CONICET | Buscador de Institutos y Recursos Humanos

We developed a 3D density model of the continental crust, the subducted plate and the upper mantle of the Central Andes between 20°-29°S and 74°-61°W through the forward modelling of Bouguer anomaly. The goal of this contribution is to gain insight on the lithospheric structure integrating the available information (geophysical, geologic, petrologic, and geochemical) in a single model. The geometry of our model is defined and constrained by hypocenter location, reflection and refraction on and off-shore seismic lines, travel time and attenuation tomography, receiver function analysis, magnetotelluric studies, thermal models and balanced structural cross sections. The densities allocated to the different bodies were calculated considering petrologic and geochemical data and pressure and temperature conditions. The model consists of 31 parallel E-W vertical planes, where the continental crust comprises distinct bodies, which represent the different morphotectonic units of the Central Andes. We included a partial melting zone at midcrustal depths under the Altiplano-Puna (Low Velocity Zone) and considered the presence of a rheologically strong block beneath the Salar de Atacama basin, according to recent seismic studies. Contour maps of the depth of the continental Moho, the thickness of the lower crust and the depth to the top of the asthenosphere below South America were produced. The possible percentage of partial melt in the Central Andes Low Velocity Zone was estimated. The residual anomaly was calculated by subtracting from the Bouguer anomaly the gravimetric effect of the modelled subducted slab and of the modelled Moho. In this study we demonstrate how 3D gravity modelling, integrating geophysical, geologic and petrologic information, can help to reveal the lithospheric structure of the Central Andes.

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