UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY, £ W. C. Mendenhall, Director Bulletin 877 GEOLOGY AND ORE DEPOSITS OF THE BAYHORSE REGION CUSTER COUNTY, IDAHO BY CLYDE P. ROSS Prepared in cooperation with the IDAHO BUREAU OF MINES AND GEOLOGY UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1937 For sale by the Superintendent of Documents, Washington, D. C. ........ Price $1.00 CONTENTS Page Abstract-_____________-___-_____------_--,---_-_-_-___------.--__ I Introduction_______ _________________________________________ 2 Location._________---_-___-___---__--,---_---__ -___-._____ 2 Scope......_________________-_______________ 2 Acknowledgments____-_________-_ __-_-..---_-_-_-_-_---_-_-_-_- 5 Earlier work_____________________._ -_.._____-___-_-_-___-__ 5 History. _____________.-______--______..-___-____-__--_________ 5 Topography______ ____.._ ___, ________________ 6 Stratigraphy and petrology...______....______________ 8 General features_____________________-_____________-_-!___-____ 8 Cambrian (?) rocks__-___-____________---_-_-___-_-_-________ 12 Garden Creek phyllite.....__--_-___---__-__--_--_-______-- 12 Bayhorse dolomite.._____._-___-_-___-_____-___-___-______ 12 Ordovician rocks.______-______._________--.-_-_______-.____.._ 14 Ramshorn slate___________________________________________ . 14 Kiunikinic quartzite.______________________________________ 17 Saturday Mountain formation...___________________________ 18 Silurian rocks_______________________________________________ 22 Trail Creek formation...__________________________________ 22 Laketown dolomite-_-__-___-_______---_-___-___-____-_____ 23 Devonian rocks-__------__-_-_--_----_----_-------_---_--___- 25 Jefferson dolomite_-__-_____-_____----__-_-_-_-_-___--____ 25 Grand View dolomite_-___._._..__---.-_---___-__--____..-. 27 Mississippian rocks----_--________-_-_-_-_____________________ 29 Milligen formation. ______ _________________________________ 29 Brazer limestone___________________.______________________ 33 Pennsylvanian rocks.__________________________________________ 36 Wood River formation..___________________________________ 36 Heavy minerals as aids in stratigraphic correlation._______________ 39 Granitic rocks and related intrusions.___________________________ 43 Distribution and correlation._______________________________ 43 Character. _______________________________________________ 44 Quartz monzonite-_---___-_-___---_-_-__--___________- 44 Granodiorite_ _ ______________________________________ 45 Quartz diorite._______________________________________ 46 Gabbro...--__-_______---_____-.___-________________ 47 Aplitic rocks________________________________________ 47 Lamprophy re_ ________________________________________ .48 Age...____________________________._.__ 48 Chain's volcanics__,_-_.______________________________________ 49 Latite-andesite member_________.___-_.____________________ 50 Germer tuffaceous member..-.____________________________ 53 Basalt and related flows__________________________________ 58 Yankee Fork rhyolite member._____________________________ 59 Travertine----.-..--__---_---..--__..-._._________. 62 in Cr IV CONTENTS Stratigraphy and petrology Continued. Challis volcanics Continued. Page Hot springs______________________^_______________________ 64 Age of Challis volcanics___-_-______.__-_-_-----_----__... 65 Tertiary intrusive rocks_________-_____-________________________ 68 Intrusive basalt and augite andesite.________________________ 68 Biotite andesite dikes._____________________._______________ 68 Augite syenite_________---_________-___________________-__ 68 Age of Tertiary intrusives-___________--_--________-________ 68 Quaternary deposits--__________-_____-__-______________-______ 69 Early Pleistocene glacial deposits________________________ . 70 Older alluvium_________________________________________ 70 Younger alluvium_______________________________________ 72 Flood-plain alluvium_______________________________.______ 72 Structure.---_--_--_-______________________________________ 73 Deformation in Paleozoic rocks_______________________-__--__.__ 73 Anticline in Pahsimeroi Mountains___________________--_____ 73 Anticline near Lone Pine Peak___________________ ______ 75 Anticline near Bayhorse and Clayton________________________ 75 Deformation along the border of the batholith________________ 79 Relation between deformation and intrusion,_________________ 80 Tertiary deformation-_____-__-_______-_____-_-___-___-_-______ 82 Geomorphology____________-_________-_-_____-_________-_-_-______ 87 Pre-Challis surface--_-_---_-__-_--_---_-------_-------------_- 87 Post-Challis surface.__________________________________________ 89 Late Tertiary events-____________._____-_________-_---_-___-__ 91 Nebraskan (?) glaciation_____________________________________._ 93 Pleistocene stream terraces______________________-_-________-___ 95 Wisconsin glaciation____________________ ____ ___________ 96 Recent erosion_________________________________ __________ 97 Economic geology.___________ _____ _____________________ 99 Lodes_-_____.___-____.. _-_-__ - -- 101 Periods of mineralization________ __________________ 101 Irregular replacement deposits in Paleozoic calcareous rocks 102 Lodes on shear zones in the Paleozoic rocks __________________ 105 Lodes in granitic rock___________________________________ 110 Miscellaneous deposits._________-___---_-_---_-----------_- 111 Veins in the Challis volcanics____________-__-__-_-_-_---____ 112 Oxidation____________________... ___ 112 Enrichment-__________________________________________ 113 Outlook._______________________________ 115 The mines_________ 116 Bayhorse district..______.__________--__--__-__-_--_-_.._ 116 Good Hope mine.___________________________________ 116 Deposits near Garden Creek._________-_-_-_____-.-__ 116 Ramshorn mine._____.___-_______-___-.-_-__--_---__ 117 Skylark mine________________ _ __________ 122 Virginia Dare mine______________-______-_-_-_---____._ 125 Deposits along Juliette Creek.________________________ 125 Beardsley mine--___-______--____-____.___-._---__ _ 125 McGregor group_______-_-_____-___---_-_---__--_ .. 129 Kuna mine.____________________.____._---_-_-__.__ 132 Nameless mine._-_.__-_______-__-__-_-_-----_.-- __ 132 Riverview mine._____-___-___-_-_______-_----__---_- 132 CONTENTS Economic geology Continued. The mines Continued. Bayhorse district Continued. Page Turtle mine. __ . __ .. __ --...-._-_-.---__-----__-- 133 Last Chance mine... ------- ._ . 134 Mammoth mine. ___ _____----_-_--_---_-__--___--__- 135 Silver Bell mine _________________________ . 135 Williams, Rohlds, and Ernst mine. _ .. _ ....... 135 Sulphide mine.-. ____-_--___--____---_----_-_--___-._- 136 Mule Shoe mine. _ . __ _--___--___-_-_---_______-__-.. 136 Pedrino mjne____ ____---_-_______--------__----__-_--_ 136 Sadie claim.. _ .._-_..____.___-_..---_._-_-__--___--. 136 Compass mine_______. .___________-_--_-_-_-__-____..- 137 Clayton mine__._-_ __ ______._____------__-_---_-...- 137 Ella mine.---.-. __ _____ __ __ -. _ _-_.- _ _ - 138 Union-Companion mine_--________ _____________.-_.__-. 139 Red Bird niine... __ ...... ___ ... _ ....... _ ..... 139 South Butte mine __ _ ..-__ .. -_.. 143 Saturday Mountain group. ______.__________.__._.._.... 144 Dryden mine.-.. _ ... __ __ . ____ _._._--_..._. 145 Twin Apex mine. _-_-_------_-____----_---.-__---___-- 146 Bruno mine. ----_--..-_-___-___...-____---__---_____- 147 Buckskin mine. _. _ _______..______-._________..___..- 148 Rain-in-the-face mine. __ __-.-__---_-__---____-_.._..- 148 Silver Rule mine____. _.-__-_-._.__--___-___-_-_-___--. 148 Boulder Creek district--..-.---.-. -____---___.._______.___- 14& Badger claim. ._____._______..____.._._________.____.. 14& Quartz veins in the Challis volcanics__ __ _-___-__--____- 14& Livingston mine. ---___----_--___-----___-_.._--_--_-- 14? Little Livingston mine. _ ____-_--____-__--_-_-_-__-_-_ 151 Crater mine-____-_____. _-_-_-__..__.__.___._-_-..___- 152 Hermit mine----_-______-__-__--____-___-_______-_.-- 153 Molybdenite prospects_--___-----_---_-_-_--_______...- 153 Fuller and Baker prospect. __ _--___-___-.--___--_...-_ 154 Strawberry Basin mine--_-__-___--_-___--.-____. ...... 154 East Fork district. _ . ___-..-.......__ _ ...-_ _ .. 155 Aztec mine---__---_-_----___-_---___------_----.-__-- 155 Lucky Strike mine. --______________-_..___.-______.__. 155 Deertrail mine _ _._________.______._.____.___.._-._.__. 156 Mines in Washington Basin__. __._____.___._____._._... 156 Mines in Germania Basin______. _______________________ 157 Lodes near the head of Germania Creek.. __ ___________ 157 Index. ________ __ ______ ______________ ___________ _ _____ 159 ILLUSTRATIONS Page PLATE 1. Geologic map and structure sections of the Bayhorse region, Idaho __.-_---___-_____.____-___..-_____..__..____ In pocket 2. A, Outcrop of Ramshorn slate at the mouth of Wood Creek; B, Brazer limestone with chert bands along Broken Wagon Creek.__._....._______________......__.._............ 32 VI ILLUSTRATIONS Page PLATE 3. A, Disturbed Brazer limestone along the cut-off road between Pecks Canyon and the Mackay Highway; B, Dark quartz diorite intruding light-colored Wood River beds with apophyses along the bedding, about a mile west of Calkins Lake_...__--_-------___.__..-_________-____-______ 33 4. A, Polygonal-jointed andesite in sec. 27, T. 13 N., R. 19 E.; B, Coarse conglomerate at the base of the Germer member in Malm Gulch-...____._____.....--_.___.. 56 5. A, Distinctly bedded