HYDROCARBONS IN MAGMATIC FLUID IN PHENOCRYSTS OF ERUPTION PRODUCTS OF THE MEN'SHII BRAT VOLCANO (Iturup Island): DATA FROM PYROLYSIS-FREE GAS CHROMATOGRAPHY-MASS SPECTROMETRY OF MELT AND FLUID INCLUSIONS
I.R. Nizametdinov1,2, D.V. Kuzmin1,2, S.Z. Smirnov2, T.A. Bul'bak2, A.A. Tomilenko2, I.A. Maksimovich2, A.A. Kotov3
1Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Tohoku University, Aza-Aoba 6-6-20, Aramaki, Aoba, Sendai 980-8579, Japan
Keywords: Hydrocarbons, fluid and melt inclusions, basalts, rhyolites, volatile components, Kuril Island arc, Iturup Island
Abstract
Pyrolysis-free gas chromatography-mass spectrometry was used to determine the gas phase composition of inclusions in phenocrysts from basalts and rhyolites of the Men’shii Brat Volcano (Medvezh’ya caldera, Iturup Island). Among more than 300 compounds detected in the inclusions, hydrocarbons are predominant (52-92 rel.%). These hydrocarbons (С1-С17) are alkanes, alkenes, alcohols, polycyclic aromatic hydrocarbons, ethers and esters, aldehydes, ketones, and carboxylic acids as well as sulfonated, nitrogenated, and halogenated organic compounds. Inorganic substances, which are predominantly CO2, H2O, SO2, and N2, are present in subordinate amounts. The organic compounds are interpreted as products of abiogenic synthesis of hydrocarbons in magmatic gases. This fundamentally new information about the composition of magmatic fluid suggests that mantle and crustal magmas can transport hydrocarbon substance.
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