Paralavas in the Cretaceous Paraná volcanic province, Brazil - A genetic interpretation of the volcanic rocks containing phenocrysts and glass

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 (>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.

Successive off take of elements by maize grown in pure basalt powder

“…Offtake of manganese, boron, copper, and zinc showed a similar trend when normalized (Figures 4 and 5), although were taken up in different proportions by plants. Krahl et al 237 The micronutrients Mn, B and Zn are present indistinctively in all primary minerals that compose this basalt, especially diopside (Moraes et al, 2018), while Cu is accumulated in smectite structure, formed by hydrothermal process (Baggio et al, 2016).…”

Crono-correlação entre as Bacias do Camaquã (RS) e do Itajaí (SC): implicações Paleoambientais e Paleogeográfica

“…Em contraste com complexos de injeção em bacias petrolıferas, o CNH foi formado em ambiente vul-cânico intraplaca, tornando a relação dos arenitos com as rochas vulcânicas um caso único nos continentes. Os processos de for-mação de paralavas (Baggio et al, 2016) a 1000-1800 C não serão abordados.…”

Bacia de Pelotas em retrospectiva

“…Em contraste com complexos de injeção em bacias petrolıferas, o CNH foi formado em ambiente vul-cânico intraplaca, tornando a relação dos arenitos com as rochas vulcânicas um caso único nos continentes. Os processos de for-mação de paralavas (Baggio et al, 2016) a 1000-1800 C não serão abordados.…”