Geology and Mineral Deposits of the Minnie Moore and Bullion Mineralized Areas Blaine County Idaho

<p>In the early 1880?s the discovery of rich ores in the Minnie Moore and Bullion mineralized areas sparked a rush to settle and develop the Wood River valley. Silver and lead discoveries in these areas spurred the boom in mining after completion of the Oregon Short Line Railroad to Hailey in 1883. In both areas the ore comprises galena sphalerite and tetrahedrite in a gangue of siderite calcite or quartz. Minor goldbearing quartz veins are also present. The ore is in fissure and replacement veins along fracture systems that formed in Late Cretaceous time after intrusion of nearby granodiorite or quartz diorite stocks. The ore formed under mesothermal conditions and heat was supplied by the nearby plutons. In the Minnie Moore area the mineralized veins are cut by low-angle normal faults that are of probable Eocene age. In the Minnie Moore mineralized area the host rock is the middle part of the Devonian Milligen Formation (the informal Lucky Coin limestone and Triumph argillite) which is the same stratigraphic level as the host ore in the rich Triumph mine northeast of Hailey. In the Bullion mineralized area the ore is hosted by the lower member of the Middle Pennsylvanian to Lower Permian Dollarhide Formation. Rich ore was mined in several tunnels that reached the Mayflower vein a northwest-striking mineralized shear zone. The deposits are thought to be mainly mesothermal veins that formed in association with Cretaceous magmatism. The syngenetic stratiform model of ore formation has often been applied to these deposits however no evidence of syngenetic mineralization was found in this study. Faulting has displaced most of the major orebodies and thus has made mining these deposits a challenge.</p><p>This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact and remains as true to the original work as possible. Therefore you will see the original copyright references library stamps (as most of these works have been housed in our most important libraries around the world) and other notations in the work.</p><p>This work is in the public domain in the United States of America and possibly other nations. Within the United States you may freely copy and distribute this work as no entity (individual or corporate) has a copyright on the body of the work.</p><p>As a reproduction of a historical artifact this work may contain missing or blurred pages poor pictures errant marks etc. Scholars believe and we concur that this work is important enough to be preserved reproduced and made generally available to the public. We appreciate your support of the preservation process and thank you for being an important part of keeping this knowledge alive and relevant.</p>