Parental Melts and Magma Storage of a Large-volume Dacite Eruption at Vetrovoy Isthmus (Iturup Island, Southern Kuril Islands): Insights into the Genesis of Subduction-zone Dacites

S. Z. Smirnov, A. V. Rybin, N. N. Kruk, T. Y. Timina, E. N. Sokolova, D. V. Kuzmin, I. A. Maksimovich, A. A. Kotov, A. Y. Shevko, I. R. Nizametdinov, A. Abersteiner

Результат исследования: Научные публикации в периодических изданияхстатья

Аннотация

Detailed mineralogical and melt and fluid inclusion constraints on magma storage, and the evolution of melts, are presented for the large-volume caldera eruption on the Vetrovoy Isthmus on Itutrup Island (Kuril Islands, Russia). The shallow magma reservoir beneath the Vetrovoy Isthmus is composed of a mush of plagio-rhyolitic melt, phenocrysts and the products of peritectic reaction(s). The melt appears to have formed as a result of partial melting of previously erupted rocks, which probably had andesitic to basaltic compositions and were metamorphosed into amphibole-bearing assemblages. The breakdown of amphibole in the partially melted precursor rocks led to the formation of early Mg-rich clino-and orthopyroxene, along with plagioclase and Fe-Ti oxides, and the release of aqueous fluids. Variations in fluid pressure are recorded by a strong increase of An contents in plagioclase. Crystallization took place at around 850°C with pressure ranging from 0·9 to 3 kbar. This study demonstrates that dacitic magmas erupted during the course of a 20 kyr voluminous eruption were the result of mixing between plagio-rhyolitic partial melts and the breakdown reaction minerals (i.e. pyroxenes, plagioclase and Fe-Ti oxides). Plagioclase and quartz were the last minerals to crystallize from these melts prior to eruption.

Язык оригиналаанглийский
Страницы (с-по)1349-1370
Число страниц22
ЖурналJournal of Petrology
Том60
Номер выпуска7
DOI
СостояниеОпубликовано - 1 июл 2019

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