Petrology of Jurassic and Cretaceous basaltic formations from the Parnaíba Basin, NE Brazil: correlations and associations with large igneous provinces

Abstract

AbstractThe basaltic Mosquito and Sardinha formations in the Parnaíba Basin are related to the opening of the Atlantic Ocean at the Triassic–Jurassic boundary and in the early Cretaceous, respectively. The Mosquito Formation consists of tholeiitic flows with both high-Ti (>1.5 wt%) and low-Ti (<1.5 wt%) compositions and the petrogenetic characteristics of enriched mantle reservoirs. The Mosquito Formation basalts have an initial 87Sr/86Sr isotopic composition of 0.70296–0.70841 and a low Nd isotopic composition (0.512245–0.512677) associated with an enrichment in large ion lithophile and high field strength elements relative to primitive mantle compositions. The Sardinha Formation is composed of high-Ti and low-Ti tholeiitic dykes with subordinate alkali basalts. The Sardinha Formation rocks have trace element and isotopic features associated with enriched mantle end-members. The initial isotopic compositions range from 0.702859 to 0.706703 and 0.512184 to 0.512671 for 87Sr/86Sr and 143Nd/144Nd, respectively. The concentrations of large ion lithophile and high field strength elements are elevated relative to primitive mantle values. Although the Mosquito and Sardinha formations share some similarities, they can be differentiated by their unique petrographic characteristics and trace element concentrations. These differences allow the discrimination of the basaltic magmatism in the Parnaíba Basin and their association with large igneous provinces, such as the Central Atlantic Magmatic Province or the Paraná–Etendeka Magmatic Province.Supplementary material: Microprobe analyses for clinopyroxene (Table A1), plagioclase (Table A2) and olivine (Table A3) for the Mosquito and Sardinha formations, along with mixing calculation parameters for the geochemical model (Table A4) are available at: https://doi.org/10.6084/m9.figshare.c.3985437