Lithological and structural controls on the emplacement of a Neoarchean plutonic complex in the Carajás province, southeastern Amazonian craton (Brazil)

Abstract

New geological and geochronological (Pb-Pb evaporation) data from the Vila Jussara suite, a representative of the Neoarchean granitoids of the Carajás province, southeastern Amazonian craton (Brazil), are discussed. The Vila Jussara suite crops out as a series of coalescing plutons elongated in the E-W direction. These plutons generally have sigmoidal shapes, and steep dips (75–85°) that follow the regional trend. The centermost areas of plutons are generally slightly deformed, while the marginal portions display mylonitic aspect and are delimited by sinistral shear zones belonging to the transcurrent system of the Itacaiúnas shear belt. These granitoids cover a large compositional spectrum, with four main lithotypes: (i) Seriated biotite-hornblende monzogranite; (ii) biotite-hornblende tonalite; (iii) porphyritic biotite monzogranite-granodiorite; and (iv) porphyritic hornblende-biotite monzogranite-granodiorite. The microstructural analysis of the studied rocks reveals: (i) microfractures in feldspar phenocrysts, filled with a quartz-feldspar matrix; (ii) preferred orientation of euhedral feldspar crystals in an igneous matrix; and (iii) evidence of moderate-to high-temperature of solid-state deformation (>500 °C). These microstructures and field observations point to a continuum of deformation, from the (sub) magmatic state down to sub-solidus conditions. Dating of three types of granitoids out of four gives ages of 2754 ± 2.2 Ma, 2752 ± 5.7 Ma and 2745 ± 3 Ma. The different granitoid varieties of the Vila Jussara suite were thus emplaced simultaneously. It is proposed that emplacement of the granitoids was controlled by shear zones reactivated during oblique collision and that plutons where constructed by multiple injections of magmas, generating extensive hybridization.