Geochemical and temporal provinciality of the magmatism of the eastern Parnaíba Basin, NE Brazil

Abstract

Abstract This paper presents new field, petrographic, geophysical, geochemical and geochronological data for the felsic and mafic magmatism of the eastern Parnaíba Basin, integrating previously published data with new surface data acquired within the scope of the Cooperation Program developed by UERJ-Petrobras. New precise 40 Ar– 39 Ar Cambrian ages ( c. 508–506 Ma) were obtained for the felsic volcanic to subvolcanic rocks associated with intracontinental rift sediments in the São Raimundo Nonato area in the SE of the basin. The new results include the detection of three different basic magmatic pulses at c. 181, 126 and 118 Ma, related, respectively, to Central Atlantic Magmatic Province magmatism, the Sardinha large igneous province and the break-up period for the equatorial basins. The eastern side of the basin contrasts with the western side and shows a predominance of outcropping sills of Sardinha age. Most of these rocks are quartz tholeiites, but two samples ( c. 118 Ma) are olivine tholeiites. This paper provides the first description of a clear chemical provinciality of the Sardinha tholeiitic magmatism in the eastern Parnaíba Basin, similar to that described in the Paraná Basin. Low-TiO 2 suites, independent of age, occur on the northwestern side of the Senador Pompéu–Coccoci lineament, whereas high-TiO 2 suites, including the Ceará Mirim dyke swarm in the basement to the east, are located SE of this lineament. The duality of geochemical signatures reproduces the basement signatures of the opposite sides of the Senador Pompéu suture zone, suggesting, at least in part, that the composition of the sub-lithospheric continental mantle of these two domains played a part in the development of Cretaceous magmatism in the Parnaíba Basin. Supplementary material: Geophysical and geochemical data provided by Petrobras and subsequent analysis. Supplementary material available online at https://doi.org/10.6084/m9.figshare.c.4117985