Physical and chemical characteristics and eruptive model for the Santa Maria-type rhyolites in the Gramado Xavier region, Paraná Magmatic province

Abstract

The present project aims to contribute to a better understanding of the volcanology of the acid volcanism in the Paraná Magmatic Province aiming the development of a volcanic model for the Santa Maria Volcanic Sequence in the Gramado Xavier region. The rhyolitic magmatism amounts to about 2.5% of the volume of lavas in the province, and has some characteristics unlike those of typical rhyolitic magmas (e.g. eruptive temperatures as high as 1000°C), which appear to have resulted in an unique type of volcanic manifestation.Detailed field (structural geology) and laboratory (petrography, mineral and whole rock geochemistry; Sr isotope analyses) studies will be used in conjunction to better estimate the physical and chemical characteristics of the magmas, and thus give support to models of the eruptive style of these rocks, which are still highly controversial in the literature.