Contribution to petrogenesis of the Paleoproterozoic Basaltic Magmatism from the Arai continental rift, central Brazil

The Paleoproterozoic Arai continental rift, Central Brazil, hosts metabasaltic lava flows interbedded with a thick transgressive metasedimentary sequence at the basal portion of the Arai Group (Arraias Formation). The lava flows have basalt to basaltic andesite compositions, subalkaline, tholeiitic and within-plate geochemical signatures. These rocks still have low to moderate REEs content, negative Ta, Ti, Nb anomalies, higher La/Nb (2.69-5.06) and lower La/Ba (0.03-0.23) ratios, suggesting some degree of contamination. Isotopic geology data presented in this paper revealed zircon U-Pb crystallization age of 1783 +/- 17 Ma, with a significant frequency of inherited zircon from Rhyacian (2221 +/- 14 Ma), negative epsilon Nd (t) = -4.46 to -6.58, Nd T-DM model age from 2.49 to 2.72 Ga and Sr-87/Sr-86(i) = 0.702400-0.708293. The epsilon Nd-(t) vs Nb/La and epsilon Nd-(t) vs Sr-87/Sr-86 diagrams suggest low to moderate contamination rate, linked to interactions of the plume-derived magmas with the subcontinental lithospheric mantle and the Archean-Paleoproterozoic continental old-crust, during to ascent and intrusion episodes, respectively. These new data are nicely correlated with the available isotopic data (U-Pb, Sm-Nd, Sr-Sr) on the acid volcanic and A-type granites from the basal portion of the Arai rift, indicating an important bimodal magmatic event, with volcano-plutonic characteristics, occurred during the continental synrift stage.