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Effusive silicic volcanism in the Parana Magmatic Province, South Brazil: Evidence for locally-fed lava flows and domes from detailed field work

Texto completo
Polo, L. A. [1, 2] ; Janasi, V. A. [2] ; Giordano, D. [3, 1] ; Lima, E. F. [4] ; Cation-Tapia, E. [5] ; Roverato, M. [2, 6]
Número total de Autores: 6
Afiliação do(s) autor(es):
[1] Univ Torino, Earth Sci Dept, Via Valperga Caluso 35, I-10125 Turin - Italy
[2] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, Cidade Univ, BR-05508080 Sao Paulo, SP - Brazil
[3] Italian Natl Res Council CNR, Inst Geosci & Earth Resources IGG CNR, Pisa - Italy
[4] Univ Fed Rio Grande do Sul, Inst Geociencias, Ctr Estudos Petrol & Geoquim, Av Bento Goncalves 9500, BR-91500000 Porto Alegre, RS - Brazil
[5] CICESE, Dept Geol, POB 434843, San Diego, CA 92143 - USA
[6] Yachay Tech Univ, Hacienda San Jose S-N & Proyecto Yachay, San Miguel De Urcuqui - Ecuador
Número total de Afiliações: 6
Tipo de documento: Artigo Científico
Fonte: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH; v. 355, n. SI, p. 204-218, APR 15 2018.
Citações Web of Science: 8

Lava flows and dome complexes of silicic composition were identified in the Lower Cretaceous Parana Magmatic Province (PMP) at Rio Grande do Sul state, southern Brazil. Detailed mapping and image analysis reveals significant volumes of effusive deposits aligned according to main lineaments, likely representing the fissural systems that fed the three Palmas-type silicic units. Different structures indicative of effusive emplacement (lava domes, lobated flows, sheet flows and autobreccias) are very common in the study area, and are probably also more abundant than previously thought in whole PMP silicic magmatism. In fact, effusive deposits seem predominant in the three distinct silicic units identified in the area, since no remnants of pyroclastic components have been identified. The vitreous dacites that make up the upper flows of the basaltic andesite to dacite Barros Cassal sequence are clearly effusive, as indicated by their occurrence as thin sheet flows. The much thicker early Caxias do Sul dacites occur mostly as lava flow lobes and pancake-like, of low to moderate viscosity, and lava domes. The younger, high SiO2 Santa Maria rhyolite unit shows unequivocal examples of effusive deposits at its lower portion, as lobated flows formed by vesicle-rich obsidian. In spite of higher viscosities relative to the previous units (similar to 10(6) Pa.s), it is probable that the very low H2O contents similar to 1 wt% of these rhyolite melts, associated with high discharge rates, resulted in an effusive nature in most to this unit. (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