Magma storage and mingling conditions for the 2006–2010 eruptions of Bezymianny Volcano (Kamchatka): insights from mafic enclavesтезисы доклада

Дата последнего поиска статьи во внешних источниках: 6 февраля 2020 г.

Работа с тезисами доклада


[1] Davydova V. O., Shcherbakov V. D., Plechov P. Y. Magma storage and mingling conditions for the 2006–2010 eruptions of bezymianny volcano (kamchatka): insights from mafic enclaves // Abstract. IAVCEI Scientific Assembly Forcasting Volcanic Activity'. — Portland, США, 2017. — P. 245–245. The 2006-2012 eruption products of the Bezymianny volcano (Kamchatka) are represented by two-pyroxene andesites with 56.5 to 57.5 wt. % SiO2. Andesites contain evidence for magma mingling, caused to the intrusion of different magma in andesitic magma chamber. Such petrological evidence are plagioclases and pyroxenes with complex reverse zoning and dissolution surfaces; non-equilibrium xenocrysts (relicts of Hbl and Ol); different enclaves, which show signs of molten state at time of interaction with andesite. This study devoted to mafic enclaves (50 to 57.5 wt. % SiO2). We subdivide their into four distinct types (A-D) with different morphological, textural, chemical and petrological features. Type A-C interpreted as products of predominant crystallization parental magma during ascent and after injection to the shallow andesitic magma chamber. Differences between them correspond to different crystallization rate and different andesitic contamination degree. Type D interpreted as products of early crystallization at depth. All enclaves have non-equilibrium phenocryst assemblages, which correspond to crystallization at different levels of magma plumbing system. We subdivide three major mineral paragenesis: • “shallow chamber paragenesis” – Pl-Opx-Cpx-Ti-Mt (T: 940-980oC, P ∼ 1 kbar) • “deep paragenesis” – Hbl-Pl±Px (T: 960-1040oС, P: 5-9 kbar) • “mantle paragenesis” – xenocrysts of Ol with Cr-Spl or detritus of spinel harzburgites This paragenesis meet two-chamber magma plumbing system, which was proposed by result of geophysical and geochemical studies, and allow to specify the P-T conditions of magma interaction. Shallow magma chamber (andesitic, T ∼ 940-980⁰C и P ∼ 1 kbar) periodically provide by more water and mafic magma, which comes from deem magma chamber (andesibasaltic, T: 960-1040oС, P: 5-9 kbar). In deep magma chamber forming Hbl-Pl cumulates (type D enclaves). Injection of mantle-derived magma into deep chamber leads to heat up 1050-1090⁰C and partial melting of cumulates. Injection of mantle-derived magma and partial melting of cumulates resulted in the displacement of andesibasaltic magma into shallow chamber. In turn, this injection resulted to heat andesitic magma up 1000-1020⁰C and initialization of eruption.

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