Geology, petrology, and geochronology of 2.03 to 1.98 Ga arc magmatic granites from the Novo Mundo Complex: implications for the Amazonian Craton tectonic evolution

Abstract The Novo Mundo granitic Complex lies in the southernmost margin of the Amazonian Craton, Brazil. New petrological, geochemical, U–Pb and Sm–Nd isotopic data allow us to propose a new petrogenetic model for granite genesis in the southernmost portion of the Craton. Earlier studies attribute the complex to the Tapajós–Parima Tectonic Province. Four granitic facies have been identified: quartz monzonite, monzogranite, biotite granodiorite, and syenogranite, all of which are crosscut by diabase dikes. The monzogranite has primary muscovite. The biotite from the granites shares chemical signatures with that of volcanic arc settings. Petrographic data, mineral chemical, lithogeochemical, and isotopic data allow conclude that the Novo Mundo rocks into I-type, meta– to peraluminous, and calc–alkaline to alkali-calcic granites which are compatible with volcanic arc settings and varying degrees of crustal contribution. U–Pb LA–ICP–MS ages of magmatic zircons (quartz monzonite 2032 ± 6 Ma; monzogranite 2029 ± 4 Ma; biotite granodiorite 1989 ± 6.2 Ma; syenogranite 1987 ± 7.4 Ma) and TDM Nd model ages (2.52-2.15 Ga; ɛNd(t) = -2.0 to +1.81) indicate that the granites originated from either mantle-derived or juvenile Orosirian crustal melts, with additional continental crust input. The weak positive ɛNd(t) anomalies suggest an upwelling asthenospheric mantle that provided the thermal input to remelt the lower crust, as well as the isotopic data emphasize varying levels of crustal reworking during arc evolution. These ages are coeval with the evolution of the Paleoproterozoic Cuiú-Cuiú Magmatic Arc emplaced during the main stage of arc subduction in the region (2.05-1.99 Ga). The proposed evolutionary model suggests that quartz monzonite and monzogranite are associated with the early stages of arc evolution. The granodiorite records the contribution of juvenile sources, correlated with episodes of mafic magma influx, while the syenogranite represents the final stages of the arc formation, indicating a predominance of continental crustal contribution. The new data, combined with recent studies, allow us to suggest the existence of a Paleoproterozoic continuous magmatic arc into the south part of the Amazonian craton instead of the previously defined tectonic provinces previously defined in the literature.