Basaltos da Suíte Parapuí, Gráben Jaibaras, noroeste do Ceará: caracterização, petrografia, geoquímica e química mineral

The Parapui Suite is na important volcanic unit of the Jaibaras Graben, northwestern Ceara and represents an intense basalt volcanic activity during the Neoproterozoic/Eopaleozoic. Three main sequences are identified including basalts (labradorite/andesine basalts, trachybasalts and magnetite-ilmenite basalts), rhyolites and volcanoclastic rocks that occur intercalated with arkosian sandstones of the Jaibaras Group. The basalts and trachybasalts are the most abundant rock types in this Suite and occur as successions of large massive and amigdaloidal lava flows. They are holocrystalline or hypocrystalline, porphyritic or aphyric with flow structures. The main minerals are labradorite/andesine, titanoaugite and minor olivine, albite, sanidina, magnetite/ilmenite, pirite, titanite and apatite. The chemical signature is characterized by high contents of alkalis, TiO 2 and P 2 O 5 , and enrichement in LREE with small negative Eu anomalies, high to moderate (La/Yb) N and (Ti/Y) N > 1. In discriminant diagrams they plot in the alkaline basalt and transitional to tholeitic fields. The tectonic setting is suggestive of an intraplate continental magmatism. Petrographic, geochemistry and field characteristics and discriminant diagrams define the basalts of Parapui Suite as result of an transitional basaltic series and their tectonic setting as continental within-plate.