DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR BuiiIiETIN 574 MINING DISTRICTS OF THE DILLON QUADRANGLE, MONTANA AND ADJACENT AREAS BY ALEXANDER N. WINCHELL WASHINGTON GOVERNMENT PRINTING OFFICE 1914 CONTENTS. Introduction.. .\.......................................................... 11 Geography................................................................. 11 Location and area ...........;........................................ 11 Topography........................................................... 12 Mining districts....................................................... 14 Literature................................................................ 17 Mining development. ...................... .. - - ' - ----- 18 Discovery.....................;....................................... 18 Placer mining....... ~................................................. 19 Dredging.............................................................. 19 Deep mines. ........................................................... 20 Present status of mining .....:.......................................... 22 Stratigraphic and areal geology..............,...........'................... 23 Sequence of the rocks.................................................. 23 Quaternary system..........................................'............ 24 Recent series...... '. ............................................... 24 Pleistocene series................................................... 24 Tertiary system....................................................... 24 Cretaceous system..................................................... 25 Jurassic and Triassic systems........................................... 26 Carboniferous system.................................................. 26 Permian. (?) series...............................:.................. 26 Pennsylvanian (?) series........................................'.... 26 Massissippian series................................................ 27 Devonian system....................................................... 27 Silurian (?) to Cambrian rocks.......................................... 27 Algonkian system...................................................... 28 Belt series........................................................ 28 Cherry Creek group.................................................. 29 Archean (?) system..................................................... 29 Igneous rocks........................................ 4................. 29 Structure.. ................................................................ 30 Petrography.............................................................. 30 Plutonic rocks......................................................... 30 Granite............................................................. 30 Tonalite:......-..........................-........................ 31 Granodiorite...................................................... 32 Quartz monzonite................................................. 33 Diorite.................:.:.....................................,.. 37 Gabbro............................................................. 38 . Pyroxenite..............................1......................... 38 Peridotite......................................................... 39 3 4 - CONTENTS. Petrography Continued. Page. Hypabyssal or dike rocks.............................................. 40 Quartz monzonite porphyry.......................................... 40 Aplite......................;......!.:............................ 40 Aplite porphyry.................................................... 41 Pegmatite........................................................ 41 Alkaliaplite. ...................................................... 42 Minette............................................................ 42 Bostonite...............................:.......................... 42 Plagiaplite........... ; ............................................. 42 Tonalite aplite.................................................... 43 Quartz monzonite aplite- -...............................'...-...... .43 Volcanic rocks......................................................... 43 Rhyolite.......................................................... 43 Trachyte......................................................... 45 Dacite............................................................ 45 Quartz latite...................................................... 46 Andesite........................................................... 46 Latite.............'......................................:........ 49 Auganite......................................................... 49 Basalt............................................................. 50 Olivine trachydolerite.............................................. 51 Economic geology.......................................................... 51 Introduction.......................................................... 51 Ore deposits ... '. ..................................................... 52 Mineralogy......................................................... 52 Origin ............'................,............................... 55 Age.............................................................. 56 Age of country rock.................................................... 56 Mining districts............................................................ 57 Alder Gulch district.................................................... 57 Location.......................................................... 57 History. ....'. ...................................................... 57 Geology........................................................... 57 Placer deposits................................................... 58 Dredging......................................................._ 59 Production........................................................ Utopia (Birch Creek) district........................................... "Location.......................................................... History.................;........................... ..............; Geology........................................................... Ore deposits ...........'.............. ............................. Copper...................................................... Iron. ........................................................ ' Origin of ore deposits.............................................. Production.......... I............................................. Argenta district........................................................ Location.......................................................... History..............,.............;............................... Geology............................................................ Ore deposits. ..................................................'..- Origin of ore deposits............................................... Production....................................................... CONTENTS. 5 Mining districts Continued. Page. Blue Wing district....................................... '. ............. 69 Location.......................................................... 69 History............................................................ 69 Geology........................................................... 69 Ore deposits....................................................... 71 Origin of ore deposits............................................... 72 ' Production ........................................................ 72 Bannock district....................................................... 72 Location............................................................ 72 History............................................................ 73 Geology..................:...........-..........--...-............. 73 Ore deposits....................................................... 74 Production......................................................... 75 Outlying mines in Beaverhead County.................................. 76 Polaris district.................................................... 76 Bald Mountain district............................................. 76 Bloody Dick Creek.. ..............................-.----- -- - - 76 Jahnke mine ..................................................... 77 Ajax mine........................................................ 78 Vipond district....................................................... 78 Location:.... 1.................................................... 78 History.......................................................'.... 78 Geology and ore deposits.......................................... 78 Bryant (Hecla) district................................................ 79 Location.......................................................... 79 History............................................................ 80 Geology............................................................ 80 Ore deposits................................. r ..................... 82 Origin of ore deposits............................................... 84 Production........................................................ 86 Highland and Moose Creek districts..................................... 87 Location.......................................................... 87 Geology........................................................... 87 Petrography............... ...................................... 88 Ore deposits............................................1.........