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Experimental simulation of the conditions of formation of silicic volcanic rocks in the Paraná Magmatic Province: a contribution of the Brazilian experimental petrology to the modern volcanology

Grant number: 17/15540-1
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): March 01, 2018
Status:Discontinued
Field of knowledge:Physical Sciences and Mathematics - Geosciences
Principal Investigator:Valdecir de Assis Janasi
Grantee:Liza Angélica Polo
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:12/06082-6 - The Paraná-Etendeka magmatic province in Brazil: temporal and petrologic relationships between the tholeiitic and alkaline magmatism and geodynamic implications, AP.TEM
Associated scholarship(s):19/13193-8 - Decompression experiments in rhyolitic melts at high temperatures, low water: application to the Paraná volcanism, BE.EP.PD

Abstract

The silicic volcanic deposits from the Paraná Magmatic Province (PMP) have aroused great attention of the international scientific community, due to their unusual volcanological characteristics, which in part derive from distinctive physico-chemical properties, such as high T (1000ºC), low H2O content (<2%) and moderate viscosities (104-107 Pa.s). Several recent studies have suggested hybrid eruptive activities (i.e. effusive and explosive) with lava and domes related to pyroclastic deposits of low explosivity. The understanding of the magma ascent history is essential to quantify the physical properties of magma and know the mechanisms that controlled the eruption. According to the recent literature, the water exsolution driven by the decompression during magma ascent induce the crystallization of microlites. Therefore, the experimental study of the relationship between decompression and microlite crystallization in natural samples will allow us to obtain fundamental information to understand the dynamics of silicic magmas ascent, their rheology and their effects on the eruption. A new experimental petrology apparatus nominated TZM (Titanium Zirconium Molybdenum) Pressure Vessel has just been acquired and installed at the Instituto de Geociências, Universidade de São Paulo. This system, unique in Latin America, allows to perform crystallization experiments simulating conditions of the upper continental crust at P <400 MPa and T <1100ºC, and is therefore, the most suitable to simulate the conditions of the PMP silicic magmas ascent, under isothermal decompression or isobaric cooling effects. The proposed experimental grid intends to reproduce in the laboratory, the physico-chemical conditions (T, P, % H2O and ’O2) required for crystallization and/or stabilization of the main crystalline phases in the pre- and sin-eruptive stages. The project, developed with the collaboration of high-level international experimental petrology laboratories in Italy and Germany, will contribute to the consolidation of the new Brazilian laboratory, and will bring important contributions to modern volcanology.