LA-ICP-MS zircon U-Pb geochronology in the Altar porphyry copper Project, Andes Main Cordillera of San Juan, Argentina

Abstract

The “now amagmatic” Andean flat-slab segment (28-33ºS) (Cahill e Isacks, 1992) is known for its Cu-Mo-Au mineralization ‘fertility’ and hosts high-sulphidation epithermal deposits such as La Coipa (6 million ounces of Au equivalent,~24 to 17 Ma), Pascua (12 Moz Au, ~9 to 6 Ma) and El Indio (12 Moz Au,~9 to 6 Ma) and world-class porphyry Cu-Mo deposits such as Pachón-Los Pelambres (21 Mt Cu,~11 to 10 Ma), Los Bronces-Rio Blanco (49 Mt Cu,~6 to 4 Ma) and El Teniente (75 Mt Cu,~6 to 4 Ma). The Altar Porphyry Cu-(Au-Mo) project (31º 29' S, 70º 28´ W) occurs in the southern portion of the Andean flat-slab segment, within a “cluster” of Cu (Au) prospects including Piuquenes, La Coipa, Calderón, Rincones de Araya and Los Azules and next to the worldclass porphyry Cu deposits of Los Pelambres, in Chile, and Pachón, in Argentina. Despite the high economic value, the geology of this area is poorly known. This contribution presents new geological, geocronologic and isotopic data for Altar rocks that provide insights into the magmatic evolution of this region during Miocene times.