Mineral Deposits in the West Chinati Stock, Chinati Mountains, Presidio County, Texas

The West Chinati stock, well exposed in San Antonio Canyon and immediately westward on slopes of the southwestern part of the Chinati Mountains, Presidio County, Texas, is a large stocklike body of porphyritic hornblende granite cut by numerous dikes and irregular-shaped plutons of rhyolite, rhyolite porphyry, microgranite, trachyte porphyry, diorite, and igneous breccia. Fissure veins developed in wide and long sheeted zones which strike E-W and N. 50" E. containpotentially commercial deposits of lead-zinc-silver fluorspar, minerals including galena (PbS), sphalerite (ZnS), argentite (Ag2S), cerargyrite (AgCl), and fluorite (CaF2). Minor amounts of chalcopyrite (CuFeS2) and oxidized copper minerals also occur in the fissure vein deposits. Marginal bodies of rhyolite, rhyolite porphyry, and trachyte porphyry contain disseminated copper mineralization and possibly host commercial porphyry-type copper deposits.