Metalogénesis

MARTA FRANCHINI; ANA MARÍA CASÉ

Relatorio del XVIII Congreso Geológico Argentino. Geología y Recursos Naturales de la provincia del Neuquén

Talleres Trama

Lugar: Buenos Aires; Año: 2011; p. 699 - 707

Metallogenesis. The genesis of ore deposits around Neuquén are associated to a particular stage in the tectonic evolution of the Gondwana margin and the Andean Cordillera. The oldest porphyry Cu (Mo) in the region was formed in a Lower Carboniferous magmatic arc. In the Early Jurassic, the marine depocenters of the retroarc region accumulated sedimentary and volcanic rocks erupted in an extensional tectonic regime. These rocks host exhalative banded iron, manganese, and chert deposits formed by the submarine hydrothermal activity. In the Upper Cretaceous-Paleocene, the uplift of the Cordillera de los Andes, the emplacement of epizonal plutons in the succesive magmatic arcs was followed by the exsolution of hydrothermal fluids, originating from porphyry Cu (Mo) systems to polymetallic skarns, breccias, and veins. These deposits are subeconomic because the plutons are relatively small and primitive in composition. Contractional events resulting in lesser amounts of crustal thickening, such as that which produced the Late Cretaceous uplift of the Andes of Neuquén, are considered metallogenetically less fertile. The ages of the quartz-pyrite-gold veins from the Andacollo district are not known, and neither is their genetic connection with a magmatic activity. Based on the structures of these veins, they have been associated with the upper Cretaceous-Paleocene magmatism. The inversion of the structures of the Dorsal de Huincul and the uplift of the Dorso de Los Chihuidos produced the migration of hydrocarbons and formation waters in the Neuquén Basin since early Cretaceous to Miocene, that appear to be responsible for the formation of the sediment-hosted stratabound Cu (U, V, Ag) mineralization, the most important are hosted in sandstones of the Neuquén Group. A more orthogonal subduction regime during the upper Oligocene-early Miocene produced extension in the retroarc, the eruption of alkaline basalts and associate iron mineralization. Key words: geotectonic setting, hydrothermal, sedimentary, magmatic processes