Tonian juvenile arc crust provenance recorded in the Paraná Basin, Western Gondwana proto-Andean margin

Abstract

A provenance study through petrography, whole-rock geochemistry, and zircon U-Pb-Th and Lu-Hf systematics suggests that the lowermost strata of the Paraná Basin (460–380 Ma) record a recycled orogen provenance with mixing trend between mature polycyclic quartzose detritus and mafic/intermediate contributions. Sources with felsic compositions are indicated by the Lower Paraná Group, as it is suggested by the relative enrichment of Zr/Y, Th/Sc, and Y/Sr ratios. Meanwhile, the Iapó Formation received additional contributions from Archean mafic/intermediate plagioclase-rich sources (Eu* = 0.81). The Tonian juvenile (900–800 Ma) detrital zircon population from the Pre-Carboniferous strata with εHf(t) ranging from +3 to +11, in additional, late-Tonian population with an important crustal component (εHf(t) ranging from −12 to −8), provide evidence that the Ribeira Fold Belt constitutes the primary sedimentary source for the lowermost strata. Juvenile early-Tonian (950–900 Ma) and middle-Tonian (810–750 Ma) detrital zircon population suggests an additional provenance derived from the São Gabriel Domain, located at the southern border of the basin. Late-Ediacaran to early-Cambrian detrital zircon population suggest sources from the Eastern Pampean Range whereas a restricted detrital zircon population younger than 500 Ma with εHf(t) signatures ranging from 3 to −32, is consistent with a provenance from the Famatinian magmatic arc and associated rocks. In contrast to the detrital zircon population from the Pre-Carboniferous strata, the Itararé Group (∼310 to 298 Ma) reveals juvenile Ordovician sources (εHf(t) ranging from −2 to +2) and a restricted population encompassing both evolved and juvenile sources with a “Grenvillian” signature.