The subduction of the Copiapó aseismic ridge, is the causing of the formation of metallic minerals deposits in north of Chile and Argentina?

Abstract

The results obtained in this work evince that the metallic mineral deposits located in the northern region of the Chilean-Pampean flat slab (in northern Chile and north-western Argentina), at approximately 27° 30′S, would be related to the subduction of the Copiapó aseismic ridge. The analysis of the gravity anomalies and vertical gravity gradient allows inferring a deflection and truncation of the main trend of the Andean structures at the extrapolated zone of the Copiapó ridge beneath South America. Thus, the general NNE-trend of the Andean structures are rotated locally to an ENE-strike within the area of the Ojos del Salado – San Buena Ventura lineament. We explain that this anomalous behavior of the gravity derived anomalies is related to the deformational effects imprinted by the ridge subduction. Regions with a low subduction angle (<30° to horizontal) are related to large mineralization due to fluids released by dehydration of the subducting crust. In addition, a higher degree of mantle melting could be produced by a thicker oceanic crust. Therefore, we interpret that the processes associated to the subduction of the Copiapó aseismic ridge (emplaced on a thickened oceanic crust due to a local compensation of the seamounts) are the cause of formation and emplacement of big metallic mineral deposits in this region of Chile and Argentina. Keywords: Aseismic ridge, Satellite gravity, Ojos del Salado-San Buena Ventura lineament, Metallic mineral deposits