Petrochronology and tectonic evolution of the Southern Borborema Orogen during the Neoproterozoic in NE Brazil

Abstract

Inverted Barrovian metamorphic sequences are reported to be one of the major consequences of syn-metamorphic ductile thrust systems in continental collision zones. Located in Northeastern Brazil, the South Borborema Orogen is a well-preserved example of an ancient continental collision zone formed after the closure of the restricted sergipano ocean and the consequent agglutination of the Congo-Sao Francisco paleocontinent and the Borborema-Benino-Nigerian block at c. 600 Ma ago. Ductile thrust systems outline an inverted Barrovian-type metamorphic sequence analogous to modern collisional orogens, varying from greenschist facies in the bottom to upper amphibolite/granulite transition at the top towards the metamorphic-anatectic core. This project aims to investigate the duration, conditions, and rates of tectonic processes related to metamorphic inversion during the South Borborema Orogeny in the Neoproterozoic. A campaign-style 4D pressure-temperature-time-deformation investigation is proposed here, using zircon, monazite, and titanite Th-U-Pb petrochronology (LA-ICP-MS), thermodynamic modeling and in situ trace element mapping (LA-ICP-TOFMS) on profiles transverse to the thermal structure of the orogen. This integrated approach has the potential to elucidate the mechanisms that drove the inversion of regional Barrovian metamorphism, as well as to assess possible heat sources, rates, and duration of orogeny from an archetype collisional orogen formed after the closure of the restricted sergipano ocean in the center of West Gondwana. (AU)