Petrography and geochemistry of the orthoanfibolites of the units Novo Gosto Gentileza, Canindé Domain, Sergipana Fold Band, Northeast Brazil

Abstract

The difficult to define the geotectonic environment, as well as the petrogenesis of these rocks is influenced by the intense deformation and metamorphism processes, which oblitered part of the main original features of these rocks. This work aims to understand the igneous processes involved in the genesis of ortho-amphibolites protoliths from both units, based on field, petrographic and geochemical data. The petrographic data suggest that the ortho-amphibolites of these units were metamorphosed in the Amphibolite Facies and they were submitted to retrometamorphic condition processes in the Greenschist Facies. Based on microscopic observations, the othoamphibolites show igneous relics features. The geochemical data indicate that the protolith of from Novo Gosto Unit corresponds to tholeiitic basalts, while those from the Gentileza Unit correspond mainly to andesites and basaltic andesites, with tholeiitic to calc-alkaline af