Geology and Mineral Deposits of the Poncha Springs NE Quadrangle, Chaffee County,Colorado
Total Page：16
File Type：pdf, Size：1020Kb
Geology and Mineral Deposits of the Poncha Springs NE Quadrangle, Chaffee County,Colorado By RALPH E. VAN ALSTINE With a section on Fluorspar Mines and Prospects By RALPH E. VAN ALSTINE and DOAK C. COX GEOLOGICAL SURVEY PROFESSIONAL PAPER 626 Prepared in cooperation with the Colorado State Mining Industrial Development Board UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress catalog-card: No. 70-602625 For sale by the Superintendent of Docume!lts, U:S. Government Printing Office Washington, "D.C. 20402 o/\ 7 2 3 6 56 3 0 9 -, CONTENTS Page Page Abstract __________________________________________ _ 1 Economic geology----- ________ ---------------------- 30 Introduction ______________________________________ _ 2 Fluorspar deposits _________ ---------------------- 30 Earlier reports _________________________________ _ 2 History of production and ownership _____ -_-_- 30 Field and laboratory work _____________________ _ 2 Localization and structure_- __ -- ___ ---------- 30 Acknowledgments ______________________________ _ 4 Mineralogy _______________________ --------- :n Settlement and climate _________________________ _ 4 Paragenesis __________ ----------_----------- 34 Terrain _______________________________________ _ 4 Wallrock alteration _________________ --_---_- 34 Geologic units _____________________________________ ·- 4 Associated thermal · fluoride waters and the solubility of CaF2- _______ - _- _____ --------- 34 Precambrian rocks _____________________________ _ 5 Origin ____________________________________ _ 36 Metamorphic rocks _________________________ _ 5 Grade, size, and resources _____________ '- ____ _ a7 Banded gneiss __________________ ·_______ _ 5 Suggestions for prospecting_- ________ --_---_- 38 Hornblende gneiss _____________________ _ 5 Origin ________________________________ _ 6 Fluorspar mines and prospects, by Ralph E. Van Alstine and Doak C. Cox _________ _ 38 Igneous rocks _____________________________ _ 6 Colorado-American mine ______________ -_- 38 Gneissic quartz monzonite ______________ _ 6 39 Tabular intrusive rocks _________________ _ 7 Delay adit and Lloyd shaft ____ --_-----_- Tertiary rocks _________________________________ _ Manganese Hill and Chimney Hill mines_- 41 9 Last Chance mine _________________ -_-_- 42 Rhyodacitic ash, volcanic mudflow deposit, and flow ____________________________________ _ Other fluorspar deposits ________ --------- 42 9 43 Rhyolitic ash-flow tuff ______________________ _ Deposits of other materials ____________ ----------- 11 43 Nathrop Volcanics _________________________ _ Copper prospect _______________ -_----------- 15 Gold _____________________________________ _ 44 Browns Canyon Formation _________________ _ 18 Gravel and sand __________________ - - - - - - - - - - 45 Dry Union Formation ______________________ _ 20 Peat deposit _____________________ ---------- 45 Quaternary deposits ____________________________ _ 22 Pegmatite minerals ______________ ----------- 45 Pleistocene deposits ________________________ _ 22 Pumice and perlite ________________ ---------- 46 Holocene deposits __________________________ _ 25 Quartzite deposits _________________ ---------- 46 Structural geology _________________________________ _ 25 Vermiculite deposit _______________ ---------- 47 Geomorphology ___________________________________ _ 28 References cit(:ld _______________________ - _----------- 47 Summary of geologic history ________________________ _ 29 IndeX------------------------------------~-------- 51 ILLUSTRATIONS [Plates are in pocket] PLATE 1. Geologic map of the Poncha Springs NE quadrangle. 2. Geologic map of the Colorado-American fluorspar mine, Browns Canyon district. 3. Geologic map of underground workings, Colorado-American fluorspar mine. 4. Longitudinal section showing workings along East Vein, Colorado-American fluorspar mine. 5. Geologic maps of the Manganese Hill and Chimney Hill fluorspar deposits. 6. Geologic maps and vertical longitudinal projection of workings, Last Chance fluorspar mine. Page FIGURE 1. Index map of south-central Colorado, showing location of Poncha Springs NE quadrangle_____________________ 3 2-10. Photographs: 2. Columnar jointing in welded tuff________________________________________________________________ 12 3. ·Pronounced layering in devitrified rhyolitic welded tuff _______________________________ -_----------- 12 4. View northwest toward Mount Princeton, showing Pleistocene gravel-covered surfaces __ -_------------- 22 5. View northwest from Arkansas River, showing main fault zone_____________________________________ 31 6. Fine-grained layered fluorite _________________________________________________________ -----:.----- · 32 7. Nodular fluorite __________________________________________________________________________ ----- 32 8. Breccia fragment of welded tuff coated by psilomelane and fluorite _________________ -_-_-_----------- 33 9. View northwest in open pit at Colorado-American fluorspar mine _____________________ --------------- 39 10. Geologic maps and section of the Delay adit and Lloyd shaft ____________________________ -_--------- 40 III IV CONTENTS TABLES Page TABLE 1. Chemical composition of gneissic quartz monzonite, Poncha Springs NE quadrangle______________________ 6 2. Norm and mode of gneissic quartz monzonite, Poncha Springs NE quadr-angle____________________________ 6 3. Chemical compositian and norm of rhyodacite porphyry, Poncha Springs NE quadrangle__________________ 10 4. Chemical compositions and norms of black vitrophyric welded tuff and devitrified welded tuffs, Chaffee and Park Counties ___________________________________________. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 5. Sample data for potassium-argon age determinations, black vitrophyric welded tuff, Chaffee County_________ 15 6. Chemical compositions and norms of obsidian pellets and perlite from R·uby Mountain, Chaffee County______ 16 7. Chemical analysis of spessartite garnet from Ruby Mountain, Chaffee County____________________________ 17 8. Chemical and semiquantitative spectrographic analyses, gray rhyolite flow, Ruby Mountain, Chaffee County_ 18 9. Sample data for potassium-argon age determinations, Nathrop Volcanic~, Chaffee County__________________ 18 10. Pleistocene deposits, Poncha Springs N E quadrangle, Chaffee County_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 23 11. Semiquantitative spectrographic analysis of manganese oxide, Alderman fluorspar deposit, Browns Canyon district, Chaffee County __________________________________________________________________ -.- _ _ 33 12. Analyses of alkaline thermal waters from Browns Canyon and Poncha Springs fluorspar districts, Chaffee CountY-------------------------------------------------------------------------------~----- 35 13. Analyses of alkaline, cold mine waters from western K~ntucky and St. Lawrence, Newfoundland, fluorspar districts------------------------------------------------------------------------------------ 35 14. Analyses of typical ores of the Browns Canyon fluorspar district________________________________________ 37 15. Estimated fluorspar resources, Browns Canyon district, Chaffee County, expressed as short tons of crude fluorspar------------------------------------------------------------------------------------ 38 16. Semiquantitative spectrographic analysis of aplitic gneiss, brecciated and veined by quartz and calcite ___ ..,____ 44 17. Gravel pits in the Poncha Springs NE quadrangle, Chaffee County_______________________________ 45 GEOLOGY AND MINERAL DEPOSITS OF THE PONCHA SPRINGS NE QUADRANGLE, .CHAFFEE COUNTY, COLORADO By RALPH E. vAN ALsTINE ABSTRACT mediately south, a sequence of nine gravel deposits was estab lished, five of Wisconsinan Age. and four older. A chevkinite The Poncha Springs NE quadrangle, which contains a major bearing rhyolitic volcanic ash in the thkd oldest gravel unit fluorspar district, is in the Arkansas Valley between the Sawatch may be the equivalent of the Pearlette Ash Member of the Sappa Range and the southward extension of the Park Range. Altitudes For:mation of late Kansan· age in Kansas and Nebraska. in the quadrangle lie between approximately 7,290 feet and Holocene deposits consist of alluvium, colluvium, talus, land 9,290 feet. slide debris, and peat. 'l'llie peat, determined to be less than 200 The geologic units mapped consist of Precambrian metamor years old by radiocarbon dating, contains excellently preserved phic and igneous rocks, Tertia·ry volcanic and sedimentary rock;s, pollen, and bison and horse bones. and unconsolidated Pleistocene and Holocene deposits. Pre The quadrangle is on the east :flank of the north-trending Sa cambrian hornblende gneiss and banded quartz-feldspar-'bioti.te watch anticline. The geologic ·Structure is widely varied and gneiss are intruded by a large mass of gneissic quartz monzo ranges from complex folds ~n the Precambriran rocks to a linear nite. Quartzite and silicated marble are interlayered with the fault trough of 'Tertia·ry age that parallels the Arkansas Valley. gneisses, which, together with other structural and mineralogic ·steeply dipping foliation in the Precambrian metamorphic rocks evidence, suggests ,that the metamorphic rocks were originally generally strikes northeast or east. The foliation in the gneis sediments. The gneissic quartz monzonite occupies a 1bout