Defining sedimentary degassing from large igneous provinces related and unrelated to mass extinction

Abstract

A temporal coincidence between Continental Flood Basalts (CFB) emplacement and global environmental changes suggests that volcanic emissions can have an important effect on atmospheric composition. It is highly probable that magmatic degassing is an insufficient killer mechanism, and an important additional volatile flux should be provided by an alternative source as outgassing through contact metamorphism. Actually, the degassing through magma-sediment interactions is believed to represent a significant part of the total volatile budget. Brazil hosts one of the world's most expressive CFBs associated with the breakup of the Gondwana Supercontinent and the opening of the Atlantic Ocean, the Paraná-Etendeka Magmatic Province (PMP), and rather than global warming, the Cretaceous LIPs coincide with the three cold snaps that marked the greenhouse period. The confirmation or refusal of the role played by the PMP on the contemporaneous environmental shifts relies on the ability to provide information on the original volatile contents for both sources: the volcanism itself and those released during magma-sediment interactions. The experiments that will provide synthetic fluid inclusions directly resulted from the sedimentary degassing could provide valuable arguments about the real role of sedimentary degassing. Experiments will be performed in collaboration with Dr. Olivier Bachmann and Dr. Peter Ulmer at Federal Institute of Technology in Zurich (ETH) and for this powder samples of representative sedimentary formations (e.g. sandstones, carbonate-bearing rocks, and organic matter-rich shales) of both Paraná Basin (Paraná-Etendeka Magmatic Province) and Amazonas Basin (Central Atlantic Magmatic Province) will be used in the intention of in addition to providing the volatiles produced by thermal devolatilization, to compare 1) nature of the identified volatiles of PMP with those of extinction-related provinces and 2) the synthetic fluids formed through experiments and the natural fluid inclusions. The novelty and originality of the proposed activities have potential to elucidate questions related to why was the PMP's emplacement not coincident with a mass extinction event as suggested to have happened in other provinces worldwide. (AU)