Выпуск: 8 , Том: 58 , Год издания: 2017

Vitreous basalts and plagioclase lapilli from Tolbachik Volcano studied by high-temperature gas chromatography reveal features of a fluid regime uncommon to suprasubduction melts. Prominent depletion in volatiles confirms the anomalous behavior of the Tolbachik fluid systems. Vitreous basalts contain minor amounts of water (0.16-0.27 wt.%) and carbon dioxide (95-440 ppm). New data on volatiles in the Tolbachik plagioclase lapilli show very low contents of CO₂ and total gas (exclusive of H₂O) and enrichment in reduced fluids (CO and CH₄) relative to the basalts. In general, analysis of basalts and plagioclase lapilli from different eruptions trace a progressive increase in reduced fluids (CO and CH₄) and decrease in CO₂ and total gas from past to present events. The concentrations of CO₂ decrease, while those of CO and CH₄ in basalts and plagioclase lapilli increase systematically with an increase in FeO/MgO ratios and K₂O contents in the lavas and in anorthite component in plagioclase.