Flow and fragmentation patterns in the silicic feeder system and related deposits in the Paraná-Etendeka Magmatic Province, São Marcos, South Brazil

The silicic volcanism can be summarized at an early pyroclastic stage, characterized by rheoignimbrites and proximal volcanic breccias. A transition between explosive and effusive events is suggested by the occurrence of hybrid deposits, which gradually give place to lobated lavas. Local alternation with new (possibly) rheoignimbritic deposits suggests oscillatory fragmentation processes at the conduit, related to decompression and volatiles exsolution in an effective permeable system.