Ore Deposits of the· Kokomo-Tenmile District, Colorado By M. H. BERGENDAHL and A. H. KOSCHMANN .. I GEOLOGICAL SURVEY PROFESSIONAL PAPER 652 Prepared in cooperation with the Colorado Mining Industrial Development Board .. UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971 1\ UNITED STATES DEPARTMENT OF THE INTERIOR \ ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY W. A. Radlinski, Acting Director Library of Con~&ress cataloll·card No. 73-611465 ..,_ For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page 1 Ore deposits-Continued Page Abstract------------------------------------------- 2 Zoning of ore deposits___________________________ 27 Introduction--------------------~------------------ Location and accessibility _______________________ _ 2 llypogene ore minerals__________________________ 29 Culture_______________________________________ _ 3 Pyrite __ -_-________________________________ 30 Relief, physical features, and drainage ____________ _ 3 Sphalerite__________________________________ 30 Climate ______________________________________ _ 3 Pyrrhotite_________________________________ 32 Fieldwork and acknowledgments _________________ _ 4 Marcasite__________________________________ 32 4 Galena____________________________________ 34 Production----------------------------------------- llistory ___________________________________________ _ 5 Chalcopyrite_______________________________ 34 Previous studies ___________________________________ _ 8 Arsenopyrite_______________________________ 34: 8 Molybdenite_______________________________ 34: General geologY------------------------------------ Precambrian rocks _____________________________ _ 8 Tetrahedrite______ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 8 Enargite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 Granulite---------------------------------- 9 Pearceite (?) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 Banded gneiss _____________________________ _ • Migmatite ________________________________ _ 9 Gold-------------------------------------- 35 Pink migmatite ____________________________ _ 10 Magnetite--------------------------------- 36 11 Hematite ____________ - ______________ - ___ -__ 36 Biotite-muscovite quartz monzonite __________ _ Gneissic granite ___________________________ _ 11 Fluorite___________________________________ 36 11 Rhodochrosite _______________________ -______ 36 Pegmatites and other dikelike rocks __________ _ Paleozoic rocks ________________________________ _ 12 Supergene minerals----------------------------- 36 Minturn Formation ________________________ _ 12 Covellite_-_-- ___ - _- __ -- ___ - ___ - ___ - _ _ _ _ _ _ _ _ 36 Maroon Formation _________________________ _ 12 Cerussite_- ___ --- ___ - _____ -_-_-- __ --- ___ --_ 36 Volcanic rocks _____________________________ _ 14 Smithsonite ____ - __________ - ___ - ___ - _- ___ -- _ 36 Tertiary rocks _________________________________ _ 14 Malachite and azurite_______________________ 37 Elk Mountain Porphyry ____________________ _ 14 Anglesite ______ --- ___ - ___ --- _- _-- __ --- ___ -- _ 37 14 Limonite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 7 Porphyritic quartz monzonite _______________ _ Quail Porphyry ____________________________ _ 15 Pyrolusite and psilomelane___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 37 Quartz monzonite __________________________ _ 15 Silver_____________________________________ 37 Lincoln PorphyrY--------------------------- 15 Distribution of minor elements in sulfide minerals___ 37 Chalk Mountain Rhyolite ___________________ _ 15 Gangue minerals________________________________ 39 Quaternary deposits ____________________________ _ 15 Paragenesis of the hypogene minerals_- __ - _____ -__ 39 15 Early stage________________________________ 39 Structure------------------------------------ 16 Intermediate stage__________________________ 39 Faults----------------------------------------- Mosquito fault ____________________________ _ 16 Late stage_________________________________ 4:0 Northeast-trending faults ___________________ _ 16 Temperature of deposition_______________________ 40 Northwest-trending faults ___________________ _ 16 Genesis of the ores------------------------------ 4:0 Other faults _______________________________ _ 17 Mine descriptions----------------------------------- 41 Periods of deformation _________________________ _ 17 Wilfley-Kimberly mine __ --------________________ 41 17 History and production______________________ 41 Folds------------------------------------ Folds in Precambrian rocks _________________ _ 20 Characteristics of the ore bodies______________ 4:3 Folds in Paleozoic rocks ____________________ _ 20 Robinson Consolidated mine, Eldorado and Wilson Unconformities ____________ :. ___________________ _ 20 mines, Felicia Grace mine, and Champion (New Ore deposits _______________________________________ _ 21 York) mine---------------------------------- 43 Replacement deposits ________________ ~ _________ _ 21 Introduction_______________________________ 43 Structural relations ________________________ _ 22 History ___ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 43 Size and shape of ore bodies _________________ _ 23 Production_________________________________ 44: Varieties of ore ____________________________ _ 23 Characteristics of ore bodies________________ _ _ 45 W allrock alteration ________________________ _ 24 Grade of ore ________________________ -______ 46 Depth of ore ______________________________ _ 24 Workings---------------------------------- 46 Grade of ore ______________________________ _ 25 Victory-Lucky Strike mine_______________________ 4:7 Vein deposits __________________________________ _ 25 · History and production______________________ 4:7 Carbonate veins ___________________________ _ 25 Geology, ore bodies, and workings_ _ _ _ _ _ _ _ _ _ _ _ 4 7 Pyrite-sphalerite-galena veins ________________ _ 26 Suggestions for prospecting and future of the district____ 4:7 Ore bodies--------------------------------- 26 References cited____________________________________ 48 Magnetite-garnet-molybdenite deposits ___________ _ 26 IndeX--------------------------------------------- 51 III IV CONTENTS ILLUSTRATIONS Page PLATE 1. Geologic map of Kokomo-Tenmile district------------------------------------------------------ In pocket 2. Underground geologic maps of the Wilfley and Kimberly, Robinson, and Lucky Strike-Victory mines ____ In pocket FIGURE 1. Index map of Kokomo-Tenmile district ___________________________________________________________ _ 2 2. Photograph of town of Kokomo _______________________________________________ .. _________________ _ 3 3-8. Photographs: 3. Banded gneiss cut by pegmatite ___________________________________ ·----------------------- 9 4. Contact of granulite and banded gneiss ____________________________________________________ _ 9 5. Boudinage structure in banded gneiss ______________________________________________________ _ 10 6. Migmatite, showing typical wavy foliation _________________________________________________ _ 10 7. Migmatite, showing contorted layering_--------- _______ --------- ______ ----------- __________ _ 11 .. 8. Southern part of Tenmile Range __________________________________________________________ _ 18 9. Sketch of generalized plan of ore bodies in middle part, White Quail Limestone Member _______________ _ 22 10. Diagrammatic sketch of section of typical replacement deposit ______________________________________ _ 23 11-13. Photographs: 11. Polished slab of sulfide ore ______________________________________________________________ _ 24 12. Brecciated limestone ____________________________________________________________________ _ 24 13. Solid galena ___________________________________________________________________________ _ 24 14. Map of Kokomo-Tenmile district showing areas of garnet and epidote alteration ________________________ _ 28 • 15. Photomicrographs of polished sections ____________________________________________________________ _ 31 16. Sketch of univariant curve for the reaction FeS2~Fet-zS-------------------------------------------- 32 17. Sketch of phases in Fe-S system---------------.--------------------------------------------------- 32 18. Photomicrographs of polished sections from the Michigan-Snowbank, Triangle, and Lucky Strike mines __ 33 19. Photomicrographs of polished sections from the Queen of the West and Gold Crest mines and from a prospect in Cresson Gulch--------------------------------------------------------------------------- 35 20. Sketch of sequence of deposition of major minerals of the ore der.osits ________________________________ _ 39 21. Map of outlines of mine workings and ore bodies--------------------------------------------------- 42 TABLES Page TABLE 1. Production of the Kokomo-Tenmile district, 1905-65------------------------------------------------ 5 2. Paleozoic sedimentary rocks in the Kokomo-Tenmile district _____________________________________ ---- 13 3. Chemical analyses (weight percent) of Tertiary intrusive rocks, Kokomo-Tenmile district_ _____________ -- 14 4. Average grade of ore from some of the major mines, computed from total production from 1902 to 1950.- _ 25 5. Varieties of garnet from the Jacque Peak-Tucker Mountain-Copper Mountain area _______ -------------- 27 6. Primary and secondary minerals of the ore deposits, Kokomo-Tenmile district ______________________