Timing of the HT/LP transpression in the Neoproterozoic Serido Belt (Borborema Province, Brazil): Constraints from U-Pb (SHRIMP) geochronology and implications for the connections between NE Brazil and West Africa

The Serido schist belt is a classical domain of the Borborema Province (NE Brazil) recording crustal melting at HT/LP conditions in a tectonic setting dominated by dextral transpressive deformation. A comparable tectonometamorphic setting has been described in the Pan-African Igarra and Ilesha schist belts of south Nigeria (Africa). The HT-transpression of the Serido has previously been imprecisely dated by using a range of isotopic methods on a suite of syntectonic granites. We provide new U-Pb zircon ages of the Acari granite and Santa Luzia migmatite that constrain the HT/LP metamorphism of the Serido at c. 575 Ma. Anisotropy of magnetic susceptibility of the Santa Luzia migmatite shows that the magnetic fabric records the NE-trending dextral kinematics similar to those previously described in the Acari pluton. On the other hand, the U-Pb ages of the Totoro pluton provide evidence for an older, mostly mafic to intermediate magmatism intruding the pelitic schist that precedes the HT/LP metamorphism by approximately 15 m.y. In contrast with the Acari pluton and Santa Luzia migmatite, the magnetic fabrics of Totoro show a concentric steep-dipping structure apparently related to magma ascent. Thermobarometric studies in the Serido, Igarra and Ilesha schist belts indicate that a large domain in the northern Borborema and south of the Nigeria shields was deformed at a high temperature and at relatively shallow depths. Although the tectonic setting for such a post-collision HT event remains an open issue, it allows us nevertheless to refine the across-Atlantic geological correlation between the continents. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.