Lithospheric 3D gravity modelling using upper-mantle density constraints: Towards a characterization of the crustal configuration in the North Patagonian Massif area, Argentina

The North Patagonian Massif is an Argentinean plateau that has an average height of 1200 m and stands from 500 to 700 m above the neighboring areas. During Paleogene, it suffered a sudden uplift of more than 1200 m without noticeable internal deformation; thus, it could be related to isostatic disequilibrium. To shed light on the geodynamic development of the area it is necessary to characterize the present-day configuration of the crust. In this study, a lithospheric-scale 3D density model was developed by integrating all the available data of the area with the objective of assessing the depth of the crust-mantle discontinuity (Moho). During the construction of the initial density model, we tested different mantle density scenarios obtained using P- and S-wave velocities from tomographic models, converting them into densities and comparing the conversions with densities obtained from xenoliths. Below the North Patagonian Massif plateau, we have derived a Moho depth between 40 and 50 km which is from 2 to 7 km deeper than its surroundings. There is an evident correlation between high topography and deep Moho that would indicate isostatic equilibrium at present. The model results provide a new approach to the Moho depth in an area where there is no seismic constraining information about this discontinuity. In addition, we found a spatial correlation between the variation of the mean crustal density and the location of the Paleozoic terranes that were proposed to constitute the basement of Argentina.