Abstract. 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.
Fragments of juvenile Siderian continental crust in the Rio Piranhas-Seridó Domain, Borborema Province, Northeastern Brazil, as deduced by zircon U-Pb and whole-rock Sm-Nd systematics
