The granulitic roots of the Salvador-Esplanada-Boquim Belt, São Francisco Craton, Bahia-Sergipe, Brazil
DOI:
https://doi.org/10.11606/issn.2316-9095.v18-134238Keywords:
Granulite, Geochemistry, Geochronology, Salvador-Esplanada-Boquim Belt.Abstract
The Salvador-Esplanada-Boquim Belt is probably a northeastern branch of the Itabuna-Salvador-Curaçá Orogen. This study, which is unprecedented in the region, presents the petrographic, petrochemical and geochronological characterization of granulite rocks from the central-northern portion of this belt, where four acidic and intermediate granulite units were separated, in addition to mafic granulite bands, aluminous granulites and quartzites. These four acidic and intermediate units are foliate orthogranulites, where mafic granulites are embedded in the form of lenses. These rocks were crossed by orosirian, dacitics-rhyolite dykes, (Arauá Dykes). The lithogeochemical study of acidics and intermediate granulites has revealed four calcium-alkaline series from low to high K, named: (i) enderbitic (Ed1), (ii) enderbitic (Ed2); (iii) charnockitic of monzogranitic composition (MCh) and (iv) charnoenderbitic (Ch-Ed). Multielement diagrams indicate that the four units have negative Nb, Ti and P anomalies and low levels of HFSE, suggesting that there is a genetic association attached to subduction zones and volcanic arcs. On the other hand, the mafic granulites indicated a tholeiitic affiliation with charac-teristics of the MORB type. The geochronological data indicate ages that suggest the presence of tectonic events in this area, namely: (i) the formation of the granulite’s protholith (Ed2) at 2.90 Ga (model-age TDM-Nd); (ii) the crystallization of the granulite (Ed2) at 2582 ± 11 Ma and MCh at 2473 ± 13 Ma; (iii) regional metamorphism aged 2087 Ma and 2073 Ma, and (iv) the filling in of faults in the form of dykes around 2015 ± 12 Ma. The data obtained, especially with regard to lithogeochemistry, allow for the interpretation that these high-grade metamorphic rocks are suited to those of the volcanic arc type. Upon coliding on the Paleoproterozoic with the Serrinha Block, located to the west of the study area, these high-grade metamorphic rocks formed a mountain chain which eroded, exposing their granulite roots.
Downloads
Downloads
Published
Issue
Section
License
Authors who publish in this journal shall comply with the following terms:
- Authors keep their copyright and grant to Geologia USP: Série Científica the right of first publication, with the paper under the Creative Commons BY-NC-SA license (summary of the license: https://creativecommons.org/licenses/by-nc-sa/4.0 | full text of the license: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode) that allows the non-commercial sharing of the paper and granting the proper copyrights of the first publication in this journal.
- Authors are authorized to take additional contracts separately, for non-exclusive distribution of the version of the paper published in this journal (publish in institutional repository or as a book chapter), granting the proper copyrights of first publication in this journal.
- Authors are allowed and encouraged to publish and distribute their paper online (in institutional repositories or their personal page) at any point before or during the editorial process, since this can generate productive changes as well as increase the impact and citation of the published paper (See The effect of Open Access and downloads on citation impact).