Mantle anisotropy and asthenospheric flow around cratons in southeastern South America

Autor(es)

de Melo, Bruna Chagas ^[1] ; Assumpcao, Marcelo ^[1] ; Team, 3-Basins Project

Afiliação do(s) autor(es)

^[1] Inst Geofis Astron & Ciencias Atmosfer, Dept Geofis, Ctr Sismol, BR-05508090 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Geophysical Journal International; v. 215, n. 1, p. 494-506, OCT 2018.
• Citações Web of Science: 2

Resumo

Upper mantle seismic anisotropy is one of the most important means to study dynamics of the Earth's interior. It has been extensively used to infer past and present mantle dynamics and continental evolution. Seismic anisotropy in the upper mantle can be measured by the method of shear wave splitting (SWS) of core refracted phases, such as SKS. Previous studies of SWS in South America concentrated mainly along the Andes and in southeast Brazil. Now we add extra measurements in the area of the Pantanal and Chaco-Parana basins, as part of the FAPESP `3-Basins' thematic project. With the splitting results of 47 new stations, we have a more complete and robust anisotropy map of the South America stable platform. On average, over most of the midplate continent, the fast polarizations have an average E-W orientation, which is close to the absolute plate motion given by the hotspot reference model HS3-NUVEL-1A (median deviation of 15.7 degrees). However, recent models of subduction induced mantle flow beneath South America provide a better explanation for the fast orientations (median deviation of approximate to 12 degrees). Nevertheless, detailed analyses of the fast orientations indicate an additional component of mantle flow deviating from the cratonic blocks, at the Sao Francisco and Amazon cratons and beneath the Parana basin (called Paranapanema block). Large delay times may indicate a strong asthenospheric channel, a more coherent flow or a thicker asthenosphere, between the Paranapanema block and the Amazon craton. Similarly, small delay times may indicate thinner anisotropic asthenosphere beneath the Paranapanema block. (AU)

• Processo FAPESP: 13/24215-6 - As bacias do Pantanal, Chaco e Paraná (PCPB): evolução e estrutura sísmica da crosta e manto superior
• Beneficiário: Marcelo Sousa de Assumpção
• Modalidade de apoio: Auxílio à Pesquisa - Temático