Mineral Resources of the Gros Ventre Wilderness Study Area, Teton and Sublette Counties, Wyoming
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Mineral Resources of the Gros Ventre Wilderness Study Area, Teton and Sublette Counties, Wyoming WYOMING - Mineral Resources of the Gros Ventre Wilderness Study Area, Teton and Sublette Counties, Wyoming By FRANKS. SIMONS, J. DAVID LOVE, WILLIAM R. KEEFER, DAVID S. HARWOOD, and DOLORES M. KULIK U.S. Geological Survey, and CARL L. BIENIEWSKI U.S. Bureau of Mines An evaluation of the mineral potential of the area U.S. GEOLOGICAL SURVEY BULLETIN 1591 STUDIES RELATED TO WILDERNESS DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director UNITED STATES GOVERNMENT PRINTING OFFICE: 1988 For sale by the Books and Open-File Reports Section U.S. Geological Survey Federal Center Box 25425 Denver, CO 80225 library of Congress Cataloging in Publication Data Mineral resources of the Gras Ventre Wilderness Study Area, Teton and Sublette Counties, Wyoming. (Studies related to wilderness) (U.S. Geological Survey bulletin; 1591) Bibliography: p. Supt. of Docs. no.: I 19.3:1591 1. Mines and mineral resources-Wyoming-Gros Ventre Wilderness. 2. Gros Ventre Wilderness (yVyo.) I. Simons, Frank S. (Frank Stanton), 1917- . II. Series: Studies related to wilderness-wilderness areas. Ill. Series: U.S. Geological Survey bulletin; 1591. QE75.B9 no. 1591 557.3 s 8H00496 [TN24.W8) [553'.09787'55] 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 Bill4, 88th Congress, the U.S. Geological Survey and the U.S. Bureau of Mines have been conducting mineral surveys of areas that are being considered for Wilderness designation. Results of such surveys are submitted to the President and the Congress and are made available to the public. This report presents the results of a geological and mineral survey of the Gras Ventre wilderness study area located in the Bridger-Teton National Forest in west-central Wyoming. CONTENTS Summary 1 Introduction 2 Previous work 4 Present investigation 5 Acknowledgments 6 Geology, by J. David Love, FrankS. Simons, William R. Keefer, and DavidS. Harwood, U.S. Geological Survey 6 Precambrian rocks 6 Paleozoic rocks 7 Mesozoic rocks 9 Cenozoic rocks 15 Structure 17 Aeromagnetic and gravity studies, by Dolores M. Kulik, U.S. Geological Survey 20 Introduction and methods 20 Summary of area geology 20 Aeromagnetic interpretations 20 Gravity interpretations 21 Conclusions 25 Geochemistry, by Frank S. Simons, U.S. Geological Survey 25 Sampling and analytical program 25 Results of stream-sediment sampling 26 Results of rock sampling 32 Sampling of mineralized rocks 32 Precambrian rocks 32 Cambrian and younger rocks 32 Sampling of unaltered rocks 33 Precambrian rocks 33 Cambrian and younger rocks 33 Mineral commodities, by Frank S. Simons and J. David Love, U.S. Geological Survey 38 Oil and gas 38 Phosphate rock 41 Chromium and nickel 42 Copper 42 Iron 42 Lead 43 Molybdenum 43 Uranium and thorium 44 Vanadium 45 Zinc 45 Other elements 45 Coal 47 Construction materials 47 Geothermal energy resources 47 Economic evaluation of mineral potential, by Carl L. Bieniewski, U.S. Bureau of Mines 47 Mining history and production 47 Sampling and analytical results 48 Contents V Economic evaluation-Continued Prospects and mineralized areas 48 Swift Creek 48 Dell Creek and West Dell Creek 48 Other areas 49 Mineral commodities 54 Coal 54 Oil and gas 55 Phosphate rock 55 Other commodities 58 References cited 59 PLATES [Plates are in pocket] 1. Geologic map and cross sections of the Gros Ventre wilderness study area 2. Aeromagnetic map of the Gros Ventre wilderness study area 3. Sample locality map of the Gros Ventre wilderness study area 4. Geochemical sample locality maps and outcrops of Phosphoria Forma tion: A. Localities of 95 stream-sediment samples anomalous in one or more of 13 elements B. Localities of 111 rock samples anomalous in one or more elements C. Localities of stream-sediment and rock samples analyzed for uranium and thorium D. Distribution of outcrops of Phosphoria Formation and related strata, and sample localities FIGURES 1. Drawing of south front of Gros Ventre Range, Wyoming 2 2. Map showing areas that have potential for mineral resources 3 3. Index map showing location of the Gros Ventre wilderness study area 4 4. Index map showing principal geographic features, roads, and main trails 5 5. Gravity models and generalized cross sections along line C-C' 23 6. Gravity models and generalized cross sections along line G-G' 24 7. Histograms and cumulative frequency curves showing distribution of six elements in 277 stream-sediment samples 28 8. Log-probability graph of six elements in 277 stream-sediment samples 30 9. Generalized structure section across the Gros Ventre Range, north end of Green River Basin, Little Granite anticline, and northeast margin of the Wyoming thrust belt 39 10. Map showing location of coal mines, oil and gas drill holes, mining claims, and Federal oil and gas leases 54 11. Map showing outcrops and resource blocks of Phosphoria Formation and related strata 56 VI Contents TABLES 1. Summary of geologic data on Paleozoic sedimentary rocks 7 2. Summary of geologic data on Mesozoic sedimentary rocks 10 3. Summary of geologic data on Cenozoic sedimentary rocks and uncon- solidated deposits 16 4. Average densities of rock samples of four geologic ages 21 5. Threshold amounts of 13 elements in stream-sediment samples 26 6. Threshold amounts of 13 elements in rock samples 27 7. Means, medians, and thresholds for barium, manganese, and yttrium in 277 stream-sediment samples 30 8. Relationships among eight elements in stream-sediment samples 31 9. Samples of Precambrian mineralized or altered rocks anomalous in one or more selected elements 31 10. Samples of mineralized rock of Cambrian and younger age anomalous in one or more elements 32 11. Samples of Precambrian rocks anomalous in one or more selected elements 33 12. Content of 13 elements in shales 34 13. Samples of shale that contain unusually large amounts of one or more minor elements 35 14. Samples of clastic rocks that contain anomalous amounts of selected elements 36 15. Amounts of selected elements in phosphatic rocks 37 16. Analytical data on samples of iron-rich rocks from the Amsden For mation 43 17. Average uranium and thorium contents and thorium-uranium ratios of stream-sediment samples and five groups of rock samples 44 18. Analyses of samples from and near the Gros Ventre wilderness study area 50 19. Thickness and grade of phosphatic and uraniferous beds used in calculation of phosphate and uranium resources in the Gros Ventre Range 57 20. Phosphate resources in the Gros Ventre Range 58 21. Uranium resources in the Gros Ventre Range 60 22. Analyses of phosphate rock and phosphatic shale sampled in and near the Gros Ventre wilderness study area 62 23. Analyses of limestone and dolomite sampled in the Gros Ventre wilderness study area 62 Contents VII STUDIES RELATED TO WILDERNESS Mineral Resources of the Gros Ventre Wilderness Study Area, Teton and Sublette Counties, Wyoming By Frank S. Simons, J. David Love, William R. Keefer, David S. Harwood, and Dolores M. Kulik, U.S. Geological Survey, and Carl L. Bieniewski, U.S. Bureau of Mines SUMMARY is probably as much as 13,000 ft (4,000 m) thick. Bedrock is concealed by unconsolidated deposits of Quaternary The Gros Ventre wilderness study area has a age over about 10-15 percent of the area. moderate oil and gas resource potential in possible reser Structurally, the Gros Ventre Range is a northwest voir rocks beneath the Cache Creek thrust fault in the trending, broad anticlinal arch with a gently dipping southwest part of the area, and a high phosphate rock northeast limb, interrupted by several folds asymmetrical resource potential in the northeast part of the area. The to the southwest and by one fault of substantial displace potential for other mineral or energy resources in the area ment, and a steeply dipping, thrust-faulted, structurally is low. No minerals have been produced from the study complex southwest limb. The central part of the range area. consists mostly of Paleozoic rocks; Precambrian rocks The Gros Ventre wilderness study area comprises are restricted to the southwest part, and Mesozoic and about 230 mi2 (600 km2) of the Bridger-Teton National consolidated Cenozoic rocks occur for the most part only Forest, directly east of Jackson in west-central Wyoming. well down the flanks. Rocks at the southwest crest of the The study area covers a large part of the Gros Ventre Gros Ventre Range are now 30,000-35,000 ft Range, which rises between the Gros Ventre River to the (9,100-10,700 m) above corresponding rocks in the ad northeast and the Hoback River to the southwest, both joining Hoback Basin to the southwest; this uplift took tributary to the Snake River. Figure 1 shows a view of place along the northeast-dipping Cache Creek thrust the Gros Ventre Range as drawn for an early geological fault and related faults in early Tertiary time. report on the area. The area was studied for its suitabil Areas within the Gros Ventre wilderness study area ity as a wilderness area by the U.S. Forest Service as part that have mineral potential are shown on figure 2. of its roadless area review and evaluation program The Little Granite anticline and the possible exten (RARE II). Nearly all of the area studied and additional sion of its northeast flank beneath the Cache Creek thrust roadless land contiguous to the study area, comprising fault and inside the southwest border of the study area about 448 mi2 (1,160 km2), was designated a wilderness have a moderate potential for oil and gas (fig.