摘要
A comprehensive mineralogical-geochemical and petrological study of ignimbrites from the Yakut-Gora volcanic depression （Primorye, Far Eastern Russia） revealed a wide distribution of silica-metal spherules （＂globules＂） that are typical liquid immiscibility resultant. The metallic portion of a spherule （composition varies from low-carbon iron to cohenite） borders gas pores and is rimmed by symplectite that consists of quartz, magnetite, and silica-potassic glass. This allows us to consider that the whole formation formed through reduction of the enclosing silicate melt. Abundant evidence of high reduction states of ignimbrite melts and the presence of iron carbides suggest an H2-CH4 composition of the fluidal phase in ignimbrite magmas.
A comprehensive mineralogical-geochemical and petrological study of ignimbrites from the Yakut-Gora volcanic depression （Primorye, Far Eastern Russia） revealed a wide distribution of silica-metal spherules （＂globules＂） that are typical liquid immiscibility resultant. The metallic portion of a spherule （composition varies from low-carbon iron to cohenite） borders gas pores and is rimmed by symplectite that consists of quartz, magnetite, and silica-potassic glass. This allows us to consider that the whole formation formed through reduction of the enclosing silicate melt. Abundant evidence of high reduction states of ignimbrite melts and the presence of iron carbides suggest an H2-CH4 composition of the fluidal phase in ignimbrite magmas.
基金
supported by the DVO Russian Academy of Science (No. 09-Ⅲ-А-08-401)
