PB ISOTOPES DEFINE BASEMENT DOMAINS OF THE ALTIPLANO, CENTRAL ANDES

Detailed Pb isotopic maps of the central Andes, based on 345 (163 prev iously published, 182 new) analyses of ores, volcanic rocks, and their host rocks, elucidate the gross structure of the basement and reveal that several isotopically distinct basement domains are juxtaposed in this region. The data clearly show that most of the Pb in central Ande an igneous and ore samples is derived from the local basement, includi ng Pb in ore deposits of the Bolivian tin belt. Some of the isotopic d omain boundaries correspond to geologic structures and the residual gr avity pattern, as well as to metallogenic boundaries such as the weste rn edge of the Bolivian tin belt.