Lead isotope provinces of the Central Andes inferred from ores and crustal rocks

Abstract

The central Andean Cordillera of Peru, Bolivia, northwestern Argentina, and northern Chile may be divided into three fundamental geologic provinces, based on the age and dominant geology of the exposed rocks. We define these provinces as follows:Province I: The coastal volcanic arc, comprising the Jurassic-early Tertiary coastal batholith complex and related volcanic rocks of the Western Cordillera and coastal belt. Based on differences in the isotopic composition of ore lead, province I is further subdivided into subprovince Ia, comprising the coastal volcanic belt of northern and central Chile; subprovince Ib, in central Peru north of 13 degrees S; and subprovince Ic, in southern Peru and northernmost Chile between 19 degrees S and 13 degrees S.Province II: The Jurassic and Cretaceous miogeosynclinal sedimentary belt that dominates the geology of the high Andes of Peru.Province III: The Eastern Cordillera of southeastern Peru, central Bolivia and northwestern Argentina, made up mainly of early Paleozoic clastic sediments. We have also divided this into two subprovinces due to different ore lead isotope characteristics: subprovince IIIa in Bolivia and northern Argentina, and subprovince IIIb in southeastern Peru.These provinces are bordered by noncordilleran units of the Brazil and Guyana Shields, the Arequipa massif, and the metamorphic terranes of southern Chile and central-western Argentina.We present 45 new analyses of ore minerals from 31 mining districts and two of hos…