Petrografia e Geoquímica da Suíte Intrusiva Canindé, Faixa de Dobramentos Sergipana, NE-Brasil

Abstract

The Canindé Intrusive Suite (SIC) is located near the Canindé do São Francisco (SE) city. The SIC is constituted by elongated gabbroic body, at the NW-SE direction, which is intruded in the Novo Gosto-Mulungu metavolcanossedimentary rocks. In this work, the studies focused on the East and West portions of the SIC, and had as main objective to understand the field relationships and the magmatic processes involved in the generation of SIC rocks, through the petrographic and geochemical study of the rocks. In the Eastern portion, gabbros contain quartz-feldspathic magmatic injections that do not exhibit features of a physical mixture with the gabbroic rock, which characterize a mingling process. Locally, it has observed the contact between the gabbro and the biotite granite of the Sítios Novos Intrusive Suite. This contact shows features indicative of plasticity between the both magmas, suggesting contemporary magma placement. Microscopically, the gabbros of Eastern portion show, in an incipient way, chloritization reactions of augite and hornblende, epidotization of titanite and sericitization of plagioclase. These reactions have attributed to the volatile components migration of the magmatic injections. In the Western portion of the gabbroic body, hydrothermal fluids percolated fractures associated with the D3 deformation phase and modified the primary mineralogy of the metagabbro and metadiabase. In the metagabbro, there are chloritization reactions of augite and hornblende, epidotization of titanite and plagioclase. The plagioclase also shows sericitization, saussuritization and carbonation processes. The hydrothermal fluids also modified locally, the primary mineralogy of metadiabase, which shows fluid injection venules. The SIC rocks are chemically classified as gabbro and the geochemical analysis of the major elements, trace and REE evinced a calcium-alkaline geochemical affinity. The binary diagrams analysis, using the Zr as index of differentiation, allowed identification the presence of the magmatic processes such as apatite fractionation and plagioclase accumulation in rocks of the Western portion, as well as the fractionation of oxides in the majority of rocks, except in the metadiabase, which show oxides gravitational accumulation. The incompatibles and REE multielementary diagrams indicate the presence of two distinct sources, a more enriched one (rocks from the Eastern portion) and another more impoverished (rocks of the Western portion). The analysis of sample behaviour, in the geotectonic environment discriminant diagrams associated to the Nb, Ta and Ti negative anomalies presence, suggest that the SIC rocks were generated in a continental arc environment.