central Iron River area, Michigan: Michigan Geological Survey Division Report of Investigation 5, 17 p., maps, scale 1:6,000. Supplements USGS Professional Paper 570 with detailed geology, descriptions of mines and exploration, and magnetic surveys of the area. Dutton, C. E., and Bradley, R. E., 1970, Lithologic, geophysical, and mineral commodity maps of Precambrian rocks in Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map 1-631, 6 ., scale 1:500,000, 15-p. text. Six maps plus text. Text discusses lithology, aeromagnetic and gravity data, and geology of specific areas as it relates to mineral deposits. Tables show geochronological data and mineral occurrences. Maps show geology, lithology, and geophysical data. One
map shows mineral localities and metamorphic zones extending into northern Michigan. Dutton, C. E., and Linebaugh, R. E., 1967, Map showing Precambrian geology of the Menominee iron-bearing district and vicinity, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map 1-466, scale 1:125,000. Map of an area of about 1,000 mi2 showing geology and ironbearing formations. No text. Ensign, C. O., Jr., White, W. S., Wright, J. C., Patrick, J. L., Leone, R. J., Hathaway, D. J., Trammell, J. W., Fritts, J. J., and Wright, T. L., 1968, Copper deposits in the Nonesuch Shale, White Pine, Michigan, in Ore deposits of the United States, 1933-1967 (Graton-Sales volume): New York, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., v. 1, p. 460-488. Discussion of mining and exploration, physiographic history, general geology, and structure of area. Extensive descriptions of stratigraphy, mineralogy, and form of orebodies as well as their origin and time of mineralization. Sketch maps of geology, structure, and thickness of beds. Fritts, C. E., 1969, Bedrock geologic map of the Marenisco- Watersmeet area, Gogebic and Ontonagon Counties, Michigan: U.S. Geological Survey Miscellaneous Investigations Map 1-576, scale 1:48,000, 5-p. text. Detailed geologic map of three 15-min quadrangles, four cross sections, some aeromagnetic data, and locations of mineralized areas. Gair, J. E., and Wier, K. L., 1956, Geology of the Kiernan quadrangle, Iron County, Michigan: U.S. Geological Survey Bulletin 1044, 88 p., 5 pis., scale 1:24,000. Detailed geology of a 7!/2-min quadrangle, including stratigraphy, structure, magnetic surveys, and economic geology. Geologic maps and sections, magnetic maps, diagrams, tables, and photographs. Good, S. E., and Pettijohn, F. J., 1949, Magnetic survey and geology of the Stager area, Iron County, Michigan: U.S. Geological Survey Circular 55, 4 p. Very generalized geology of an area of 4 mi2 and more detailed magnetic data. Brief description of mining possibilities. Geologic map and magnetic data map. Hamblin, W. K., 1958, The Cambrian sandstones of northern Michigan: Michigan Geological Survey Division Publication 51, 149 p. Comprehensive study of the Cambrian sediments, by means of area! mapping, and a detailed study of stratigraphy, sedimentation, and paleontology. Geologic maps, sections, tables, stratigraphic charts, and many photographs. Hamilton, S. K., 1967, Copper mineralization in the upper part of the Copper Harbor Conglomerate at White Pine, Michigan: Economic Geology, v. 62, no. 7, p. 885-904. Nature and distribution of copper mineralization in the upper parts of the Copper Harbor Conglomerate. Controls of copper distribution and mode of origin are discussed. Heran, W. D., and Smith, B. D., 1980, Description and preliminary map, airborne electromagnetic survey of parts of Iron, Baraga, and Dickinson Counties, Michigan: U.S. Geological Survey Open-File Report 80-297, 13 p., 1 sht., scale 1:62,500. Map showing location and magnitude of electromagnetic anomalies. Brief text describing method of survey. Hobbs, W. H., 1899, The diamond field of the Great Lakes: Journal of Geology, v. 7, p. 375-388. Text covers physical characteristics of the lake diamonds, their distribution, and their origin. Hoffman, J. D., Alminas, H. V., and Hopkins, T. R., 1983a, Cobalt distribution in B-horizon soils in the Iron River 1° x 2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-J, Scale 1:250,000. Map showing soil-sample localities and cobalt contents, in parts per million. Brief text. _1983b, Nickel distribution in B-horizon soils in the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-K, scale 1:250,000. Map showing soil-sample localities and nickel contents, in parts per million. Brief text. Hopkins, T. R., Alminas, H. V., and Hoffman, J. D., 1983a, Silver distribution in B-horizon soils in the Iron River 1° x 2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-L, scale 1:250,000. Map showing soil-sample localities and silver contents, in parts per million. Brief text. ___1983b, Molybdenum distribution in B-horizon soils in the Iron River 1° x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-M, scale 1:250,000. Map showing soil-sample localities and molybdenum in parts per million. Brief text. Hubbard, H. A., 1974, Bedrock geology of the Porcupine Mountains, Michigan: U.S. Geological Survey Open-File map, scale 1:62,500. Detailed geologic map of the area. No text. ___1975a, Geology of Porcupine Mountains in Carp River and White Pine quadrangles, Michigan: U.S. Geological Survey Journal of Research, v. 3, no. 5, p. 519-528. Detailed geology of an area of 75 mi2 and descriptions of stratigraphy and structure. Geologic map and cross sections and stratigraphic correlation table. ___1975b, Lower Keweenawan volcanic rocks of Michigan and Wisconsin: U.S. Geological Survey Journal of Research, v. 3, no. 5, p. 529-541. Detailed geology of an area of about 70 mi2 showing new correlations and stratigraphic nomenclature between rocks of unconformable sequences of Keweenawan volcanic rocks. Geologic map, chemical analyses, and stratigraphic table. Irving, R. D., and Van Hise, C. R., 1890, The Penokee ironbearing series of Michigan and Wisconsin: U.S. Geological Survey Monograph 19, 534 p. A summary of previous work on the area and a detailed description of the current geology, with emphasis on the iron-bearing formations. Geologic maps, diagrams, and sections. James, H. L., 1951, Iron formation and associated rocks in the Iron River district, Michigan: Geological Society of America Bulletin, v. 62, no. 3, p. 251-266. Discussion of origin of ironformation linking climate with other factors. Includes tables showing stratigraphic succession in the Iron River district and chemical analysis of graphite slate, iron-formation, graywacke, and magnetic ironstone. Origin of the soft iron ores of Michigan: Economic Geology, v. 48, no. 8, p. 726-728. A letter in the "Discussion" section on the theory of soft iron ore formation in Michigan as proposed by V. I. Mann versus other ideas as proposed by USGS. Zones of regional metamorphism in the Precambrian of northern Michigan: Geological Society of America Bulletin v. 66, no. 12, pt. 1, p. 1455-1487. General discussion of geology of the area of 7,500 mi2. Detailed discussion of the metamorphism of the rocks and its relationship to intrusive rocks and structure. Tables and diagrams. Stratigraphy of pre-Keweenawan rocks in parts of northern Michigan: U.S. Geological Survey Professional Paper 314-C, p. C27-C44. Discussion of stratigraphic nomenclature used for lower and middle Precambrian rocks
in Iron and Dickinson Counties and detailed description of various lithologies. Proposes correlation of layered rock sequence containing the iron-formations with Animikie series. Generalized geologic map and stratigraphic tables. James, H. L., Clark, L. D., Lamey, C. A., and Pettijohn, F. J., 1961, Geology of central Dickinson County, Michigan: U.S. Geological Survey Professional Paper 310, 176 p., 1 pi., scale 1:24,000. Extensive summary of the geology of an area of 250 mi2 and detailed discussions of stratigraphy, structure, and economic geology. Iron ore is principal mineral resource. Other minerals are dolomite and uranium. Geological and geophysical maps and stratigraphic and chemical analysis tables. James, H. L., and Dutton, C. E., 1951, Geology of the northern part of the Iron River district, Iron County, Michigan: U.S. Geological Survey Circular 120, 12 p. General geology of an area of 12 mi2. Description of stratigraphy and brief discussion of iron-formation and future mining possibilities. Geologic maps and cross sections, stratigraphic chart, and magnetic data. James, H. L., Dutton, C. E., Pettijohn, F. J., and Wier, K. L., 1968, Geology and ore deposits of the Iron River-Crystal Falls district, Iron County, Michigan: U.S. Geological Survey Professional Paper 570, 134 p., 4 pis., scale 1:24,000. Detailed discussion of geology of an area of 300 mi2 . Stratigraphy, structure, and ore deposits described, as well as ore mineralogy. Iron is chief ore. Uranium present. Geologic maps, stratigraphic charts, chemical analyses, and production data. James, H. L., Dutton, C. E., and Wier, K. L., 1967, Geologic and magnetic data for northern Iron River area, Michigan: Michigan Geological Survey Division Report of Investigation 4, 46 p., maps, scale 1:6,000. Supplements USGS Professional Paper 570 with detailed geology, descriptions of mines and explorations, and magnetic surveys of the area. James, H. L., Pettijohn, F. J., and Clark, L. D., 1970, Geology and magnetic data between Iron River and Crystal Falls, Michigan: Michigan Geological Survey Division Report of Investigation 7, 17 p., maps, scale 1:6,000. Supplements USGS Professional Paper 570 with detailed geology, descriptions of mines and explorations, and magnetic surveys of the area. James, H. L., and Wier, K. L., 1948, Magnetic survey and geology of the eastern and southeastern parts of the Iron River district, Iron County, Michigan: U.S. Geological Survey Circular 26, 18 p., 4 pis. Discussion of geology in the eastern and southeastern parts of the Iron River district and detailed section-by-section descriptions. Includes a stratigraphic chart of characteristics of the iron-formation. Maps include: (1) Geologic cross section in eastern and southeastern parts of the Iron River District, scale 1:2,400. (2) Inferred geology in southeastern part of Iron River district, scale 1":6,000. (3) Magnetic data in southeastern part of Iron River District, scale 1:6,000. (4) Magnetic data and inferred geology in eastern part of the Iron River district, scale 1:6,000. Geology and magnetic data for the southeastern Iron River area, Michigan: Michigan Geological Survey Division Report of Investigation 6, 30 p., maps, scale 1:6,000. Supplements USGS Professional Paper 570 with detailed geology, descriptions of mines and explorations, and magnetic surveys of the area. Johnson, R. F., and White, W. S., 1969, Preliminary report on the bedrock geology and copper deposits of the Matchwood quadrangle, Ontonagon County, Michigan: U.S. Geological Survey Open-File Report, 29 p., I pi. scale 1:62,500. Discussion of general geology, stratigraphy, structure, and economic geology of a 15-min quadrangle. Black and white geologic map. Jolly, W. T., 1974, Behavior of Cu, Zn, and Ni during prehnitepumpellyite rank metamorphism of Keweenawan basalts, northern Michigan: Economic Geology, v. 69, no. 7, p. 118-1125. Study of metamorphic zonation and its affect on metal distribution. Native copper deposits appear to be formed by leaching of copper in higher temperature zones and reprecipitation in lower temperature zones. Kalliokoski, J. O. K., 1976, Uranium and thorium occurrences in Precambrian rocks, Upper Peninsula of Michigan and northern Wisconsin: Houghton, Mich., Michigan Technological University, 274 p. Regional geologic setting and detailed geologic descriptions of known occurrences of uranium and thorium. Contains detailed maps of most occurrences and assay data for most. King, Elizabeth, 1983, Aeromagnetic map of the Iron River 1° x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-F, scale 1:250,000. Map showing variations in magnetic field of the area. Klasner, J. S., and Cannon, W. F., 1974, Geologic interpretation of gravity profiles in the western Marquette district, northern Michigan: Geological Society of America Bulletin, v. 85, no. 2, p. 213-218. Interpretation of gravity profiles, specifically of the Marquette Trough near Humboldt, Mich., the Marquette Trough near Michigamme, Mich., the Republic Trough, and the Michigan River Trough. Includes gravity profiles, geologic sections, stratigraphic column, and gravity models. Bedrock geologic map of the southern part of the Michigamme and Three Lakes quadrangles, Marquette and Baraga Counties, Michigan: U.S. Geological Survey Miscellaneous Investigations Map 1-1078, scale 1:24,000. Detailed geologic map and text covering stratigraphy, structure, metamorphism, and iron resources. Includes table of mine production from the Negaunee Iron-formation and the Bijiki Ironformation Member of the Michigamme Formation. Klasner, J. S., and Jones, W. J., 1983, Bouguer gravity anomaly map and geologic interpretation of the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-F, scale 1:250,000, 2 . Map showing variations in gravitative attraction. Includes additional maps of computer-filtered data. Brief text. Klein, Ira, 1939, Microcline in the native copper deposits of Michigan: American Mineralogist, v. 24, no. 10, p. 643-650. Studies of the distribution, nature, and paragenesis of an unusual variety of microcline found in copper-rich areas of Michigan. Lane, A. C., 1911, The Keweenaw Series of Michigan: Michigan Geological and Biological Survey Publication 6, Geological Series 4, v. 1 and 2, 984 p. Major references on geology and copper deposits of area and detailed descriptions of stratigraphy of each deposit. Geologic maps and sections, diagrams, and tables. Native Silver in an iron mine [abs.]: Geological Society of America Bulletin, v. 35, no. 1, p. 127-128. Brief abstract discussing origin and inclusion of silver in Michigan iron-formations. Leith, C. K., Lund, R. J., and Leith, Andrew, 1935, Pre- Cambrian rocks of the Lake Superior region: U.S. Geological
Survey Professonal Paper 184, 34 p. Revised Precambrian geology of the area surrounding Lake Superior, approximately 550x350 mi. Discussion of stratigraphy and origin of the iron-formation. Geologic map, structure sections, and stratigraphic chart. Mancuso, J. J., Lougheed, M. S., and Shaw, R., 1975, Carbonateapatite in Precambrian cherty iron-formation, Baraga County, Michigan: Economic Geology, v. 70, no. 3, p. 583-586. Report on the occurrence of carbonate-apatite from ironformations in the Upper Peninsula of Michigan. Infers that this occurrence lends credibility to hypothesis that biota were present during deposition of Precambrian cherty ironformations. Includes two pages of photographs. Mann, V. I., 1953, The relation of oxidation to the origin of soft iron ores of Michigan: Economic Geology, v. 48, no. 4, p. 251-281. Discussion of views regarding soft iron-ore development in the Marquette and Gogebic Ranges, the major and minor minerals of the iron-formation and their alteration, and the thermodynamics of the system. Generalized map of Marquette Range. Marsden, R. W., 1968, Geology of the iron ores of the Lake Superior region in the United States, in Ore deposits of the United States, 1933-1967 (Graton-Sales volume): New York, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., v. I p. 489-506. Discussion of mining history, physiography, geologic history, and stratigraphy of region. Description of various types of Lake Superior iron ores and their origin. Generalized geologic and locality maps and production table. Peterson, W. L., 1983, Surficial geologic map of the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-C, scale 1:250,000. Map showing distribution of unconsolidated surficial deposits. Brief text outlining glacial history of the area. Pettijohn, F. J., 1970, Geology and magnetic data for northern Crystal Falls area, Michigan: Michigan Geological Survey Division Report of Investigation 8, 23 p., scale 1:4,750. Supplements USGS Professional Paper 570 with detailed geology, descriptions of mines and explorations, and magnetic surveys of the area. Geology and magnetic data for southern Crystal Falls area, Michigan. Michigan Geological Survey Division Report of Investigation 9, 31 p., maps, scale 1:4,500. Supplements USGS Professional Paper 570 with detailed geology, descriptions of mines and explorations, and magnetic surveys of the area. Pettijohn, F. J., Gair, J. E., Wier, K. L., and Prinz, W. C., 1969, Geology and magnetic data for Alpha-Brule River and Panola Plains areas, Michigan: Michigan Geological Survey Division Report of Investigation 10, 12 p., maps, scale 1:6,000. Supplements USGS Professional Paper 570 with detailed geology, description of mines and explorations, and magnetic surveys of the area. Prinz, W. C., 1967, Pre-quaternary geologic and magnetic map and sections of part of the eastern Gogebic Iron Range, Michigan: U.S. Geological Survey Miscellaneous Investigations Map 1-497, scale 1:10,000. Map of an area of about 6 mi2 showing geology and magnetic data and cross sections. Map text describes past exploration and future possibilities for iron mining. Prinz, W. C., and Hubbard, H. A., 1975, Preliminary geologic map of the Wakefield quadrangle, Gogebic County, Michigan: U.S. Geological Survey Open-File Report 75-119, 12 p., 1 pi., scale 1:24,000. Detailed geologic map of 7'/2-min quadrangle in black and white. No text. Pumpelly, Raphael, 1871, The paragenesis and derivation of copper and its associates on Lake Superior: American Journal of Science, 3d ser., v. 2, no. 10, p. 188-198, 243-258, 347-355. List of mines and description of their contents. Schmidt, R. G., 1980, The Marquette Range Supergroup in the Gogebic iron district, Michigan and Wisconsin: U.S. Geological Survey Bulletin 1460, 96 p. Detailed petrographic descriptions of Proterozoic X strata including the Ironwood Ironformation. Generalized geologic map. Snelgrove, A. K., Seaman, W. A., and Ayres, V. L., 1943, Strategic minerals investigations in Marquette and Baraga Counties: Michiganm Geological Survey Progress Report 10, p. 1-67. Studies of the Marquette iron range, the Lake Michigamme area, the Republic area, and the Ishpeming gold range for locating strategic and rare minerals. Includes a geologic column for the Lake Superior region in general and the Marquette iron range in particular. Snider, D. C., compiler, 1976, General geologic map of the Keweenawan copper range and adjacent areas of Michigan: Michigan Geological Survey Division Map 3867, scale 1:250,000. Generalized geologic map in black and white. No text. Stoiber, R. E., and Davidson, E. S., 1959, Amygdule mineralzoning in the Portage Lake Lava Series, Michigan copper district, pt. 2: Economic Geology, v. 54, no. 8, p. 1444-1460. Discussion of the origin and location of copper deposits with respect to amygdule minerals formed by regional hydrothermal alteration of basaltic lava flows. Supports metamorphic origin of copper rather than a magmatic origin. Studied mineralogy of amygdaloidal rock from mine dumps and the mineralogy of the Kearsarge Flow. Concludes that copper will be found at the outer limit of the regional quartz zone owing to pumpellyitization of basalts. Trent, V. A., 1973, Geologic map of the Marenisco and Wakefield NE quadrangles, Gogebic County, Michigan: U.S. Geological Survey Open-File map, 4 ., scale 1:20,000. Detailed geologic map of the area. Brief text. Tyler, S. A., 1949, Development of Lake Superior soft iron ores from metamorphosed iron formation: Geologic Society of America Bulletin, v. 60, no. 7, p. 1101-1124. Review of two theories of the origin of Lake Superior soft ores. Reexamines the character and distribution of the metamorphic facies of the iron-formations and the nature of ferruginous cherts and the ore. Tyler, S. A., Barghoorn, E. S., and Barrett, L. P., 1957, Anthracitic coal from the Precambrian upper Huronian black shale of the Iron River district, northern Michigan: Geological Society of America Bulletin, v. 68, no. 10, p. 1293-1304. Discussion of carbonaceous shale, anthracitic carbon, and evidence for biogenic origin of graphitic coal. Tyler, S. A., Marsden, R. W., Grout, F. F., and Thiel, G. A., 1940, Studies of the Lake Superior pre-Cambrian by accessory-mineral methods: Geological Society of America Bulletin, v. 51, no. 10, p. 1429-1537. Generalized geology and detailed descriptions of the accessory minerals found in each of the various Precambrian units of the area around Lake Superior. Generalized or sketch geologic maps and tables of mineral analyses. U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, 5 p. Discussion of the
philosophy of mineral-resource classification and definitions of resource terminology. Van Hise, C. R., and Bayley, W. S., 1897, The Marquette ironbearing district of Michigan, with atlas: U.S. Geological Survey Monograph 28, 608 p., atlas of 39 . folio. Major reference on geology of an area of about 100 mi2. Detailed descriptions of geology. Maps, diagrams, and photographs. Van Hise, C. R., and Leith, C. K., 1911, The geology of the Lake Superior region: U.S. Geological Survey Monograph 52, 641 p. Major reference on geology of entire area around Lake Superior. Detailed discussion of geology and mineral deposits. Many geologic maps, cross sections, and diagrams. Vickers, R. C., 1953, Reconnaissance for uranium in the United States, north-central district, in Geologic investigations of radioactive deposits, semiannual program report, June 1 to November 30, 1953: U.S. Geological Survey Trace Elements Investigations TEI-390, p. 202-205. Brief descriptions of radioactive deposits in Baraga and Marquette Counties, Michigan. Uranium minerals and monazite were found. No map. Origin and occurrences of uranium in northern Michigan: U.S. Geological Survey Open-File Report, 76 PJ, 7 figs. A comprehensive report describing the occurrences of uranium in northern Michigan. Generalized geologic map showing locations of occurrences, cross sections, and tables. White, W. S., 1950, Radiometric scanning of collections of. Keweenawan rocks of the Michigan copper-district: U.S. Geological Survey Trace Elements Memorandum TEM-37, 7 p. Geiger-counter tests run on drill cores and rocks and mineral specimens from the surface, mine dumps, and underground did not indicate any significant radioactivity. The most promising material is from the Nonesuch Shale. ___1960a, The Keweenawan lavas of Lake Superior, an example of flood basalts: American Journal of Science, v. 258-A, p. 367-374. Discussion of lava flows of Keweenawan age in the Lake Superior Basin compared to lava flows from shield volcanoes. Uses volume, slope, and direction of flow for basis of comparison. Includes longitudinal stratigraphic section. ___1960b, The White Pine copper district: Economic Geology, v. 55, no. 2, p. 402-409. Letter discussing different theories of ore formation in the White Pine district as argued by the author versus Reno Sales. Tectonics of the Keweenawan basin, western Lake Superior region: U.S. Geological Survey Professional Paper 524-E, 23 p. Discussion of subsurface structure in the Keweenawan Basin includes information on surface geology. General geologic map, two gravity maps, general aeromagnetic map, gravity map, gravity and aeromagnetic profile, and map of major tectonic elements. The native-copper deposits of Northern Michigan, in Ore deposits of the United States, 1933-1967 (Graton-Sales Volume): New York, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., v. 1, p. 303-325. Discussion of geologic and mining history of the area and the genesis of ore. Three generalized geologic maps, cross sections, and tables. A paleohydrologic model for mineralization of the White Pine copper deposit, northern Michigan: Economic Geology, v. 66, no. 1, p. 1-13. Discussion of a quantitative view of lateral migrations of fluids to the White Pine copper deposit through the subjacent Copper Harbor Conglomerate. The base of the Upper Keweenawan, Michigan and Wisconsin; U.S. Geological Survey Bulletin 1354-F, 23 p. Proposal that the top of the Copper Harbor Conglomerate be adopted as the base of the upper Keweenawan and the Oronto Group. Uses paleomagnetic and seismic data. Includes two stratigraphic sections and a diagram of mean directions of magnetization for some Keweenawan rocks. White, W. S., and Wright, J. C., 1950, Radioactivity of the Nonesuch Shale, White Pine Mine, Ontonagon County, Michigan: U.S. Geological Survey Trace Elements Memorandum TEM-158, 4 p. Beta-gamma counts were made on the Nonesuch Shale in the Bill Schacht shaft of the White Pine mine. Discussion of the stratigraphy of the mine, methods of sampling, and findings. Shaft map and several figures and tables. Lithofacies of the Copper Harbor Conglomerate, Northern Michigan: U.S. Geological Survey Professional Paper 400-B, p. B5-B8. Brief discussion of the Copper Harbor Conglomerate accompanied by (1) a map of the distribution of Copper Harbor Conglomerate and its oriented sedimentary structures and (2) a stratigraphic cross section of the Copper Harbor Conglomerate. Sulfide-mineral zoning in the basal Nonesuch Shale, northern Michigan: Economic Geology, v. 61, no. 7, p. 1171-1190. Description of the mineral zoning of the Nonesuch Shale, including discussion of copper. Whitelow, J. W., 1974, Geologic map of the Greenland and Rockland quadrangles, Ontonogan County, Michigan: U.S. Geological Survey Miscellaneous Field Studies Map MF-596, scale 1:62,500. Detailed geologic map of the area. Brief text on map. Wier, K. L., 1967, Geology of the Kelso Junction quadrangle, Iron County Michigan: U.S. Geological Survey Bulletin 1226, 47 p., 3 pis., scale 1:24,000. Detailed geology of 7 1/2-min quadrangle. Brief description of iron-bearing strata and mention of cobalt, copper, and nickel. Geologic map of magnetic data, aeromagnetic profiles, and rock analyses. Geology and magnetic data for northeastern Crystal Falls area, Michigan: Michigan Geological Survey Division Report of Investigation 11, 14 p., maps, scale 1:6,000. Discussion of geology, stratigraphy, structure of an area of 9 mi2 , descriptions of the mines, and magnetic data collected by section. Two geologic sketch maps. Supplements USGS Professional Paper 570. Wier, Karen, 1983, Metamorphic map of the Iron River I°x2° quadrangle, Michigan and Wisconsin: U.S. Geological Survey Miscellaneous Investigations Map I-1360-G, scale 1:250,000. Map showing the distribution of zones of metamorphic intensity developed during three periods of regional metamorphism. Brief text. Wilband, J. T., 1978, The copper resources of northern Michigan: East Lansing, Mich., Michigan State University Geology Department, 66 p. Discussion of known and potential reserves of copper in northern Michigan. Includes nine tables of production by lode and mine, exploration diamonddrill data, and production figures. Maps and stratigraphic sections are also included. Zietz, Isidore, Karl, J. H., and Ostrom, M. E., 1977, Preliminary aeromagnetic map covering most of the exposed Precambrian terrane in Wisconsin: U.S. Geological Survey Miscellaneous Field Studies Map MF-888, scale 1:250,000. Contoured map showing variations in total intensity magnetic field of the Earth in gammas.
Zietz, Isidore, and Kirby, J. R., 1971, Aeromagnetic map of the western part of the northern peninsula, Michigan, and part of northern Wisconsin: U.S. Geological Survey Geophysical Investigations Map GP-750, scale 1:250,000. Spectrally colored contoured map showing variations in total intensity magnetic field of the Earth in gammas.