Insights on the lithospheric density structure of the Southern Central Andes and their foreland

CONSTANZA RODRIGUEZ PICEDA; MAGDALENA SCHECK-WENDEROTH; MARÍA LAURA GÓMEZ DACAL; BOTT, JUDITH; CLAUDIA PREZZI; MANFRED STRECKER

Congreso; Latin American Colloquium of Geosciences; 2019

In a subduction setting, the overriding plate structure is one of the major controls in the formation of strong and weak areas within the crust, affecting the localization and extent of deformation. In the case of the Andes, the orogeny is originated by the subduction of the Nazca oceanic plate beneath the South American continental plate. Previous studies aimed to constrain lithospheric-scale density and structural heterogeneities in the Southern Central Andes, in the Puna and the Chaco-Paraná basin (~20 - 27°S). This study focuses on the southernmost segment of Central Andes (~27° - 40°S), characterized by a strong N-S and E-W variation in the crustal deformation style and intensity.We present a characterization of the present-day state of the lithosphere, regarding the density variation and configuration of the sediments, crust and mantle by building a lithospheric-scale model consistent with both the available geological and seismic data and with the observed gravity field. A gravity forward modelling was carried out using IGMAS+ (©Transinsight GmbH). The model consist of a continental plate with a two-layer crust being subducted by an oceanic plate (Fig.1). The configuration of sediments, crystalline crust and lithospheric mantle was constrained by the geological and seismic data, while the intracrustal discontinuity was modified in order to reproduce the observed gravity field. Besides being able to assess the geometry and composition within the lithosphere, the resulting model allowed us to evaluate the isostatic state of the crust.This is a first step on the way to estimate the thermal and rheological state of the lithosphere in the overriding plate to further investigate the link between its compositional, thermal and rheological heterogeneities with the geometry of the subducting plate and the deformation style. This project is supported by the International Research Training Group StRATEGy.