TY - JOUR

T1 - Parental Melts and Magma Storage of a Large-volume Dacite Eruption at Vetrovoy Isthmus (Iturup Island, Southern Kuril Islands)

T2 - Insights into the Genesis of Subduction-zone Dacites

AU - Smirnov, S. Z.

AU - Rybin, A. V.

AU - Kruk, N. N.

AU - Timina, T. Y.

AU - Sokolova, E. N.

AU - Kuzmin, D. V.

AU - Maksimovich, I. A.

AU - Kotov, A. A.

AU - Shevko, A. Y.

AU - Nizametdinov, I. R.

AU - Abersteiner, A.

PY - 2019/7/1

Y1 - 2019/7/1

N2 - 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.

AB - 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.

KW - caldera

KW - explosive eruption

KW - fluid inclusions

KW - Iturup Island

KW - Kuril Islands

KW - melt inclusions

KW - PLAGIOCLASE

KW - CRYSTALLIZATION

KW - VOLCANIC-ROCKS

KW - TRACE-ELEMENT

KW - ORIGIN

KW - CALC-ALKALINE DIFFERENTIATION

KW - DEHYDRATION

KW - WATER-CONTENT

KW - SILICATE-GLASSES

KW - PHASE-RELATIONS

UR - http://www.scopus.com/inward/record.url?scp=85073626899&partnerID=8YFLogxK

U2 - 10.1093/petrology/egz032

DO - 10.1093/petrology/egz032

M3 - Article

AN - SCOPUS:85073626899

VL - 60

SP - 1349

EP - 1370

JO - Journal of Petrology

JF - Journal of Petrology

SN - 0022-3530

IS - 7

ER -