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Geology and Beryllium Deposits of the Lake George (Or Badger Flats) Beryllium Area, Park and Jefferson

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Geology and Beryllium Deposits of the Lake George (Or Badger Flats) Beryllium Area, Park and Jefferson Geology and Beryllium Deposits of the Lake George (or Badger Flats) Beryllium Area, Park and Jefferson t:-1 g Counties, Colorado ~s:p ~ I> li:tl ~ GEOLOGICAL SURVEY PROFESSIONAL PAPER 608-A g ~ ! e.Q qs. e. co ~ ~ ~ Q I ~ 4· e~- .•I ""'t1 ~., ~ 0 00 ~ Geology and Beryllium Deposits of the Lake George (or Badger Flats) Beryllium Area, Park and Jefferson Counties, Colorado By C. C. HAWLEY GEOLOGY AND ORE DEPOSITS OF THE SOUTHERN TARRYALL REGION PARK AND JEFFERSON COUNTIES, COLORADO GEOLOGICAL SURVEY PROFESSIONAL PAPER 608-A A study of the nonpegmatitic beryllium deposits, with special emphasis on their association with the late Precambrian Redskin Granite UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. ·Government Printing Office Washington, D.C. · 20402 Page Page Abstract------------------------------------------- A1 Ore deposit-Continued Introduction ______________________________________ _ 1 Mineralogy-Continued General geology ___________________________________ _ 2 Ore minerals-Continued Precambrian rocks~ ____ ~ _______________________ _ 2 Silicates-beryl, bertrandite, and euclase __ A17 Idaho Springs Formation ___________________ _ 3 Tungstates ____________________________ _ 19 Amphibolite and hornblendite _______________ _ 3 Gangue minerals _________________________ _ 19 Boulder Creek{?) Granodiorite ______________ _ 3 Halides _______________________________ _ 19 Silver Plume(?) Granite ____________________ _ 3 20 SilicatesCarbonates----------------------~----- ______________________________ _ Pikes Peak Granite and associated rocks _____ _ 4 20 Gabbro and monzonite _________________ _ 4 Other minerals _______________________ _ 21 Pikes Peak Granite ____________________ _ 4 Paragenetic sequence _________________________ _ 21 Redskin Granite _______________________ _ 5 Origin of the beryllium deposits _________________ _ 22 Tertiary(?) and Quatern~ry deposits _____________ _ 6 Greisen areas and representative mines _______________ _ 23 Structure-------------------------------------- 6 Boomer mine area _____________________________ _ 23 Old folds and metamorphic structures ________ _ 7 Rocks ____________________________________ _ 23 Younger folds and metamorphic structures ____ _ 7 Structure _________________________________ _ 24 Greisen ___________________________________ _ FauUs------------------------------------~ 7 24 Geologic history _______________________________ _ 8 Boomer mine ______________________________ _ 24 Ore deposits ________ ~ ______________________________ _ 8 J & Sgroup _______________________________ _ 28 Greisen---------------------------------------- 9 China Wall area _______________________________ _ 30 Distribution of beryllium deposits and greisen ___ . __ 9 Mary Lee mine area ___________________________ _ 31 Distribution of beryllium deposits relative to Mary Lee mine ____________________________ _ 31 that of the Redskin Granite ___________ . __ _ 9 Redskin Gulch area ____________________________ _ 33 Distribution of beryllium deposits relative to Redskin mine _____________________________ _ 33 that of other rock units ___________________ _ 10 Black Prince mine _________________________ _ 35 Distribution of greisens _____________________ _ 10 Tappan Mountain area_______________ . _________ _ 35 General character of the beryllium ores ___________ _ 10 Summary of economic aspects of the deposits and sug- Form, size, and structural relations of the beryllium gestions for prospecting ___________________________ _ 37 ores ____________________________________ _ 11 General guides to ore _____ ~---------------------- 37 Greisen pipes ______________________________ _ 12 Boomer mine area _____________________________ _ 39 Vein deposits ______________________________ _ 13 China Wall area _______________________________ _ 40 Deposits localized by favorably oriented rock Mary Lee mine area _________________/(_ ________ _ 40 units and contacts _______________________ - 13 Redskin Gulch area and other parts of the Redskin ~ineralogy ___________________________________ _ 1.6 stock _______________________________________ _ 40 Ore minerals ______________________________ _ 16 Tappan Mountain area _________________________ _ 41 Sulfides _______________________________ _ 16 Other areas ___________________________________ _ 41 Oxides ________________________________ _ 16 References cited ___________________________________ _ 41 Index---------------------------------~----------- 43 III IV CONTENTS ILLUSTRATIONS [Plates are in pocket] PLATE 1. Geologic map and sections of the Lake George (or Badger Flats) beryllium area. 2. Map of fluorite deposits and beryllium- and greisen-rich areas. 3. Geologic map and sections of the Boomer mine area. 4. Geologic maps and sections of the Boomer. mine. Page FIGURE 1. Index map showing location of the Lake George (or Badger Flats) beryllium area_-_-______________________ A2 2. Sketch of beryllium-bearing greisen pipe, Boomer mine, showing arsenopyrite "footwall gutter"______________ 11 3. Diagrammatic view of the Minerva J and Redskin greisen pipes__________________________________________ 12 4. Photograph of south.edge of main Redskin pipe________________________________________________________ 12 5. Maps showing relations of greisen pipes to,fractures_____________________________________________________ 14 6. Map of part of the 8,516-foot level, Boomer mine, showing northeast-striking veins and ore along granite-aplite contact---------------------------------------------------------------------------------------- 15 7. Map of the Boomer vein, 8,533-foot level, Boomer mine_________________________________________________ 15 8. Photomicrograph of quartz-bertrandite-muscovite ore, Minerva N prospect________________________________ 19 9. Geologic maps and section of the J & S group mines _______ --- ___ - _____________ ---______________________ 29 10. Geologic map of the China Wall area------------------------------------------------------------------ 30 11. Geologic map of the Mary Lee mine area _________________ -----_- _____________ ---_-____________________ 32 12. Geologic maps and section of the Mary Lee mine __________ - _____ -_- ___ -________________________________ 35 13. Geologic maps of the Redskin and Black Prince mine areas in the Redskin Gulch area_____________________ 3 7 14. Geologic map of the Tappan Mountain area ___ ------_---_---_-------_---_---_- _____ -__________________ 39 TABLES Page TABLE 1. Average modal analyses of coarse-grained inequigranular Pikes Peak Granite_______________________________ A5 2. Average modal composition of the main facies of the Redskin Granite_____________________________________ 6 3. Spectrographic analyses of beryl from the Boomer mine_________________________________________________ 18 4. Semiquantitative spectrographic analyses of wolframite from the Boomer and Mary Lee mines_______________ 19 5. Semiquantitative spectrographic analyses of fluorite from the Boomer mine________________________________ 20 6. Analyses of samples from the Boomer mine____________________________________________________________ 25 7. Spectrographic analyses of samples from the J & S group of the Boomer mine area__________________________ 28 8. Semiquantitative spectrographic analyses of samples from the Mary Lee mine______________________________ 33 9. Semiquantitative spectrographic analyses of samples from Redskin Gulch area ____________________________ . 38 GEOLOGY AND ORE DEPOSITS OF THE SOUTHERN TARRYALL REGION PARK AND jEFFERSON COUNTIES, COLORADO GEOLOGY AND BERYLLIUM DEPOSITS OF THE LAKE GEORGE (OR BADGER FLATS) BERYLLIUM AREA PARK AND JEFFERSON COUNTIES, COLORADO By c. c. HAWLEY ABSTRACT amounts of the beryllium occurs in euclase. The beryllium deposits locally contain arsenopyrite, wolframite, molybdenite, The Lal\:e George (or Badger Flats) beryllium area is a ter­ galena, and dark sphalerite, and these minerals and other sul­ rane of Precambrian rocks on tlie southwest side of the Front fides and oxides are locally concentrated in small ore shoots Range in Colorado. Its southeastern and southwestern parts are near beryllium deposits or in greisenized rocks nearly free of underlain mainly IJy the metasedimentary Idaho Springs Forma­ beryllium. The gangue of most deposits is formed by the typical tion, the metaigneous Boulder Creek ( ?) Granodiorite, and greisen minerals. the Silver Plume( ·n Granite. The northern and central parts of the area are underlain principally by the Pikes Peak and Though the deposition of ore minerals and the formation of Redsldn Granites. Locally the Precambrian rocks are masked greisens were nearly contemporaneous, the ore minerals are by thin tuffs and boulder deposits of Tertiary ( ? ) age and by somewhat younger than the greisens. Quartz, muscovite, and colluvium and alluvium of Quaternary age. fluorite, which form the bulk of the greisens, also occur with The oldest rocks-Idaho Springs Formation, amphi·bolite and the ore minerals and were deposited during a long period of time.. hornblendite, and Boulder Creek ( ?) Granodiorite-were in-· The beryllium deposits and associated greisen are closely volved in a period of plastic deformation during which a major related genetically to the Redskin Granite, as shown by chrono­ north-northeast-trending fold, the Round Mountain syncline, logie and chemical similarities and spatial association.
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