The Geology of the Upper Mississippi Valley Zinc-Lead District

Abstract

Second and third stages 125 Gash-vein, joint-controlled ore bodies 128 Placer and residual deposits 130 Occurrence and textures of the ores in the rocks of Middle Ordovician age 131 Vein fillings and replacement veins along fractures and bedding planes 131 Cavity fillings in fault breccias and fractured zones 133 Cavity fillings in solution breccias 133 Disseminations by replacement and impregnation deposits in favorable beds___ 134 Ore-body relations in the Cambrian, Lower and Upper Ordovician and Silurian rocks 135 Mineral deposits in the Cambrian rocks 135 Mineral deposits in the Prairie du Chien group_ 136 Mineral deposits in the St. Peter sandstone 137 Mineral deposits in the Maquoketa formation_ _ 137 Mineral deposits in dolomite of Silurian age_ _ 138 Page Mines in the upper Mississippi Valley-Continued Mines in the main part of the mineralized district-Continued Mines in Illinois-Continued Galena subdistrict 176 Pittsburg or Great Western mine