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

Abstract

—Pyrolysis-free gas chromatography–mass spectrometry was used to determine the gas phase composition of inclusions in phenocrysts from basalts and rhyolites of 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 (C1–C17) 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 on the composition of magmatic fluid suggests that mantle and crustal magmas can transport hydrocarbon substance.

Impact of Solid Hydrocarbon on the Composition of Fluid Phase at the Subduction (Experimental Simulation)

“…Thus, such compounds as alkanes, alkenes, arenes, phenols, aldehydes, carboxylic acids, esters, ketones, nitriles, PAH (polycyclic aromatic hydrocarbon), and their halogenated, methylated, and sulfonated derivatives were found in volcanic gases from Vulcano (Aeolian Islands, Italy), as well as various heterocyclic compounds including thiophenes and furans [26]. Hydrocarbon compounds, including high-molecular ones, and their oxygenated, nitrogenated, sulfonated, and halogenated derivatives were diagnosed by GC-MS in fluid inclusions in natural diamonds [27][28][29][30], in melt and fluid inclusions in phenocrysts from basalts and rhyolites from Men'shii Brat Volcano (Medvezh'ya caldera, Iturup Island) [31], and fluid inclusions in minerals from polymetallic sulfide deposits at Ashadze-1, Semenov-2, Krasnov, and Rainbow, and from the Lost City carbonate structures of hydrothermal fields in the Mid-Atlantic Ridge [32]. Stability of high molecular weight carbon compounds is also proved experimentally at high P-T parameters (at 5.3 Gpa and 1300 • C in the Fe-C-S system) [33].…”