The Paleoproterozoic Eastern Bahia Orogenic Domain

Abstract

The Paleoproterozoic Eastern Bahia orogenic domain occupies an approximately 200 km-wide area in the northern Sao Francisco craton, located between the Atlantic coast and the interior plateau of Bahia state known as the Chapada Diamantina. Together with its African counterpart, the West Central African belt of Gabon, the Eastern Bahia orogenic domain form a complete segment of a collisional orogen developed during the transition between the Rhyacian and Orosirian periods. Exposed in the level of its roots, the Eastern Bahia orogenic domain involves mainly amphibolite to granulite facies rocks that characterize three distinct Archean basement blocks (the Gaviao, Jequie and Serrinha blocks) and a Neoarchean magmatic arc (the Itabuna-Salvador-Curaca belt, ISAC belt). The Paleoproterozoic rock record of the domain includes volcanic, sedimentary and granitic assemblages deposited and emplaced during its pre-, syn- and post-collisional evolutionary stages. The supracrustal rocks are represented by continental to marine metasedimentary successions of presumed Siderian to Rhyacian ages, as well as volcano-sedimentary accumulated in intra- and back-arc basins settings. The granitic rocks comprise five distinct groups of relatively small plutons emplaced between 2320 and 1960 Ma, mainly in the Gaviao and Serrinha blocks. The structural framework of the domain involves sinuous NS-trending and E-dipping reverse, reverse-sinistral to sinistral strike-slip faults and ductile shear zones. These structures nucleated during a second and syn-metamorphic deformation phase dated at ca. 2080 Ma, which was preceded by the convergence and collision of the various basement blocks of the domain at around 2100 Ma. This chapter contains a synthesis on the stratigraphy, overall structure and Paleoproterozoic evolutionary history of the domain.