Data/hora: 11/06/2024 19:03:38

Provedor de dados: | 42
País: | Brazil
Título: | Paralavas in the Cretaceous Paraná volcanic province, Brazil - A genetic interpretation of the volcanic rocks containing phenocrysts and glass
Autores: | BAGGIO,SÉRGIO B.; HARTMANN,LÉO A.; BELLO,ROSA M.S.
Data: | 2016-12-01
Ano: | 2016
Palavras-chave: | Paralava; Paraná volcanic province; Pyrometamorphism; Remelting; Metal remobilization.
Resumo: | ABSTRACT The occurrences of glassy rocks containing long and curved phenocrysts in the Paraná volcanic province, South America, are here interpreted as paralavas. The large number of thin (0.1-0.5 m) dikes and sills of glassy volcanic rocks with hopper, hollow or curved, large crystals of clinopyroxene (up to 10 cm), plagioclase (up to 1 cm), magnetite and apatite are contained in the core of thick (&gt;70 m) pahoehoe flows. They are strongly concentrated in the state of Paraná, coincident with the presence of the large number of dikes in the Ponta Grossa arch. These rocks were previously defined as pegmatites, although other names have also been used. A paralava is here interpreted as the product of melting of basaltic rocks following varied, successive processes of sill emplacement in high-kerogen bituminous shale and ascent of the resultant methane. As the gas reached the lower portion of the most recent lava flow of the volcanic pile, the methane reacted with the silicate and oxide minerals of the host volcanic rock (1,000 ºC) and thus elevated the local temperature to 1,600 ºC. The affected area of host rock remelted (possibly 75 wt.%) and injected buoyantly the central and upper portion of the core. This methane-related mechanism explains the evidence found in the paralavas from this volcanic province, one of the largest in the continents.
Tipo: | Info:eu-repo/semantics/article
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652016000602167
Editor: | Academia Brasileira de Ciências
Relação: | 10.1590/0001-3765201620150088
Formato: | text/html
Fonte: | Anais da Academia Brasileira de Ciências  v.88 n.4 2016
Fonte: | info:eu-repo/semantics/openAccess