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Abrupt transition from fractional crystallization to magma mixing at Gorely volcano (Kamchatka) after caldera collapse

Gavrilenko Maxim, Ozerov Alexey, Kyle Philip R., Carr Michael J., Nikulin Alex, Vidito Christopher, Danyushevsky Leonid (2016) Abrupt transition from fractional crystallization to magma mixing at Gorely volcano (Kamchatka) after caldera collapse // Bulletin of Volcanology. Vol. 78, No. 7. doi: 10.1007/s00445-016-1038-z.

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Official URL: http://doi.org/10.1007/s00445-016-1038-z

Abstract

A series of large caldera-forming eruptions (361–38 ka) transformed Gorely volcano, southern Kamchatka Peninsula, from a shield-type system dominated by fractional crystallization processes to a composite volcanic center, exhibiting geochemical evidence of magma mixing. Old Gorely, an early shield volcano (700–361 ka), was followed by Young Gorely eruptions. Calc-alkaline high magnesium basalt to rhyolite lavas have been erupted from Gorely volcano since the Pleistocene. Fractional crystallization dominated evolution of the Old Gorely magmas, whereas magma mixing is more prominent in the Young Gorely eruptive products. The role of rechargeevacuation processes in Gorely magma evolution is negligible (a closed magmatic system); however, crustal rock assimilation plays a significant role for the evolved magmas. Most Gorely magmas differentiate in a shallow magmatic system at pressures up to 300 MPa, ∼3 wt% H2O, and oxygen fugacity of ∼QFM + 1.5 log units. Magma temperatures of 1123–1218 °C were measured using aluminum distribution between olivine and spinel in Old and Young Gorely basalts. The crystallization sequence of major minerals for Old Gorely was as follows: olivine and spinel (Ol + Sp) for mafic compositions (more than 5 wt% of MgO); clinopyroxene and plagioclase crystallized at ∼5 wt% of MgO (Ol +Cpx + Plag) and magnetite at ∼3.5 wt% of MgO (Ol + Cpx + Plag +Mt). We show that the shallow magma chamber evolution of Old Gorely occurs under conditions of decompression and degassing. We find that the caldera-forming eruption(s) modified the magma plumbing geometry. This led to a change in the dominant magma evolution process from fractional crystallization to magma mixing. We further suggest that disruption of the magma chamber and accompanying change in differentiation process have the potential to transform a shield volcanic system to that of composite cone on a global scale.
Item Type: Article
Title: Abrupt transition from fractional crystallization to magma mixing at Gorely volcano (Kamchatka) after caldera collapse
Language: English
Journal or Publication Title: Bulletin of Volcanology
ISSN Print: 0258-8900
Subjects: State scientific and technical information rubricator (ГРНТИ) > 38 ГЕОЛОГИЯ > 38.37 Петрография > 38.37.25 Вулканология
Volcanoes > 1 Volcanoes of the Kurile-Kamchatka Region > 1.1 Kamchatka > Gorely
Depositing User: А.Ю. Озеров
Date Deposited: 11 Mar 2019 04:50
Last Modified: 11 Mar 2019 04:50
URI: http://repo.kscnet.ru/id/eprint/3545

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