Geology, U-Pb geochronology, and petrological affinity of peraluminous granitoids in Carajás Province, SE Amazonian Craton

Résumé fourni par la source

Peraluminous magmatism records crustal reworking processes and provides important information about the evolution of continental crust. Peraluminous granitoids are uncommon in Archean geology, reflecting the unusual nature of processes at the time. In this context, the Vila Minerasul area in central-western Carajás Province contains a complex geological framework comprised of multiple granitoid plutons with distinct petrogenetic affinities. The main pluton has biotite as its main ferromagnesian mineral and is distinguished by the presence of primary muscovite as a varietal phase. This pluton is elongated in an E-W direction, covering an area of approximately 75 km 2 and delineated by shear zones. It comprises three lithological facies: muscovite-biotite granodiorite, biotite-muscovite granodiorite, and muscovite-biotite monzogranite. Deformational microstructures reveal the syntectonic character of this pluton, which has zones of low and high strain and deformation temperatures ranging from 300 to 600 °C. The rocks are magnesian, calc-alkaline, and highly peraluminous (A/CNK >1.1). They present low HFSE and high LILE contents and a slight negative Eu anomaly. Compared to the main granitoid units of the Carajás Province, the peraluminous pluton of Vila Minerasul has a stronger affinity for potassic granites, differing by its higher A/CNK values. The crystallization age of this pluton is 2918.5 ± 5.1 Ma, although zircon populations between 2.94 Ga and 3.17 Ga are thought to be inherited. Two younger populations (2888.2 ± 6.7 Ma, 2839 ± 10 Ma) are thought to be rejuvenated metamict ages or regional metamorphic overprints. These rocks are considered to have formed in a collisional environment, with petrogenesis involving partial melting of TTG crust and the incorporation of metasedimentary components.

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