TERRITORY OF AU- - ~C!PA#~~EUTOF -y - DEPARTMENT OF THE INTERIOR KETCHIKAN,ALASKA UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, D~ECTOR GEOLOGY AND ORE DEPOSITS 0 F COPPER MOUNTAIN AND KASAAN PENINSULA ALASKA BY CHARLES WILL WRIGHT WASHINGTON GOVERNMENT PRINTING OFFICE 1915 CONTENTS. Preface. by Alfred H . Brooks ............................................................................. Introduction ............................................................................................ Location of areaa described .......................................................................... Scope of report- .................................................................................... Surveys and explorations ........................................................................... Geologic maps ..................................................................................... Acknowledgments .................................................................................. Ketchikan district ..................................................................................... Topography ......................................................................................... General features.............................. .I.. ............................................... Mainland ...................................................................................... Prince of Wales Island ........................................................................... Climate ............................................................................................ Vegetation ......................................................................................... Commercial conditions .............................................................................. Production of copper ............................................................................... Geology ............................................................................................ General featmes................. r. ............................................. :................ Sedimentary rocks ................. .-............................................................. Paleowic strata ............................................................................ Mesowic strata ............................................................................. Tertiary strata .............................................................................. Recent deposits ............................................................................ Igneousrwks ................................................................................... Classes discriminated ....................................................................... Intrusives of the Coast Range ............................................................... General features ......................................................................... Contact features ........................................................................ Other intrusives ............................................................................. Extrusives ................................................................................. Structure ...................................................................................... Outline of geologic history ...................................................................... General dietribution of mineralization .................... :...................................... Copper Mountain area .................................................................................. Topogrsphy ......................................................................................... Geology ............................................................................................ General features ................................................................................. Sedimentary rocks ............................................................................... Schisb ..................................................................................... Limestones ................................................................................. Thickness and character ................................................................. Occurrence ............................................................................ Age ................................................................................... Structure .................. .... ....................................................... Metamorphism ......................................................................... .Greenatone schists ............................................... :.......................... Character ............................................................................... Included quartzite ...................................................................... Occurrence ............................................................................ Age ................................................................................... Structure .............................................................................. Metamorphiam ......................................................................... 4 CONTENTS. Copper Mountain area--Continued . Geology--Continued . Page. Igneous rocks .................................................................................... 33 General features............................................................................. 33 Granitic intrusives .......................................................................... 33 Types ................................................................................... 33 Diorite ................................................................................. 33 Granodiorite............................................................................ 35 Syenite. ................................................................................ 36 Gabbro ............................................... :................................ 36 Distribution of the igneous rocks ............................................................. 37 Structural features................................... :....................................... 37 Marginal phenomena ........................................................................ 39 Age ................. ... .................................................................. Dike rocks ................................................................................. Pegmatitea and aplitea ................................................................... Pyroxene-feldspar dikes ................................................................. Porphyries............................................. ................................. Lamprophyre ........................................................................... Diabase ................................................................................. Geologic history .................................................................................... Copper ores of the Copper Mountain area ............................................................ General character ............................................................................... Geographic and geologic distribution ............................................................. Types of ore deposits............................................................................ Contact deposits ............................................................................... 45 The contact zone .................., ........................................................ 45 The ore in the contact zone .................................................................. 45 Typea of contact deposits ............................................................... 45 Chalcopyrite-magnetite type ............................................................. Chalcopyrite-pyrrhotite type ............................................................. Relation of intruded rocks to contact deposits ........................ :................... Location of minable ore .................................................................. veindeposi ts .................................................................................. Diseeminated deposits........................................................................... Minerals of the deposits......................................................................... Scope of the discussion ...................................................................... Primary ore minerals ....................................................................... Secondary ore minerals ...................................................................... Gangueminerals ........................................................................... Mining in the Copper Mountain area .................................................................. General conditions .............................................................................. Early discoveries ............................................................................... The mines ..................................................................................... Alaska Copper Co ........................................................................... AlmhIndust&lCo ........................................................................ Jumbogroup ...........................................................................