The 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
We present the results of a geochronological investigation that was conducted on mafic rocks (dolerites) that form two giant dyke swarms in NE Brazil, whose intrusion was correlated to the break-up of the West Gondwana supercontinent and the opening of the Atlantic Ocean. Despite their impressive dimensions, these swarms lack any geological information, which motivated us to develop a speedy, low-cost analytical protocol, modified from the Cassignol unspiked K–Ar technique, to define age patterns. The results were interpreted in light of basic statistical treatments and, although some limitations were mostly related to grain-size heterogeneities, they successfully matched other 40K-based ages (conventional K–Ar and 40Ar/39Ar) reported in the literature and showed that the dyke swarms share two main age intervals of rock formation identified as the Early Cretaceous and Late Jurassic.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.