Kinematics, displacement and timing of shear zone junctions: The case of the Taperoá-Patos shear system, Borborema Province, NE Brazil

Abstract

Networks of interacting transcurrent shear zones are a hallmark feature of mid- to late-stage orogenic deformation and often drive significant displacement. In one of the largest of such systems on Earth, the Neoproterozoic Borborema Province of NE Brazil, shear zones with opposing shear senses are common but still poorly constrained in terms of relative chronology and total offset. High-resolution multispectral Sentinel 2 imagery from the vicinity of the junction of the left-lateral Taperoá and right-lateral Patos shear zones was processed to generate accurate and large-scale structural maps. Selective Principal Component Analysis was evaluated using simulated principal component scores of selected reference mineral spectra. False color Crosta composites yielded reliable lithological contrasts for extraction of lineaments and mapping of lithological units which are displaced by the Taperoá shear zone by 52 km. UPb ages obtained from the Lagoa do Meio (608 ± 5 Ma) and Itapetim (617 ± 5 Ma) plutons and their mapped continuous spatial connection along the shear zone core show their protracted crystallization history (potentially spanning more than 10 Myr) in a pre-transcurrent setting, due to their displacement of 52 km. Together with structural profiles of other key units, such as the 590 Ma alkaline granites and the c. 980 Ma host-regional metabasic units, these observations constitute kinematic evidence that the Taperoá shear zone was initiated after 590 Ma and grew in an intra-terrane setting. With this timing, it was potentially synchronous with early shearing of the Patos shear zone, thus constituting with it a dextral closing zipper.