Abstract
Lateral escape tectonics mediated by strike-slip fault zones are an efficient mechanism of rock deformation in the continental crust of collision zones. The Borborema shear zone system, which shows dimensions comparable to the Cenozoic extrusion of Indochina, defines a lateral escape setting of the Brasilano orogeny in Northeastern Brazil. In this paper, the timing of high-grade metamorphism and compositions of the terranes involved in the shear deformation were investigated. The Patos shear corridor deforms the Siderian to Neoarchean rocks of the Granjeiro Complex that, in turn, form the basement of Seridó-Lavras da Mangabeira metapelites. U-Pb zircon ages and Sm-Nd whole-rock isotopic compositions indicate that the 2.80 – 2.35 Ga basement sequences mainly include juvenile material, whereas zircons from synkinematic migmatites indicate that the partial melting occurred in the Late Ediacaran (ca. 565 Ma). Cooling rates provided by 40Ar/39Ar range from 12 to 17°C/Ma, indicating a differential shear zone exhumation, in agreement with a transpressive setting. The presence of allochthonous Siderian sequences dismembered along the shear zone suggests that the Seridó-Granjeiro corridor defines a major tectonic boundary connected to the collisional front defined by the convergence of São Francisco-Congo and Amazonian cratons.
Highlights
Continental strike-slip faults are important components to understand the evolution of orogenic belts as they are often formed at plate margins, along conservative and convergent settings (Woodcock and Schubert 1994)
The remarkable similarities recorded in the detrital zircon spectra of the Lavras da Mangabeira and Seridó metasedimentary rocks, including some slices of metapelite and quartzite exposed along the central segment of the Patos shear zone, constitute a firm evidence connecting the Lavras da Mangabeira units to the Seridó belt
The occurrences of Archean and Siderian rocks scattered along the Patos shear zone combined with prominent magnetic anomaly trends confirm the connection between the GranjeiroSeridó and Ipueirinha basement sequences
Summary
Continental strike-slip faults are important components to understand the evolution of orogenic belts as they are often formed at plate margins, along conservative and convergent settings (Woodcock and Schubert 1994). The convergence between India and Eurasia in the Cenozoic is a worldwide reference frame in that major thrust faults form in the leading edge of the subducting India slab, whereas strike-slip faults develop laterally to provide space for the India plate to move North into the paleomargin of the Eurasian plate (Tapponnier et al 1982, Klemperer 2006). This indentation tectonic model would result in the extrusion to the Southeast of Indochina (Sundaland block; Fig. 1A), with the strike-slip faults accommodating the lateral escape. Another frame of reference for continental extrusion tectonics is the seismically active North Anatolian strike-slip fault that accommodates the lateral escape of the Anatolian plate sandwiched between the Arabian and
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