Fluxes of volatiles from volcanoes of Kamchatka

• Main Authors: Plechova, Anastasiya, Portnyagin, Maxim, Mironov, Nikita
• Format: Conference Object
• Language: unknown
• Published: 2011
• Subjects: Kamchatka
• Online Access: https://oceanrep.geomar.de/id/eprint/11990/

Evaluation of short and long-term effects of volcanism on the global climate requires quantitative estimates of the volcanic emission of volatiles. One cannot directly measure the amount of volatiles emitted by volcanoes in the past but can estimate it using petrologic methods based on study of melt inclusions. In this work we estimate emission of volatiles resulted from basaltic volcanism in Kamchatka since the last Ice Age using data on volatiles in olivine-hosted melt inclusions. We studied about 900 glassy and experimentally homogenized olivine-hosted (Fo92-65) melt inclusions from 10 volcanic centers representative for 3 volcanic zones of the Eastern Volcanic Belt of Kamchatka: volcanic front (Ksudach, Zheltovsky, Vysoky, Krasheninnikov, Karymsky and Zhupanovsky volcanoes), rear-arc (Zavaritsky volcano and Tolmachev Dol) and the southern segment of the Central Kamchatka Depression (SCKD) (Klyuchevskoy volcano and Tolbachinskiy Dol). The compositions of rocks studied range from low- to high-K basalts and basaltic andesites and are representative for major magma types of the Eastern Volcanic Belt. Inclusions were analyzed for volatiles (S, Cl, H2O, F), major and trace elements using electron and ion microprobes. H2O content in the most primitive inclusions is 2-3.5 wt% for EVF, 2.5-3.5 wt% for SCKD volcanoes and ~1.5 wt% for rear-arc Zavaritsky volcano. This difference in water content between frontal and rear-arc EVF volcanoes can be explained by decreasing water concentrations in parental melts and their sources with increasing depth from volcano to the subducting plate (Portnyagin et al. 2007). H2O concentrations in EVF melts decrease with increasing K2O and indicate degassing of water during crystallization. The rate of water degassing is much slower than that of sulfur. No more than ~ 50% of the initial water content is lost from magmas at 70% of crystallization. H2O content in SCKD melts increases up to 5-5.5 wt.% during first 30-35 % of fractionation (Fo82-83) and then decreases due to degassing at ...