The Magma Feeding System of the Klyuchevskaya Group of Volcanoes (Kamchatka)
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ANOLOGY
The Magma Feeding System of the Klyuchevskaya Group of Volcanoes (Kamchatka) Academician E. I. Gordeeva, b,*, Corresponding Member of the RAS I. Yu. Koulakova, c, and N. M. Shapirob,d Received April 22, 2020; revised May 21, 2020; accepted May 22, 2020
Abstract—Using observations from a large-scale seismic station network, we built a seismic tomography model of velocity anomalies for longitudinal (P-wave) and transverse (S-wave) seismic waves beneath the Klyuchevskaya group of volcanoes. The observational network (about 150 km) and the number of seismic stations (about 200) made it possible to determine the velocity structure to depths of 150 km. A low-velocity anomaly is observed almost beneath all volcanoes in the Klyuchevskaya group of volcanoes at a depth of 50 km. Beneath the Shiveluch volcano, in the region where the subduction plate discontinues, an anomaly can be detected to depths of 150 km. Most likely, in this zone, there is a channel for the penetration of magmatic melts to the surface along the boundary of the submerging Pacific Plate ending. This is indirectly confirmed by the presence of a mantle plume to a depth of 1000 km, as previously shown by the seismic tomography studies and an anomalous heat flow at the junction of the Kuril–Kamchatka and Aleutian island arcs. Keywords: Seismic tomography, magmatic source, Klyuchevskaya group of volcanoes, subduction DOI: 10.1134/S1028334X20080085
In subduction zones, volcanism is characterized by a complicated mechanism of magmatic feeding. A volcano feeding system involves a multilevel system of magma chambers in the crust and upper mantle. Previous studies provided insight into the detailed structure of the medium to depths of 30 km for the Klyuchevskaya group of volcanoes [1–4]. For the Klyuchevskoi volcano, several magma chambers were detected on different levels of the crust. A significant volume of magmatic melts was revealed at a depth of 30–35 km on the crust–mantle boundary. These melts are the main feeding source for the Klyuchevskoi and Bezymyannyi volcanoes. According to long-term observations, heightened seismic activity is observed in this zone. This is due to the impact of magmatic melts and fluids on the surrounding solid medium. aInstitute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences, Petropavlovsk-Kamchatsky, 683006 Russia bSchmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, 123995 Russia cTrofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk, Russia dInstitute Earth Sciences, CNRS, University Grenoble-Alpes, Grenoble, France *e-mail: [email protected]
The feeding system of the Klyuchevskoi volcano is a vertical channel. However, for the Bezymyannyi volcano, the long-lived magmatic volume [3] was established at shallow depths, where, most likely, magmatic melts are differentiated with a subsequent eruption of lighter andesite magmas. Previous studies provided seismic tomographic models of the medium structu
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