UNITED STATES DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY MINERAL RESOURCES OF THE BOB MARSHALL WILDERNESS AND STUDY AREAS, LEWIS AND CLARK, TETON, PONDERA, FLATHEAD, LAKE, MISSOULA, AND POWELL COUNTIES, MONTANA by U.S. Geological Survey and U.S. Bureau of Mines Open-file report 78-295 1978 This report is preliminary and has not been edited or reviewed for conformity with U.S. Geological Survey standards and nomenclature. CONTENTS Page Summary III Chapter A. Geology of the Bob Marshall Wilderness and study areas. Introduc t ion 2 Previous studies 5 Present investigations and acknowledgments 5 Geologic setting 6 Precambrian sedimentary rocks 9 Greyson Formation 10 Spokane and Empire Formations 10 Helena Formation 13 Snowslip"Formation 14 Shepard Formation 16 Mount Shields Formation 17 Bonner Quartzite 18 McNamara Formation 19 Garnet Range Formation 20 Cambrian rocks 21 Devonian rocks 23 Mississippian rocks 25 Jurassic and Cretaceous rocks 26 Cretaceous rocks 31 Tertiary rocks 33 Surficial deposits 34 Igneous rocks 35 Precambrian sills 35 Structure 36 References 4 7 Page Chapter B. Aer©magnetic and gravity studies of the Bob Marshall Wilderness and study areas. Introduction 53 Aeromagnetic studies 54 Reconnaissance gravity studies 55 Detailed gravity studies 56 Northeasterly geophysical trends 58 Conclusions 5 8 References 59 Chapter C. A geological and geochemical evaluation of the mineral resources of the Bob Marshall Wilderness and study areas. Introduc tion 62 Methods of evaluation 63 Interpretation of geochemical data 68 Types of deposits 95 Stratabound copper-silver deposits 95 Stratabound lead-zinc and copper-silver deposits in carbonate rocks 99 Vein deposits with copper-lead-zinc-silver in Precambrian diorite sills 100 Vein deposits of barite 100 Limestone and dolomite deposits in the Paleozoic Formations 101 References 103 ii Page Chapter D. Petroleum evaluation of the Bob Marshall Wilderness and study areas. Introduction 106 Outcropping rocks 107 Eastern part 107 Central and western part 116 Structural considerations 117 Hydrocarbon source rock evaluation 121 Conclusions 135 References 137 Chapter E. Economic appraisal of the Bob Marshall Wilderness and study areas. Introduction --------------------------------------------------- Previous studies 142 Present studies and acknowledgments 142 Methods of evaluation 142 Setting 143 Mining claims 143 Sampling and analytical methods 143 Resource classification 144 Mineral commodities and economic considerations 145 Oil and gas 145 Barite 145 ' Copper 146 Silver 146 Coal 146 Sand and gravel and stone 147 Mines, prospects, and mineralized areas 147 Felix Creek-Hoke Creek area 147 Felix Creek prospects (copper-silver) 157 Unawah Creek prospects (copper-silver) 157 South Fork Logan Creek prospects (copper-silver) 157 One Dead Digger prospect 158 Half Man prospect 161 Other L & M prospects 161 Jeanette and Little Darling claims 162 Hoke Creek prospects (copper-silver) 162 Glacier prospect (barite) 167 Teton Pass coal prospects 173 Goat Ridge prospect (zinc-copper-silver) 180 Oil and gas prospects 184 Other prospects and occurrences 184 References 184 iii Illustrations Page Figure 1. Map showing the areas of mineral resource potential in the Bob Marshall Wilderness and adjacent study 2. Index map of part of northwestern Montana showing the location of the Bob Marshall Wilderness and study areas 3 3. View northwest of the Chinese Wall and Continental Divide 4 4. Bob Marshall Wilderness and study areas, northwestern Montana 7 5. Correlation of Precambrian Y belt supergroup in the eastern outcrop area, northwestern Montana 8 6. View north of Precambrian rocks in ridges north of Camp Creek 14a 7. View north of upper reaches of White River showing Fault Peak in foreground (Devonian rocks) 22 7a. Measured sections of the Ellis Group, in and adjacent to the eastern part of the study area 28 7b. Location of measured sections of Ellis Group 29 7c. Measured sections of the Lower Cretaceous unnamed formation in eastern part of the Great Bear Wilderness study area 30 8. Lineaments in the Bob Marshall Wilderness and study areas 40 8a. Geologic cross section in the western part of Great Bear Wilderness study area 41 8b. Geologic longitudinal section in western part of Great Bear Wilderness study area 42 8c. Geologic cross section across the eastern part of Great Bear Wilderness study area and the northern part of the Bob Marshall Wilderness 43 8d. Location of cross and longitudinal sections shown in in figures 8a, b, c 44 9. Index and explanation to the geochemical distribution maps showing the generalized geology 86 lOa, b, c. Distribution map of selected anomalous values of copper, lead, and silver in stream sediments, showing the generalized geology 87 lla, b, c. Distribution map of selected anomalous values of copper, lead, and silver in rocks, showing the generalized geology 90 12. Photograph of mineralized green beds in the Spokane Formation 96a 13. Map of a part of northwest Montana showing oil and gas fields, abandoned or shut-in gas wells, and structural features 108 iv 14. Correlation chart Bob Marshall Wilderness, Sweetgrass Arch, and southern Alberta Foothills 109 15. Map of southern Canada and adjacent Montana 113 16. Geologic cross section in Blackleaf Creek 119 17. Geologic cross section of Waterton Gas Field in southern Alberta and adjacent area in southeastern British Columbia, northwest of Glacier National Park 120 18. Location of hydrocarbon source rock samples 123 19. Hydrocarbon potential of the Bob Marshall Wilderness and study areas 129 20. Map showing mines, prospects, and mineralized areas 148 21. Map showing Felix Creek-Hoke Creek area 149 22. Map showing One Dead Digger prospect 161 23. Map showing Hoke Creek prospects 163 24. Map showing Glacier prospect 174 25. Photo showing west barite outcrop; view looking southerly 176 26. Map showing Teton Pass coal prospects 177 27. Map showing Goat Ridge prospect 181 28. Photo of diorite sill at Goat Ridge prospect; view looking westerly to pit at sample locality 1 183 v Tables Page Table 1. Sedimentary rock units in study area 11 2. Distribution of rock samples by geologic units or by geologic age 65 3. Elements determined by the semiquantitative spectre- graphic technique and the lower limits of detection 67 4. Geometric mean and percentage of anomalous values of copper and lead in selected categories of unbiased samples 69 5. Analytical results of selected anomalous stream sediment and rock samples from the Bob Marshall Wilderness and study areas 71 6. Samples from the Precambrian Formations with anomalous amounts of copper, silver, lead, and molybdenum, and number of anomalous pairs 94 7. Average calcium and magnesium content of some Paleozoic carbonate rocks in and near the Bob Marshall Wilderness and study areas 102 8. Shut-in-gas wells in the northern disturbed belt of Montana 111 9. Gas fields of the Alberta Foothills (north to south) 112 10. Analyses of outcrop and core samples 124 11. Data on wells from which core samples were analyzed and listed on table 10 126 12. Example analyses of "typical" source rocks, Rocky Mountain region 127 13. Vitrinite reflectance, values for selected samples 134 14. Core hole A 168 15. Core hole A-2 169 16. Core hole B 171 17. Summary of other prospects and occurrences 185 vi STUDIES RELATED TO WILDERNESS In accordance with the Provisions of the Wilderness Act (Public Law 88-577, September 3, 1964) and the Joint Conference Report on Senate Bill 4, 88th Congress, the U.S. Geological Survey and U.S. Bureau of Mines have been conducting mineral surveys of wilderness and primitive areas. Studies and reports of all primitive areas have been completed. Areas officially designated "wilderness," "wild," or "canoe" when the Act was passed were incorporated into the National Wilderness Preservation System, and some of them are currently being studied. The Act provided that areas under consideration for Wilderness designation should be studied for suitability for incorporation into the Wilderness System. The mineral surveys constitute one aspect of the suitability studies. This report discusses the results of a mineral survey of the Bob Marshall Wilderness, proposed additions to the wilderness, and the proposed Great Bear Wilderness, northwestern Montana. -I- MINERAL RESOURCES OF THE BOB MARSHALL WILDERNESS AND STUDY AREAS, LEWIS AND CLARK, TETON, PONDERA, FLATHEAD, LAKE, MISSOULA, AND POWELL COUNTIES, MONTANA by U.S. Geological Survey and U.S. Bureau of Mines Chapter A. Geology of the Bob Marshall Wilderness and study areas By Melville R. Mudge and Robert L. Earhart, U.S. Geological Survey Chapter B. Aeromagnetic and gravity studies of the Bob Marshall Wilderness and study areas By_ M. Dean Kleinkopf, Dolores M. Wilson, and Donald L. Peterson, U.S. Geological Survey Chapter C. A geological and geochemical evaluation of the mineral resources of the Bob Marshall Wilderness and study areas By Robert L. Earhart, U.S. Geological Survey Chapter D. Petroleum evaluation of the Bob Marshall Wilderness and study areas By Melville R. Mudge, Dudley D. Rice, Robert L. Earhart, and George E. Claypool, U.S. Geological Survey Chapter E. Economic appraisal of the Bob Marshall Wilderness and study areas By_ Lawrence Y. Marks, U.S. Bureau of Mines Open-file report 78-295 1978 This report is preliminary and has not been edited or reviewed for conformity with U.S. Geological Survey standards and nomenclature. -II- Studies related to wilderness Mineral resources of the Bob Marshall Wilderness and study areas, Lewis and Clark, Teton, Pondera, Flathead, Lake, Missoula, and Powell Counties, Montana Summary A mineral survey of the Bob Marshall Wilderness and proposed additions, Montana, was initiated in 1969 and completed in 1975. The total area covers about 2,580 sq mi (6,680 km ) of the rugged Swan, Flathead, Lewis and Clark, and Sawtooth Mountains; the wilderness covers about 1,480 sq mi (3,830 km ). The results of the investigations indicate that parts of the area have a high potential for natural gas and a low potential for oil.