Materials of the International Conference
50th Anniversary of the International Geophysical Year
and Electronic Geophysical Year

16-19 September 2007 • Suzdal, Russia

Spatial distribution and degassing of the volatile elements (S, Cl and F) in magmas across the Kamchatka arc

T. G. Churikova

Institute of Volcanic Geology and Geochemistry, Far Eastern Branch RAS, Petropavlovsk-Kamchatsky, Russia

Abstract

The aerosol layer has an important role in the Earth's climate and the ozone layer formationarroll. There is a strong suggestion that the aerosol layer is fundamentally volcanic in nature. The research on volatiles in basaltic melts could supply such information for the Kamchatka region, which is one of the most active volcanic areas of the Northern Hemisphere and produced many large Plinian eruptions during Holocene with 29 presently active volcanoes. Due to high elevation of the volcanoes (e.g. Kluchevskoy volcano, 4750 m) many of the eruptions reach the stratosphere and may thus result in significant input of volatiles to the upper atmosphere. Because the volatile elements in whole rocks are strongly affected by degassing before and during eruption, melt inclusions trapped in pristine igneous minerals are potentially the best data source to study initial volatile contents in primary and parental melts. Therefore the homogenized melt inclusions in olivines were analyzed by electron microprobe and by SIMS to study the regional distribution of volatiles (S, Cl and F) and some trace elements across the Kamchatka arc. The sample collection represent a traverse covering the Eastern Volcanic Front (EVF), the Central Kamchatka Depression (CKD), and the Sredinniy Ridge (SR) of back arc. Sulfur concentrations in the melt inclusions increase slightly from EVF to CKD but significantly decrease in the SR lavas. The chlorine concentrations in melt inclusions from EVF and CKD are similar and also decrease in SR melts. In contrast, the EVF and CKD melt inclusions are depleted in fluorine, while the SR samples are twice enriched. The magmatic degassing is the process responsible for volatiles emission out of magma. The research on volatiles show that sulfur is strongly affected by degassing before and during eruption. Chlorine degasses with less extend compared to sulfur. Fluorine is not affected by degassing in any of the melts measured and stay in the melt. Enrichment of CKD melts in S coupled with highest U/Th, 87Sr/86Sr, 18O, 11B and chalcophile elements results from a high fluid flux from the altered subducted oceanic crust and subducted Emperor Seamount chain. The strongest slab signature is associated with the highest magma production rate in this region. These data suggest that continuous, volumetric and high-altitude eruptions of Kluchevskaya Group of volcanoes could supply significant amounts of sulfur and chlorine to the stratosphere and probably could influence climate in the Northern Hemisphere.

Citation: T. G. Churikova (2007), Spatial distribution and degassing of the volatile elements (S, Cl and F) in magmas across the Kamchatka arc, in: Materials of the International Conference '50th Anniversary of the International Geophysical Year and Electronic Geophysical Year', GC RAS, Moscow, doi:10.2205/2007-IGY50conf.

© 2007 Geophysical Center RAS and authors


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