Neoarchean reworking of TTG-like crust in the southernmost portion of the Sao Francisco Craton: U-Pb zircon dating and geochemical evidence from the Sao Tiago Batholith

Field, petrographic and geochemical data combined with in situ zircon U-Pb LA-ICP-MS ages are documented for the Sao Tiago Batholith (southernmost portion of the Sao Francisco Craton) to understand its origin and magmatic evolution. The geologic relations indicate that the batholith is composed of granitic to granodioritic orthogneisses (L2) with tonalitic xenoliths (L1) intruded by pegmatite (L3) and metagranite (L4). L1 consists of two fades of tonalitic orthogneiss, one biotite-rich, and the other biotite-poor. The geochemical evidence, including high K2O with mantle-like chemical signature, suggests that the Bt-rich tonalitic gneiss (2816 +/- 30 Ma) was derived from contamination of mafic magmas by crustal-derived components. The Bt-poor tonalitic gneiss, of TTG affinity, was generated by partial melting of LILE-enriched mafic rocks, possibly from oceanic plateus in a subduction environment. L2 includes two distinct types of rocks: (i) granodioritic orthogneiss, chemically ranging from medium-pressure TTGs to potassic granitoids originated via partial melting of previous TTG crust, including Ll Bt-poor; and (ii) granitic gneiss (2664 +/- 4 Ma), geochemically similar to crustal-derived granites, produced by melting of the Ll Bt-rich tonalitic gneiss or mixed TTG/metasedimentary sources. L3 pegmatite (2657 +/- 23 Ma) results from melting of L2, whereas L4 metagranite (dikes and stocks) shows petrogenesis similar to that of the L2 granitic gneiss. Related orthogneisses occur near the Sao Tiago Batholith: (i) a hornblende-bearing tonalitic gneiss, and (ii) a hybrid hornblende-bearing granitic gneiss (2614 +/- 13 Ma), whose genesis is linked with interaction of sanukitoid and felsic potassic melts, representing the last Archean magmatic pulse of the region. The Minas strata along the Jeceaba-Bom Sucesso lineament near our study region encircle the Sao Tiago Archean crust, representing an irregular paleo-coastline or a micro-terrane amalgamation with the Sao Francisco Proto-craton, with possible subsequent dome-and-keel deformational processes. Our petrological and geochronological data reevaluate nebulous concepts in the literature about the SFC, revealing (i) a chemically and compositionally diverse crustal segment generated at the Late Archean in diverse geodynamic scenarios, and (ii) a more complex lineament than previously thought in terms of the paleogeography of the southern Sao Francisco Craton.