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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Effusive silicic volcanism in the Parana Magmatic Province, South Brazil: Physico-chemical conditions of storage and eruption and considerations on the rheological behavior during emplacement

Texto completo
Autor(es):
Polo, L. A. [1, 2] ; Giordano, D. [2, 3] ; Janasi, V. A. [1] ; Guimaraes, L. F. [1]
Número total de Autores: 4
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Inst Geociencias, Rua Lago, 562 Cidade Univ, BR-05508080 Sao Paulo, SP - Brazil
[2] Univ Turin, Earth Sci Dept, Via Valperga Caluso 35, I-10125 Turin - Italy
[3] Italian Natl Res Council CNR, Inst Geosci & Earth Resources IGG CNR, Pisa - Italy
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Fonte: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH; v. 355, n. SI, p. 115-135, APR 15 2018.
Citações Web of Science: 8
Resumo

Expressive occurrences of effusive deposits were identified in silicic units from the Parana Magmatic Province outcropping in a key area in south Brazil where three units with different compositions occur (Caxias do Sul dacites, CSd, Barros Cassal andesites to dacites, BCs, and Santa Maria rhyolites, SMr). Textural and chemical characteristics of phenocrysts, microphenocrysts and microlites suggest that crystallization started in a shallow magma chamber and continued during ascent to the surface. These magmas had an unique character (e.g., very high temperatures similar to 1000 degrees C and low H2O contents similar to 1-2 wt%), and formed several types of deposits that are clearly indicative of locally fed lava flows and had physical properties consistent with this mode of eruption (e.g., viscosities as low as 10(4.2) Pa.s at ca. 1000 degrees C for the CSd). The very low estimated H2O contents are a consequence of their petrogenesis (i.e., fractionation from tholeiitic basalts plus assimilation of crustal melts from water-poor granitic sources), and was probably a key factor influencing the non-explosive nature of these deposits. The comparatively higher viscosity calculated for the Santa Maria rhyolite (>1-2 orders of magnitude greater than CSd) would make it a better candidate to generate expressive pyroclastic deposits, but this might be offset by its remarkably low H2O contents (<= 1 wt%) and low discharge ratios. (C) 2017 Elsevier B.V. All rights reserved. (AU)

Processo FAPESP: 12/06082-6 - A província magmática Paraná-Etendeka no Brasil: relações temporais e petrológicas entre o magmatismo toleítico e alcalino e suas implicações geodinâmicas
Beneficiário:Excelso Ruberti
Linha de fomento: Auxílio à Pesquisa - Temático