BUREAU OF MINES LIBRARY SPOK.'lr.'~ \1, 11 ('., S£p 1 0 19.r~ 1 fLEASE ifT lJ;. ro ueRAP. Geology and Ore Depostts ofthe Darwin Quadrangle Inyo County, California GEOLOGICAL SURVEY PROFESSIONAL PAPER 368 Prepared in cooperation with the ~ytate of California, Department of Natural Resources, Division of Mines \. I !; i :•j i Geology and Ore Deposits ofthe Darwin Quadrangle Inyo County, California By WAYNE E. HALL and E. M. MAcKEVETT, ]R. G E 0 L 0 G I CAL S U R.V E.Y P R 0 FE S S I 0 N A L PAPER 3 6 8 Prepared in cooperation with the State of California, Department of Natural Resources, Division of Mines I UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1962 UNITED STATES DEPARTMENT OF THE INTERIOR STEW~RT L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS Page Page 1 Cenozoic rocks-Continued Abstract------------------------------------------- Pleistocene ____________________________________ _ Introduction ______________________________________ _ 2 36 Location ______________________________________ _ 2 Olivine basalt. ____________________________ _ 36 Purpose and scope ___________________________ - __ _ 3 Old fanglomerate marginal to Darwin Wash ___ _ ;37 Climate and vegetation _____ - _______________ -- __ - 3 37 RecentLakebeds.--------------------------------- _______________________________________ _ TopographY------------------------------------ 4 39 Water supply __________ ---------- ______ ---_----- 4 Unconsolidated gravels and alluvium _________ _ 39 Previous work and acknowledgments ______________ _ 4 Structure _____ ..,.- ________________________ ·__________ _ 39 Fieldwork _________________ - ___________________ _ 5 Structure of the pre-Tertiary rocks _______________ _ 39 Paleozoic rocks ____________________________________ _ 5 Unconformities ____________________________ _ 39 General features ___________ - ___________________ _ 5 40 Ordovician. system _____________________________ _ 6 Folds-------------------------------------- Darwin Wash syncline~---- _____________ _ 40 Pogonip group _____________________________ _ 6 Darwin Hills overturned syncline ________ _ Eureka quartzite ___________________________ _ 9 40 Ely Springs dolomite _______________________ _ Talc City Hills syncline ________________ _ 42 10 Santa Rosa Hills warp __________________ _ Silurian and Devonian systems ________________ - __ _ 42 11 Faults ____________________________________ _ Hidden Valley dolomite _____________________ _ 11 42 Thrust faults __________________________ _ Devonian system ______________________________ _ 12 42 Lost Burro formatio.n. ______________________ _ 12 Talc City thrust ___________________ _ 42 Davis thrust ______________________ _ Mississippian system _________ p _________________ _ 14 43 Tin Mountain limestone. _______________ - __ -_ 14 Strike-slip faults _______________________ _ 43 Perdido formation. _________________________ _ 17 Mineralized steep strike faults ___________ _ 44 Mississippian and Pennsylvanian(?) systems. ______ _ Foliation ____________ ------- __ ------------- 45 18 Summary _________________________________ _ J.. ee Flat limestone _________________________ _ 18 45 Pcnnsylvanin.n(?) system ________________________ _ 19 Cenozoic structures ____________________________ _ 45 Rest Spring shale. _________________________ _ 19 Metamorphism----------------~-------------------- 46 Pennsylvanian and Permian systems. ____________ _ 21 lgneous metamorphism _________________________ _ 46 Keeler Canyon formation ___________________ _ 22 Metam~rphism within the igneous rocks ______ _ 46 Lower unit. ___________________________ _ 22 Metamorphism of limestone _________________ _ Upper unit ____________________________ _ 46 22 Recrystallization to marble _____________ _ 46 Owens Valley formation ____________________ _ 24 Dolomitization ________________________ _ Lower unit. ___________________________ _ 47 24 Alteration to calc-hornfels, calc-silicate Middle unit ___________________________ _ 27 rock, and tactite _____________________ _ Upper unit ____________________________ _ 47 28 Alteration to feldspathic rock ___________ _ 50 Undifferentin.ted Paleozoic silicated limestone ______ _ 28 Alteration to amphibolite _______________ _ G.neiss. _______________________________________ _ 50 28 Geologic history ___________________________________ _ Mesozoic rocks ____________ -.- __________________ - ___ _ 51 28 Ore deposits _______________________________________ _ Intrusive rocks. _______________________________ _ 28 52 History and production _________________________ _ Biotite-hornblende-quartz monzonite _________ _ 29 52 Lead-silver-zinc deposits ________________________ _ Leucocratic quartz monzonite. ______________ _ 31 55 Distribution ______________________________ _ Aplite and leucogmnite _____________________ _ 31 55 Character of ore ___________________________ _ Dikes·----------------------------------------- 32 55 Alt.ered andesite porphyry dikes. ____________ _ 32 Forms of ore bodies. _______________________ _ 56 Diorite ___________ - __________ - __ - __ - __ ----- 32 Bedded deposits _______________________ _ 56 Cenozoic rocks. ____________________________________ _ 33 Irregular replacement ore bodies _________ _ 56 Vein deposits __________________________ _ Pliocene (?) _____________________ --------------- 33 56 Pyroclastic rocks ___________________________ _ 33 Ore bodies in flat-lying fractures _________ _ 56 Lower pyroclastic unit __________________ _ 33 Ore controls _______________________________ _ 57 Upper pyroclastic unit __________________ _ 34 Nearness to intrusive contacts ___________ _ 57 Andesite ____________________ --------------- 35 Relationship of ore deposits to s~ratigraphy _ 57 Old fanglomerate from the lnyo Mountains. __ _ 36 Relationship of ore to folds. ____________ _ 57 Coso formation ____________________________ _ 36 Relationship of ore to faults _____________ _ 58 Ill IV CONTENTS Page Page Ore deposits-Continued Ore deposits-Continued Lead-silver-zinc deposits-Continued Tungsten deposits _____________________________ _ 76 ~ineralogy _______________________________ _ 58 Distribution _______________________________ _ 76 Hypogene minerals _____________________ _ 59 Previous work and acknowledgments _________ _ 76 Ore and sulfide minerals ____________ _ 59 Deposits in the Darwin district ______________ _ Gangue minerals ___________________ _ 62 76 Supergene minerals ____________________ _ 63 Geology~------------------------------ 76 Ore bodies ____________________________ _ 77 Sulfide zone _______________________ _ 63 Grade ________________________________ _ Oxide zone ________________________ _ 63 77 Paragenesis ___________________________ _ Ore controls--~- _______________________ _ 77 64 ~ineralogy ___________________________ _ Primary zoning ________________ - ____ -- __ -_-- 77 66 Deposits in the Coso Range _________________ _ Oxidation and enrichment __________________ _ 66 79 Other deposits _________________________________ _ Classification and origin ____________________ _ 68 79 Darwin lead-silver-zinc district ______________ _ 69 Nonmetallic commodities ___________________________ _ 79 Geochemical prospecting ___ ._ ____________ _ 71 Steatite-grade talc _____________________________ _ 80 Future of the district ___________________ _ 72 Geology __________________________________ _ 80 Zinc Hill district ___________________________ _ 73 Talc ore bodies ____________________________ _ 80 Lee district _______________________________ _ Origin ____________________________________ _ 74 81 Deposits in the Inyo ~ountains and Talc City Chlorite deposits ______________________ .:. ________ _ 75 81 Hills------------------------------------ Literature cited ____________________________________ _ Santa Rosa mine ______________________ _ 75 81 Deposits in the Talc City Hills __________ _ 76 Index--------------------------------------------- 85 ILLUSTRATIONS [Plates are In pocket] PLATE 1. Geologic map and sections of the Darwin quadrangle Inyo County, Calif. 2. Geologic map of the Talc City' Hills. 3. Geologic map and sections of the Darwin mine area. 4. Map of part of 400 level and section of the 430-stope ore body of the Defiance workings. 5. Maps of the No. 6 and No. 10 levels of the Christmas Gift mine, showing localization of ore. 6. Map showing. distribution of total copper-lead-zinc from soil samples over th~ Defiance and Bernon workings of the .. : Darwin mine. 7. Map showing distribution of antimony, bismuth, and silver in residual soil over the Defiance-Bernon workings of the Darwin mine 8. Maps and section of upper workings of the Zinc Hill mine. 9. Geologic map and sections of the Main stope of the Silver Reid mine. 10. Geologic map of the Durham, Fernando, and St. Charles mines, Darwin district, Calif. Page FIGURE 1. Index map showing location of the Darwin quadrangle _____________ ,_____________________________________ 2 2. Index map sho.wing the location-of lnyo County lead-silver-zinc deposits__________________________________ 3 3. Simplified geologic map of the Darwin quadrangle showing the geologic setting of the ore deposits____________ 7 4. Photograph or'the Talc City Hills near the Viking mine showing the overturned Paleozoic section of the Pogonip group, Eureka quartzite, Ely Springs dolomite, and Hidden Valley dolomite_____________________________ 9 5. Lee Flat limestone viewed south from the Lee mine_____________________________________________________