Geology of the Neoarchean-Rhyacian Supracrustals of the Northern Intracontinental Sector of the Ara?uaí Orogen: Evidence for Overlapping Basins

摘要

? 2022 Elsevier LtdThe northern region of the intracontinental sector of the Ara?uaí Orogen preserves geological records related to overlapping basins and tectonic reactivations between the Mesoarchean to the Cryogenian. The representatives are the metavolcanosedimentary sequences (i) Leandrinho (LMVS), here defined, that intercalates aluminous schists (metapelite), metagreywackes, acid metatuffs, and metalapillites, with a crystallization age of 2550 ± 2 Ma and; (ii) Rio S?o Jo?o (RSJMVS), with metagreywackes and metarkoses, metapelites, metarhytmites, itabirites, hematite-schists, and schistified mafic-ultramafic metavolcanics, presenting maximum depositional ages of 2280 ± 46 and 1971 ± 50 Ma for the Ibiassucê and água Branca units, respectively. The metavolcanics of the LMVS are mainly subalkaline, sodic, magnesian, metaluminous to peraluminous, and of continental arc setting, with chemistry similar to TTG correlates. One sample has a chemical composition similar to that of sanukitoids. The model age (TDM) varies between 3003 and 3074 Ma and ?Nd between ?5,06 and ?5,84. In the SMRSJ, schistified metamafics, metagreywackes and metarkoses, and metapelites present chemical signature and geological context associated with a continental arc setting. These siliciclastic rocks have a model age (TDM) between 2618 and 3069 Ma, with ?Nd between ?2,70 and ?9,21. The entire sequence of the Ara?uaí-West Congo intracontinental sector was deformed and metamorphosed during the Ediacaran, generating a prominent gneissic banding that embeds the sequences. The main point of the paper is the description of the previously unrecognized Leandrinho metavolcanosedimentary sequence (LMVS). Subordinately, to demonstrate the superposition of two basin-forming events, at the end of the Neoarchaean and during the Rhycian/Orosirian.