Lithospheric temperature and rheology of the North Patagonian Massif plateau, Argentina

MARÍA LAURA GÓMEZ DACAL; MAGDALENA SCHECK-WENDEROTH; CACACE, MAURO; ARAGÓN, EUGENIO; CLAUDIA TOCHO

Congreso; Latin American Colloquium of Geosciences; 2019

The North Patagonian Massif (NPM), in central Argentina, includes a plateau of an average altitude of 1200 m.a.s.l. mostly surrounded by basins that stand between 500 to 700 m below it. Geological observations and previous works indicate that the present-day elevation of the plateau was reached in the Paleogene by a sudden uplift that did not involve noticeable deformation. To gain insight into the causes of the uplift and the geodynamic development of the area, it is necessary to characterize the lithosphere in terms of its present-day physical properties.In this study, we present models of the three-dimensional lithospheric distribution of temperature in the area, as well as, of the maximum differential stress that the rocks are able to resist without experiencing either brittle or ductile deformation under given pressure and temperature conditions. For the thermal calculation, we used the software GOLEM and, in the case of the strength calculations, a code that resolves Byerlee?s law for the brittle part and power-law rheology functions for the ductile one. We use as a base for the models, an existing gravity constrained 3D geological model that was developed in a previous project. It includes all available geological and geophysical information to constrain the geometries and the lithologies of the model units and was compared to the observed gravity to obtain the depth of the Moho. By using the model configuration, we assigned to each unit corresponding thermal properties to calculate the thermal field and afterwards also parameterized the model in terms of mechanical properties to obtain the strength distribution within the lithosphere.With this contribution, we present a comparison between the model derived physical properties inside the plateau with those obtained for the surrounding areas. The predicted present-day temperature and strength differ significantly from one region to the other, differentiating the NPM plateau in terms of these characteristics. This analysis helps to test hypotheses on the influence of the temperature and strength distribution in the geodynamics of the region and brings up for discussion the causes of the formation of the plateau and its present-day elevation.