Low titanium magmatism in northwest region of Paraná continental flood basalts (Brazil): volcanological aspects.

The early Cretaceous Paraná Continental Flood Basalts (PCFB) is considered as one of the largest volcanic provinces in the world. In Brazil, it completes the last sequence of the sedimentary Paraná Basin (Serra Geral Fm.). The geological unit is contemporary to desert sandstones of Botucatu Fm. and precedes the continental sediments of the Bauru Basin. This Large Igneous Province (LIP) is divided into different types of geochemical magmas which basically are based on TiO₂ content (higher - HTi or lower LTi than 2 wt.% in TiO₂) and incompatible trace elements ratio. Therefore, we studied the magma LTi (TiO₂ <2.0 wt.%), denominated Ribeira which occurs in the northwestern portion of PCFP which is poorly researched mainly in volcanological and geochemical aspects. This basaltic magma, a short expression in PCFB, occurs in the form of multiple pahoehoe flows with thicknesses ranging from 1.5 to 30m in compound type flows under low surface slope. Peperites zones are common when associated with the first flows, and sand-filled cracks in the lower and upper edges at all pahoehoe levels when in contact with the sediment. Upward these first sequences of interactions with sediment, on the inside direction basin, simple pahoehoe flows occur being associated with Pitanga magma type (HTi, with TiO₂ >2.0 wt.%). Based on rheology data considering anhydrous environment and the composition of plagioclase (An42-67) and clinopyroxene (Wo_(30-40)En_((34-46)(Fs_((17-32)() showed that the LTi magma is hotter than HTi, with temperatures that range from 1069 °C to 1248 °C while for the second range from 1020 °C to 1201 °C. [ABSTRACT FROM AUTHOR]