Rio Maria granodiorite and associated rocks of Ourilândia do Norte – Carajás province: Petrography, geochemistry and implications for sanukitoid petrogenesis

Abstract

Ourilândia do Norte rocks are located near Rio Maria-Carajás domains boundary and are associated to Rio Maria Mesoarchean sanukitoid. Two groups were defined on the basis of geochemistry: (i) quartz-monzodiorites and granitoids (tonalite and granodiorite) which match to the sanukitoid (stricto sensu); and (ii) enclaves and (quartz) diorites that do not. Despite this, these rocks are spatially and temporally associated and they develop microstructures under three dynamic recrystallization regimes: (i) bulging recrystallization (300–700 °C); (ii) subgrain rotation recrystallization (<700 °C); (iii) grain boundary migration recrystallization (>600 °C). Furthermore, they belong to medium to high potassium calc-alkaline series, being magnesian and mainly metaluminous. The Mg#, Cr and Ni abundances point out an ultramafic mantle source. Variation of LILE, Nb/Y, (La/Yb)N and Sr/Y contents indicate a metasomatized mantle by two independent agents, namely TTG-like melt and aqueous fluids, at different depths. In this way, quartz-monzodiorites and granitoids were derived from fractionation of a mafic magma, whose source is a TTG-metasomatized mantle, at greater depths, while enclaves and (quartz) diorites were generated from a fluid-metasomatized mantle, at shallower depths. The close spatial and temporal association of rocks with sanukitoid (quartz-monzodiorites and granitoids) and BADR (enclaves and (quartz) diorites) signature suggest that Ourilândia do Norte granitoids were generated in close spatial and temporal association with active subduction.