STUDIES RELATED TO WILDERNESS PRIMITIVE AREAS CLOUD PEAK, WYOMING GEOLOGICAL SURVEY BULLETIN 1371-C Mineral Resources of the Cloud Peak Primitive Area, Wyoming By THOR H. KIILSGAARD and GEORGE E. ERICKSEN, U.S. GEOLOGICAL SURVEY, and by LOWELL L. PATTEN and CARL L. BIENIEWSKI, U.S. BUREAU of MINES STUDIES RELATED TO WILDERNESS PRIMITIVE AREAS GEOLOGICAL SURVEY BULLETIN 1371-C An evaluation of the mineral potential of the area UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1972 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 72-600242 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price For Sale by Supt Docs Stock Number 2401-00219 STUDIES RELATED TO WILDERNESS PRIMITIVE AREAS In accordance with the provisions of the Wilderness Act (Public Law 88-577, September 3, 1964) and the Conference Report on Senate bill 4, 88th Congress, the U.S. Geological Survey and the U.S. Bureau of Mines are making mineral surveys of wilderness and primitive areas. Areas officially designated as "wilderness," "wild," or "canoe," when the act was passed were incorporated into the National Wilderness Preservation System. Areas classed as "primitive" were not included in the Wilder­ ness System, but the act provides that each primitive area be studied for its suitability for incorporation into the Wilderness System. The mineral surveys con­ stitute one aspect of the suitability studies. This bulletin reports the results of a mineral survey in the Cloud Peak Primitive Area and vicinity, Wyoming. The area discussed in the report includes the primitive area, as defined, and some bordering areas that may come under discussion when the area is considered for wilderness status. CONTENTS Page Summary _____________________________________ Cl Introduction ____________________________________ 2 Character and access ___________________________ 2 Climate and vegetation __________________________ 4 Previous investigations __________________________ 5 Present investigations __________________________ 5 Acknowledgments _____________________________ 6 Geology _________________________________________ 6 Geologic setting and history _______________________ 6 Precambrian rocks _____________________________ 9 Gneiss and migmatite ________________________ 10 Amphibolite and schist _______________________ 11 Granitic rocks _____________________________ 11 Radiometric ages of gneissic and granitic rocks ________ 12 Pegmatite and aplite dikes _____________________ 13 Mafic dikes _______________________________ 14 Paleozoic sedimentary rocks _______________________ 18 Flathead Sandstone _________________________ 18 Gros Ventre Formation and Gallatin Limestone ________ 19 Bighorn Dolomite __________________________ 20 Madison Limestone __________________________ 21 Amsden Formation __________________________ 21 Tertiary gravel _______________________________ 21 Quaternary deposits ____________________________ 22 Structure __________________________________ 26 Aeromagnetic interpretation .________________________ 28 Mineral resources ________________________________ 32 Mineral setting _______________________________ 33 Sampling and analytical techniques __________________ 34 Evaluation of sample data ________________________ 35 Mining claims and prospects ______________________- 37 Claims and prospects within the Cloud Peak study area ___ 37 Wilderness Creek area ____________________- 37 Buckskin prospect ____________________-_ 39 Mail Creek prospect ______________________ 42 Lake Arden vicinity ______________________ 43 Hope Lake prospect ______________________ 44 Rhinehart Lakes area _____________________ 44 Edelman Creek prospects __________________- 45 Medicine Lodge Creek prospects ___________ _ 47 Thayer Lake prospects ____________________- 48 Goose Creek area ________________________ 49 Lower East Goose Creek prospects __________ 49 VI CONTENTS Page Mineral Resources Continued Mining claims and prospects Continued Claims and prospects within the study area Continued Goose Creek area Continued Driar prospect _______________________ C51 Middle East Goose Creek prospects __________ 51« Geneva Pass prospect ___________ _ 51 Elephant Head Lake prospects _______________ 52 Highland Park prospect ________________ 53 Cement Mountain prospect __________________ 53 Rock Creek prospect _________________ _ 54 Lake Angeline prospect ____________ 54 East Tensleep Lake prospect _____________ _ 54 Baby Wagon Creek claims ______ 55 Claims and prospects near but outside the study area _ _ 55 Twin Lakes feldspar prospect ______ 55 Bishop mine ___________________________ 55 Dutch Oven Pass prospect ____________ m_____ 56 Battle Creek prospect _____________________ 57 Bellyache Flats hematite _____________ - 57 Soldier Creek prospect _____________________ 57 Merle Creek prospect ___________________ _ 57 South Paint Rock Creek clay property __________ 58 References ____________________________________ 59 ILLUSTRATIONS . Page PLATE 1. Generalized geologic and magnetic intensity map of the Cloud Peak Primitive Area and vicinity, Wyoming ______In pocket 2. Map of the Cloud Peak Primitive Area and vicinity, Wyoming, showing sample localities, prospects, and mining claims ______________________________In pocket FIGURE 1. Index map of northern Wyoming showing location of Cloud Peak study area ________________________ C3 2-8. Photographs: 2. View looking south along crest of the Bighorn Range 8 3. Banded gneiss of the Bighorns _________ __ 9 4. Granitic gneiss cut by pegmatite and aplite ____ 14 5. View looking north along Soldier Creek __ _ 19 6. Cloud Peak from the east _______________ 24 7. The effects of alpine glaciation ________ _ 25 8. Faulted dolerite dike south of Geneva Pass _ _ 28 9. Sketch map showing location of mining claims, prospects, and mineralized occurrences, Cloud Peak study area _ 38 10. View north from Geneva Pass __ __ _________ __ 52 TABLES __________ Page TABLE 1. Chemical composition, normative minerals, and modes of dolerite dikes in the Cloud Peak Primitive Area, Wyo _ C17 CONTENTS VII Page TABLE 2. Magnetic properties of selected rocks from the Cloud Peak Primitive Area, Wyo ______________________ C29 3. Mean of log-normal distribution values of semiquantitative spectrographic analyses of selected elements of stream- sediment, granite and gneiss, dolerite, and panned-con- centrate samples, Cloud Peak Primitive Area, Wyo __ 35 4. Upper-range values of selected elements in stream-sediment samples, Cloud Peak Primitive Area, Wyo _____ _ 36 5. Analyses of samples of altered or mineralized rocks, Cloud Peak Primitive Area, Wyo _______________-_ 40 6. Analyses of Bureau of Mines samples, Cloud Peak Primitive Area, Wyo _____________________________ 42 STUDIES RELATED TO WILDERNESS PRIMITIVE AREAS MINERAL RESOURCES OF THE CLOUD PEAK PRIMITIVE AREA, WYOMING By THOR H. KIILSGAARD and GEORGE E. ERICKSEN, U.S. Geological Survey, and by LOWELL L. PATTEN and CARL L. BIENIEWSKI, U.S. Bureau of Mines SUMMARY A mineral survey of the Cloud Peak Primitive Area and vicinity, Wyoming, was made in 1970 by the U.S. Geological Survey and the U.S. Bureau of Mines. An aeromagnetic survey was made the same year by the Geological Survey. The study area is along the crest of the scenic Bighorn Range in Bighorn, Johnson, and Sheridan Counties, Wyo. It includes the officially designated Cloud Peak Primitive Area of 137,000 acres plus an additional contiguous 95,000 acres, the study of which was requested by the U.S. Forest Service. The total area studied is 232,000 acres. The Cloud Peak study area is underlain almost entirely by igneous and metamorphic rocks of Precambrian age. The only exception is an area along the southwestern boundary where Precambrian rocks are overlain by a sequence of Paleozoic sedimentary rocks that dip westward into the Bighorn Basin. The Precambrian rocks are offset by many faults; some are of Precambrian age but many others were formed during uplift of the Bighorn Range in Late Cretaceous-early Tertiary and later time. Higher parts of the range were glaciated during Pleistocene time and large moraines cover bedrock in the lower parts of the range. The mineral potential of the area was investigated by studying the record of mining activity, by examining the geology, by searching for evidence of mineral deposits, and by extensive sampling and analysis of rocks showing indications of mineralization and of sediments in streams. The geological, geophysical, and geochemical studies indicate that metallic mineral deposits of commercial value do not occur in the area. Prospecting began in the area during the latter part of the last century. Many localities were prospected but there is neither evidence of actual mining nor recorded mineral production from the area. Samples from the various prospects do not contain appreciable quantities of metals, and none of the prospects that were seen warrant further exploration. All values obtained from the stream-sediment samples are within the expected range of values for rock types exposed in the respective drainage basins. The area has no potential for coal, oil or gas, or for appreciable quantities of nonmetallic minerals. There are no patented mining claims in the area, although county records indicate that unpatented claims have been located in and near the area. Cl C2 STUDIES RELATED TO WILDERNESS PRIMITIVE AREAS INTRODUCTION This report describes the findings of a