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Geology of the Basin Quadrangle Jefferson, Lewis and Clark, and Powell Counties, Montana

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Geology of the Basin Quadrangle Jefferson, Lewis and Clark, and Powell Counties, Montana Geology of the Basin Quadrangle Jefferson, Lewis and Clark, and Powell Counties, Montana By EDWARD T. RUPPEL GEOLOGICAL SURVEY BULLETIN 1151 A descriptive report of an area along the west margin of the Boulder batholith UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U.S. Geological Survey Library has cataloged this publication as follows : Ruppel, Edward Thompson, 1925- Geology of the Basin quadrangle, Jefferson, Leis and Clark, and Powell Counties, Montana. Washington, U.S. Govt. Print. Off., 1963. 121 p. illus., maps (1 col.) diagrs., tables. 24 cm. (U.S. Geological Survey. Bulletin 1151) Part of illustrative matter folded in pocket. Bibliography: p. 119-121. 1. Geology Montana Basin quadrangle. 2. Mines and mineral re­ sources Montana Basin quadrangle. I. Title: Basin quadrangle. Montana. (Series) For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 , CONTENTS Page Abstract-----...---..---------------------------------------------- 1 Introduction._ ____________________________________________________ 2 Location and access___-___--___-__-___---__-__--___--____--____ 2 Topography and drainage._____________________________________ 3 Vegetation__________________ ________________________________ 4 Previous work.-_______________________________________________ 4 Present work and acknowledgments--.._____.___-___-____.___-___ 5 Geology._______-_-______-________________-______-__----__--_-____ 6 Sedimentary rocks.-.--_____--_-_____________--------__---_____ 8 Morrison formation ________________________________________ 8 Kootenai formation ________________________________________ 8 Colorado formation ________________________________________ 9 Elkhorn Mountains volcanics----------------------------------- 9 Stratigraphic relations___.__.______________-___-__-_--.___ 10 Rock types _______________________________________________ 14 Welded tuff____-...-__...-__-...__-._-._.---___-.-.._. 14 Tuff and lapilli tuff _-----_-__...._____-_...____----..-_ 17 Breccia___-______..__-_______--.__.__:_____-__--_-____ 18 Volcanic sedimentary rocks_____.____-_-__.__-__-____. __ 19 Andesitic intrusive rocks__ _____________________________ 20 Basalt____----------_-_--_-_-----__-_-------------__-_ 20 Basaltic intrusive rocks_______________________________ 21 Age relations of basalt__ _______________________________ 21 Batholithic rocks______________________________________________ 22 Classification of batholithic rocks_-_---__--_--_---------_-___' 28 Inclusions _________________________________________________ 29 Petrography._____________________________________________ 30 Early-stage batholithic rocks...------------------------- 32 Butte quartz monzonite ________________________________ 33 Coarse-grained rocks...____________________________ 33 Medium-grained rocks _____________________________ 33 Fine-grained rocks.._______________________________ 35 Late-stage batholithic rocks_-------------------------- 36 Emplacement of the batholithic rocks------.---.---.--------- 36 Is the Boulder batholith a laccolith?_ ____________________ 40 Metamorphism. _ _____________._._.__..___:-___-___________ 40 Late magmatic alteration.__________________________________ 42 Age of quartz monzonite and related rocks.-----.------------- 43 Tertiary volcanic rocks_________________________________________ 44 Lowland Creek volcanics-----___-_--._.__---------------_-- 44 Petrography __________________________________________ 46 Volcanic sedimentary rocks_-___-_--------_--_---_-_ 46 Tuff and lapilli tuff ________________________________ 47 Welded tuff_______________.______.________________ 50 Flow rocks._______________________________________ 50 Intrusive rocks.___________________________________ 51 in IV CONTENTS Geology Continued Tertilary volcanic rocks Continued Page Rhyolite_________._______--.-_-.-----.-----_-__----_---_ 52 Petrography _______.-___-_____---_-__-__-_-___----__-_' 54 Flow rocks______________---_-_-_---_____---___-_ 54 Flow breccias. _________-_-_---_--_---_-_-_- --_-_-_ 55 Basal glasses._____________------__---_____---_-_-_ 56 Welded tuff.________________._____---..__--_-.__-_ 56 Lapilli tuff and tuff.________________________________ 57 Intrusive rocks.____--_-_-_-------_-----__------___ 57 Tertiary prevolcanism surfaces ______________________________ 57 Age relations of quartz latite and rhyolite____-_______---__--_ 58 Surficial geology.__________-_-----------------------_---------- 60 Gravel veneering strath terraces..__________________--------- 60 Glacial deposits.____-__-___-__-----_-----_----__---------- 61 Mass-wasting deposits_______---___-----_____-___--------- 63 Creep-and-solifluction deposits_________________-----_.-- 63 Protalus rampart and rock stream deposits_______________ 64 Talus deposits.----------------------.----------------- 65 Landslide deposits.____________________________________ 65 Bog and swamp deposits._--____-__--____-_________---___-_ 65 Structural geology.____________________________________________ 65 Folding in Elkhorn Mountains volcanics._____________________ 67 Joints. -----_----___-_.----------------__.-_____---------_ 68 Lineaments, breccia pipes, and shear zones_________________ 72 Faults.-----__--.._-____-------_-_--..___.-.----.-.-.-. 75 East-trending fault zones.______________________________ 75 North-trending faults._________________________________ 77 N. 20° E.-trending faults_______________________________ 79 Northeast- and northwest-trending faults._--_-_-_-------- 81 Thrust faults______.__________----------------------- 82 Faults near Basin______-------_--__--_.-_-------------- 82 Summary of evolution of landforms._____________________-_-_---- 83 Mineral deposits_________________________________________________ 85 History of mining.____________________________________________ 86 Metallic mineral deposits._-----_--___._________________________ 88 Classification__ _.________________________________________ 88 Disseminated deposits of auriferous pyrite____________________ 88 Deposits in quartz veins___ _______________________________ 89 Secondary enrichment__.____________________________________ 92 Placer deposits.___________________________________________ 92 Gold-bearing placer deposits ____________________________ 92 Tin-bearing placer deposits _____________________________ 93 Nonmetallic deposits.____-____--__-________-_________------_--- 95 Mines ________________________________________________________ 97 Ada mine_________________________________________________ 97 Armstrong mine.__________________________________________ 98 Aurora mine______________________________________________ 98 Beatrice mine._______________________'_____________________ 99 Boulder mine_____________________________________________ 100 Buckeye mine_____________--___------___--_--_---------- 101 CONTENTS Mineral deposits Continued Mines Continued Page Bullion mine._____________________________________________ 101 Crystal, St. Lawrence, and Sparkling Water mines (Crystal group)------------------_------------------------_--.-- Hope, Katie, and Katie Extension mines (Jib group)..-.------_ Iron Mountain iron deposit.._______________________________ Josephine mine.-___-___.__--___.-_-_______-______-_-____._ Justice-Clementh (Clemantha) mines_______________________ Lady Hennessey mine-_--____---_--------------___---___-_- Lady Leith-Cady Leith mines.._____________________________ Lotta tunnel._____________________________________________ Monte Cristo mine ________________________________________ Morning mine___-____---___-----_-_-_-_____--____-----__-- Porphyry Dike, Paupers Dream, and VenuS mines....---.-..-. Solar mine___--_-__-_---__----____-_--___-__-____---______ Sylvan mine._---__---_-_-_-_--___--------__--_-----_---_- Uncle Sam mine_-___-----------___-__-___-__-_--___-_-____ Vindicator mine--__-----_------^------_-------------_----- Winters Camp and Morning Star mine_--_-_-__--_---_---__-- References cited..__________-___-_____-_---__---__-_---__-__---___- ILLUSTRATIONS [Plates are in pocket] PLATE 1. Geologic map and sections of the Basin quadrangle. 2. Geologic map showing generalized distribution of types of quartz monzonite within the Boulder batholith, Basin quadrangle. 3. Generalized map of Oligocene prevolcanic topography. 4. Generalized map of Miocene(?)-Pliocene(?) prevolcanic topography. 5. Structure map of the Basin quadrangle. 6. Map of Bullion mine. 7. Plan and vertical longitudinal projection, Jib mine group. Page FIGURE 1. Index map showing location of Basin quadrangle. _____________ 2 2. Quantitative mineralogical classification of igneous rocks. 7 3. Thin-section modes of rocks of the Boulder batholith---------- 23 4. Comparison of oxides in rocks of the Boulder batholith, Basin quadrangle ____________________________^______________ 24 5. Outcrops of quartz latitic volcanic conglomerate west of Mor­ mon Gulch____________-_-_____-__-_____--_____--_____. 48 6. Large spherulite in rhyolite flow rocks east of the Josephine mine... _____-_-____-____---__._-_-______-__.___--_-__. 55 VI CONTENTS TABLES [Tables 5 and 6 are in pocket] Page TABLE 1. Interpretation of stratigraphic relations in the Elkhorn Moun­ tains volcanics-________________________________________ 12 2. Chemical and spectrographic analyses of welded tuff of the Elkhorn Mountains volcanics____________________________ 16 3. Chemical and spectrographic analyses of Boulder batholith rocks
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