Geothermobarometry of igneous rocks from Afonso Cláudio intrusive complex (Espírito Santo state, Southeastern Brazil), Araçuaí-West Congo Orogen: Further evidence for deep emplacement levels

Abstract The Afonso Claudio Intrusive Complex (ACIC) is an inversely zoned pluton that intruded the Aracuai-West Congo Orogen (AWCO) during the orogenic collapse, which lasted from 530 to 480 Ma. It is hosted in orthogneisses of the Pre-collisional Supersuite and paragneisses from Nova Venecia Complex and is mostly constituted by two off-centered mafic cores, composed by monzogabbro and monzodiorite, surrounded by quartz monzonite hills. Mingling and mixing zones were mapped between these rocks, where jotunite and quartz mangerite were locally found. In this study, we present a petrographic, mineral chemistry and geothermobarometric study concerning the most abundant ACIC rocks. These rocks showed emplacement conditions corresponding to middle and lower crust, which are similar to crustal levels estimated for its main host rocks. In addition, the ACIC rocks enclose many host rocks xenoliths, with some of them showing melting evidences. These evidences suggest that the ACIC host rocks were one of the main sources of the ACIC felsic magmas, which contaminated mantle mafic magmas during ACIC evolution. Due to the similarities between the AWCO post-collisional rocks, present work concludes that post-collisional plutons intruded between the middle and lower crust levels and were contaminated by its host rocks during its evolution and cooling, contributing also to the felsic magma sources.