Lithospheric and sublithospheric deformation under the Borborema Province of northeastern Brazil from receiver function harmonic stripping
|Author(s)||Lamarque Gaelle1, 2, Julià Jordi1, 3|
|Affiliation(s)||1 : Programa do Pós-Graduação em Geodinâmica e Geofísica, Universidade Federal do Rio Grande do Norte, Natal, RN CEP 59078-090, Brazil
2 : Ifremer, Geosciences Marines, Centre de Brest, 29280 Plouzané, France
3 : Departamento de Geofísica, Universidade Federal do Rio Grande do Norte, Natal, RN CEP 59078-970, Brazil
|Source||Solid Earth (1869-9510) (Copernicus GmbH), 2019-06 , Vol. 10 , N. 3 , P. 893-905|
|Note||Special issue Advances in seismic imaging across the scales Editor(s): M. Malinowski, C. M. Krawczyk, R. Carbonell, and N. Rawlinson|
The depth-dependent anisotropic structure of the lithosphere under the Borborema Province in northeast Brazil has been investigated via harmonic stripping of receiver functions developed at 39 stations in the region. This method retrieves the first (k=1) and second (k=2) degree harmonics of a receiver function dataset, which characterize seismic anisotropy beneath a seismic station. Anisotropic fabrics are in turn directly related to the deformation of the lithosphere from past and current tectonic processes. Our results reveal the presence of anisotropy within the crust and the lithospheric mantle throughout the entire province. Most stations in the continental interior report consistent anisotropic orientations in the crust and lithospheric mantle, suggesting a dominant northeast–southwest pervasive deformation along lithospheric-scale shear zones developed during the Brasiliano–Pan-African orogeny. Several stations aligned along a northeast–southwest trend located above the (now aborted) Mesozoic Cariri–Potiguar rift display large uncertainties for the fast-axis direction. This non-azimuthal anisotropy may be related to a complex anisotropic fabric resulting from a combination of deformation along the ancient collision between Precambrian blocks, Mesozoic extension and thermomechanical erosion dragging by sublithospheric flow. Finally, several stations along the Atlantic coast reveal depth-dependent anisotropic orientations roughly (sub)perpendicular to the margin. These results suggest a more recent overprint, probably related to the presence of frozen anisotropy in the lithosphere due to stretching and rifting during the opening of the South Atlantic.