TY - JOUR

T1 - Partial Melting under Shallow-Crustal Conditions: A Study of the Pleistocene Caldera Eruption of Mendeleev Volcano, Southern Kuril Island Arc

AU - Kotov, Alexey

AU - Smirnov, Sergey

AU - Nizametdinov, Ildar

AU - Uno, Masaoki

AU - Tsuchiya, Noriyoshi

AU - Maksimovich, Ivan

N1 - This research was supported by Japan–Russia Collaboration Research Project JPJSBP 120214802. The fieldwork was supported by RFBR grant 18-05-00819. Whole-rock geochemical analyses and SEM investigation were conducted within the assignment of the Sobolev Institute of Geology and Mineralogy SB RAS (Novosibirsk, Russia). Публикация для корректировки.

PY - 2023/6/1

Y1 - 2023/6/1

N2 - The southern part of the Kuril Island Arc is one of the world's most active modern volcanic zones, with widespread felsic caldera volcanism, but it has been less well studied compared with other arcs. The Mendeleev caldera-forming eruption (40 ka) on Kunashir Island, southern Kurils, is one of the most explosive Pleistocene eruptions to have occurred in this region. This study aimed to establish the origin and storage conditions of magma preceding the Pleistocene caldera eruption of Mendeleev volcano. Mineralogical and melt inclusion analyses reveal that the primary melts had felsic compositions and that the early stage of magmatic evolution involved amphibole breakdown into a two-pyroxene, plagioclase, and Fe-Ti oxide assemblage under pressure-Temperature conditions of 107-314 MPa and 807-932°C. The caldera-forming products are represented by dacitic pumice composed of plagioclase + augite + hypersthene+ quartz + Fe-Ti oxides and melt with uniform low-K rhyolite composition. Pre-eruptive magma was stored in a reservoir at 77-195 MPa (3.0-7.6 km depth) and 830-890°C under H2O-saturated conditions. The mechanism of magmatic evolution implies the following two-step scenario: (1) generation of magma by the partial melting of an amphibole-bearing substrate accompanied by the formation of early Mg-rich clino-and orthopyroxene, plagioclase, Fe-Ti oxides, and peritectic rhyolitic melt; and (2) crystallization of late plagioclase and quartz directly from these partial melts. Local or regional extension during the Pleistocene, accompanied by increasing heat flow in the supra-subduction mantle, generated an active mafic intrusion into the upper crust. This process was accompanied by abundant subaerial eruptions of basaltic volcanoes and could have caused intense heating and partial melting of upper-crustal rocks. Our results indicate that the partial melting of amphibole-bearing substrates in island arcs may serve as a universal mechanism for the generation of silicic magmas during powerful caldera eruptions in young island arcs.

AB - The southern part of the Kuril Island Arc is one of the world's most active modern volcanic zones, with widespread felsic caldera volcanism, but it has been less well studied compared with other arcs. The Mendeleev caldera-forming eruption (40 ka) on Kunashir Island, southern Kurils, is one of the most explosive Pleistocene eruptions to have occurred in this region. This study aimed to establish the origin and storage conditions of magma preceding the Pleistocene caldera eruption of Mendeleev volcano. Mineralogical and melt inclusion analyses reveal that the primary melts had felsic compositions and that the early stage of magmatic evolution involved amphibole breakdown into a two-pyroxene, plagioclase, and Fe-Ti oxide assemblage under pressure-Temperature conditions of 107-314 MPa and 807-932°C. The caldera-forming products are represented by dacitic pumice composed of plagioclase + augite + hypersthene+ quartz + Fe-Ti oxides and melt with uniform low-K rhyolite composition. Pre-eruptive magma was stored in a reservoir at 77-195 MPa (3.0-7.6 km depth) and 830-890°C under H2O-saturated conditions. The mechanism of magmatic evolution implies the following two-step scenario: (1) generation of magma by the partial melting of an amphibole-bearing substrate accompanied by the formation of early Mg-rich clino-and orthopyroxene, plagioclase, Fe-Ti oxides, and peritectic rhyolitic melt; and (2) crystallization of late plagioclase and quartz directly from these partial melts. Local or regional extension during the Pleistocene, accompanied by increasing heat flow in the supra-subduction mantle, generated an active mafic intrusion into the upper crust. This process was accompanied by abundant subaerial eruptions of basaltic volcanoes and could have caused intense heating and partial melting of upper-crustal rocks. Our results indicate that the partial melting of amphibole-bearing substrates in island arcs may serve as a universal mechanism for the generation of silicic magmas during powerful caldera eruptions in young island arcs.

KW - amphibole

KW - caldera eruption

KW - melt inclusion

KW - partial melting

KW - rhyolite

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85161983542&origin=inward&txGid=eea2782b6f49eb46fb2a245ceb4f94c8

UR - https://www.mendeley.com/catalogue/271c5403-fcac-3ff5-bca8-8116e43fe32c/

U2 - 10.1093/petrology/egad033

DO - 10.1093/petrology/egad033

M3 - Article

VL - 64

JO - Journal of Petrology

JF - Journal of Petrology

SN - 0022-3530

IS - 6

M1 - egad033

ER -