The Borborema province (NE Brazil) Neoproterozoic magmatic arcs: A review of geochemical and isotopic data of granitic rocks

The Borborema Province in NE Brazil is assumed to have been formed by Cryogenian-Ediacaran convergent events during the assembly of western Gondwana. Among the many geological markers of such episodes, the granitic record is widespread, representing the best testimony of the Brasiliano-Pan African Orogeny that took place between 800 and 500 Ma. Several granitic batholiths and stocks are interpreted as root remnants of arc edifices that grew during the consumption of large tracts of oceanic crust, such as the Goiás-Pharusian and Transordestino-Central África realms. Most of them share geochemical signatures that are typical for subduction-related magmas, such as enrichment in large-ion lithophile elements, aligned with depletion in high-field strength elements, including negative anomalies in Nb, Ta, P, and Ti, as well as systematic plots consistent with convergent-related settings in classical tectonic discrimination diagrams. The older record is represented by the Lagoa Caiçara unit (ca. 880-800 Ma) of the Santa Quitéria magmatic arc of the Northern Subprovince, interpreted as relics of an intra-oceanic setting, responsible for lithospheric growth in the region. A subsequent magmatic episode is marked by the injection ca. 650-620 Ma cordilleran and peraluminous magmas that formed a large set of batholiths and stocks in the Santa Quitéria and Conceição (Transversal Subprovince) magmatic arcs, as well those related to the Pernambuco-Alagoas Terrane and Sergipano Belt in the Southern Subprovince. Rocks crystallized in this age interval share similarities with those of the calc-alkalic and alkali-calcic series, interpreted to have been emplaced in the continental crust via upper mantle melting and subsequent crustal contamination. Finally, rocks aged between ca. 620-550 Ma are widespread and represent high-K, meta-to peraluminous and alkali-calcic precursor magmas, that also share geochemical similarities with S-type granites (crustal anatexis), being interpreted as syn-collisional with respect to the final assembly of Gondwana. The final framework of the Borborema Province is marked by extrusion tectonics that is materialized by the complex network of shear zones deforming the previous formed granites and injecting of non-subduction related melts. Although there is a lack of consensus regarding the assembly of the province during the Neoproterozoic, we suggest that accretionary-collisional events played a major role, as testified by the geochemical-isotopic signature of the arc-related granites, in addition to a number of structural, geophysical, and geological mapping data published in the recent years.