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Garnet-pyroxenite-derived end-member magma type in Kamchatka: evidence from composition of olivine and olivine-hosted melt inclusions in Holocene rocks of Kekuknaisky Volcano

Nekrylov, NA, Popov, DV, Plechov, PY, Shcherbakov, VD, Danyushevsky, LV ORCID: 0000-0003-4050-6850 and Dirksen, OV 2018 , 'Garnet-pyroxenite-derived end-member magma type in Kamchatka: evidence from composition of olivine and olivine-hosted melt inclusions in Holocene rocks of Kekuknaisky Volcano' , Petrology, vol. 26, no. 4 , pp. 329-350 , doi: 10.1134/S0869591118040057.

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Abstract

Late Quaternary volcanoes of Sredinny Range (Kamchatka) attract geoscientists’ attention by their unusual geochemical features and geodynamic setting. They produced volcanic rocks that are enriched relative to N-MORB in most of incompatible trace elements (except HREE), including strong enrichment in large-ion lithophile elements, and show a negative Nb–Ta anomaly, which is typical for rocks formed in supra-subduction settings. However, modern subduction of the Pacific Plate does not reach the most part of Sredinny Range, as inferred by mapping of Wadati–Benioff zone or seismic tomography. We constrain the source of parental magmas for Sredinny Range volcanic rocks by combining major and trace element geochemical data for olivine and naturally quenched olivine-hosed melt inclusions for Holocene tephra layers of the Kekuknaisky field. Composition of the most magnesian olivine (Ni > 2000 ppm, Fe/Mn ≈ 75 at Mg# ~ 84–85 mol %) and geochemical characteristics of the most primitive melts (FC3MS = 0.61 ± 0.04 (2σ)) are consistent with their derivation from a pyroxenite source, while elevated LREE/HREE ratios in lavas indicate that it contained garnet. This garnet-bearing pyroxenite likely originated from the lower crust or lithospheric mantle. Its melting could have occurred due to delamination and sinking into the hotter mantle.

Item Type: Article
Authors/Creators:Nekrylov, NA and Popov, DV and Plechov, PY and Shcherbakov, VD and Danyushevsky, LV and Dirksen, OV
Keywords: olivine, melt inclusions, pyroxenite, source, Kamchatka
Journal or Publication Title: Petrology
Publisher: Interperiodica
ISSN: 0869-5911
DOI / ID Number: 10.1134/S0869591118040057
Copyright Information:

Copyright 2018 Pleiades Publishing, Ltd.

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