Age of magmatic events in the Eopaleozoic Jaibaras Basin, NE Brazil: Constraints from U-Pb zircon geochronology

Abstract

The Late Neoproterozoic to Early Paleozoic Jaibaras Basin is located between the southeastern margin of the Medio Coreaú Domain (MCD) and northwestern edge of the Cear a Central Domain (CCD) of the Borborema Province, Northeastern Brazil, which is also the location of the main axis of the Transbrasiliano Lineament. The lower volcano-sedimentary rocks in the Jaibaras Basin are composed of two lower Vendian-Cambrian sedimentary units, Massape paraconglomerates and Pacuj ^ a reddish sandstones, and one volcanic unit, the Parapuí Formation. The whole set is partially crosscut by two post-tectonic granite suites, the Mucambo and Meruoca plutonic bodies. The upper Cambrian-Ordovician sequence in the basin is represented by the polymitic conglomerates of the Aprazível Formation. In order to gain information on the relationship between magmatic and sedimentary events, in this paper we present new U-Pb zircon and K-Ar geochronological analyses that have been carried out on both volcanic and plutonic magmatic lithotypes. According to our data, emplacement of the Meruoca Pluton took place over a large time interval (539 Ma to 523 Ma), and was synchronous with the emplacement of the Mucambo Pluton (532 Ma) and at lower part of the Parapuí Suite (535 Ma). The last ductile event related to the movement of the Sobral-Pedro II Shear Zone is dated at 530 Ma, and the subsequent emplacement of the Aroeira Suíte dikes occurred between 524 and 500 Ma (Middle Cambrian). Finally, at 492-484 Mais the age of cooling of the magmatic system related to the Aroeiras Suite.