10.48380/DGGV-CR8S-BC72
Thermo-compositional models of the West Gondwana cratons
Finger, Nils-Peter
Nils-Peter
Finger
GFZ Potsdam, Germany
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
Free University Berlin, Germany
Freie Universität Berlin
Kaban, Mikhail K.
Mikhail K.
Kaban
GFZ Potsdam, Germany
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
Schmidt Institute of Physics of the Earth, RAS, Moscow, Russia
Schmidt Institute of Physics of the Earth
Tesauro, Magdala
Magdala
Tesauro
University of Trieste, Trieste, Italy.
University of Trieste
University of Utrecht, Utrecht, Netherlands
Utrecht University
Mooney, Walter D.
Walter D.
Mooney
US Geological Survey, Menlo Park, USA.
United States Geological Survey
Thomas, Maik
Maik
Thomas
GFZ Potsdam, Germany
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
Free University Berlin, Germany
Freie Universität Berlin
Abstract
2021
en
When Western Gondwana broke apart into the South American and African continents ca.120 Ma ago, some of its cratons were broken apart as well. Following the isopycnic hypothesis, their long-term stability and often neutral to positive buoyancy can be explained by the counteracting effects of cooling (density increase) and iron depletion (density decrease). To separate these effects, we created the presented models following an iterative integrated approach using mainly seismic and gravity data. In the first step, seismic models of Depth to the Moho were created to allow correction of the gravity field and calculation of the residual topography. Second, based on mineral physics and S-wave tomography, we assessed temperature variations in the uppermost mantle and subtracted their effects from both residual gravity and topography. Afterwards, a joint inversion enables determination of potential compositional variations. Adapting the initially juvenile mantle composition leads to a change of thermal effects, thus the process was repeated iteratively until convergence. In result, we obtained self-consistent models of temperature, thermal and compositional density variations, and Mg, a measure of iron depletion. Our results show deep depleted cratonic roots under the Amazonas, São Francisco, Paranapanema (South America), West African, Northern to Central Congo and Zimbabwe Cratons (Africa). Depletion appears to be mostly absent in the Rio de la Plata Craton of South America and its proposed African counterpart, the Southern Congo Craton as well as the Kaapvaal Craton below 100 km depth and the Tanzania and Uganda Cratons.
Germany, Russia, Italy, Netherlands, USA
Deutsche Geologische Gesellschaft - Geologische Vereinigung e.V. (DGGV)
2021