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- Title
Low Crustal Fluid Reservoirs in Ultramafic Cumulates of Kamchatka.
- Authors
Simakin, A. G.; Shaposhikova, O. Yu.
- Abstract
Based on published geophysical and petrological data, lower crustal fluid reservoirs have been proposed below the Klyuchevskoy Volcano, expressed as a low Vp/Vs anomaly. A high Vp/Vs anomaly under the proposed fluid reservoir is interpreted as a zone of magma accumulation. The localization of fluids in these reservoirs in the ductile lower crust can vary from isolated inclusions to filling of microfractures over a time scale of several months. Using a simplified poroelastic model, it is shown that the transition in the topology of pore space filled with fluid or melt can provide the observed changes in Vp/Vs in the anomalies of high and low values at a melt content of several vol % and fluid content less than 1 vol %, respectively. In zones of active volcanism, such as the Klyuchevskaya group of volcanoes (KGV), fluid reservoirs are localized in ultramafic cumulates formed during the early high-temperature stage of magma fractionation. Ultramafic xenoliths in the products of eruptions of the KGV and Avachinsky volcanoes, often interpreted as mantle rocks, formed at pressures of about 5 kbar or depths of about 18–20 km in accordance with two-pyroxene geo-thermobarometry and the content of volatiles in melt inclusions in olivine and spinel. When crossing by ascending magmas, the fluid-containing reservoir experiences mechanical failure and injects a certain amount of fluid into the magma, which then captures pieces of crushed magmatic cumulates. The composition of melt inclusions in olivine can reveal records of the magma-fluid interaction.
- Subjects
REGOLITH; MECHANICAL failures; FLUIDS; INCLUSIONS (Mineralogy &; petrology); POROELASTICITY; VOLCANIC eruptions; INCLUSIONS in igneous rocks
- Publication
Petrology, 2023, Vol 31, Issue 6, p705
- ISSN
0869-5911
- Publication type
Article
- DOI
10.1134/S0869591123060036