Archean sodic metagranitoids from the Southern São Francisco Craton: Review, petrogenesis, and tectonic implications

Abstract Gray gneiss complexes comprise most of the Archean crust in the Southern Sao Francisco Craton and its surroundings, and their metagranitoid components can be distinguished using their petrological and geochemical attributes through time. This work discusses new and compiled geochemical and geochronological data of strikingly variable sodic metagranitoid types aiming to understand geodynamic-induced geochemical shifts. The sodic metagranitoids were divided into six geochemical types: low and high HREE (heavy rare earth elements) TTGs, medium-K metagranitoids 1 and 2, sodic sanukitoid-like metagranitoids, and HFSE-rich (high field strength elements) ferromagnesian metagranitoids. The low-HREE TTGs have higher Al2O3, Na2O, Sr, Sr/Y, LaN/YbN, and Eu anomaly (mostly neutral) values, lower Y and HFSE, and shorter silica range than the high-HREE TTGs. Such distinction reflects partial melting under diverse pressure conditions and/or different amounts of water and/or fractional crystallization processes. Four magmatic pulses of sodic metagranitoids, within 3.36–3.17, 3.07–3.00, 2.96–2.85, and 2.80–2.75 Ga, were identified in the Southern Sao Francisco Craton. The oldest TTG in this cratonic segment is disclosed here, a 3.26 Ga high-HREE TTG in the Sao Tiago Complex formed during the 3.36–3.17 Ga event identified in most of the metamorphic complexes. The 3.07–3.00 and 2.96–2.85 Ga events were dominated by TTGs and have built the extensive metamorphic complexes across the Southern Sao Francisco Craton and the basement of the adjoining Brasilia Orogen. Both low- and high-HREE TTGs have prevailed until being progressively outnumbered by enriched sodic metagranitoids between 2.8 and 2.7 Ga. These are represented by: (i) medium-K metagranitoids 1 and 2 (e.g. Florestal batholith in the Belo Horizonte Complex), faintly sodic rocks (0.5