HR: 0800h
AN: V41A-1424    [Abstracts]
TI: Volatile Content in Melt Inclusions in Variable &δ18O Olivines From Klyuchevskoy Volcano, Kamchatka, Russia.
AU: * Auer, S L
EM: sauer@uoregon.edu
AF: University of Oregon, Department of Geological Sciences 1272 University of Oregon, Eugene, OR 97405
AU: Bindeman, I
EM: bindeman@uoregon.edu
AF: University of Oregon, Department of Geological Sciences 1272 University of Oregon, Eugene, OR 97405
AU: Ponomareva, V
EM: bazli@kcs.iks.ru
AF: Institute of Volcanology & Seismology, PIIP Blvd. 6 , Petropavlovsk, 683006 Russian Federation
AU: Wallace, P
EM: pwallace@uoregon.edu
AF: University of Oregon, Department of Geological Sciences 1272 University of Oregon, Eugene, OR 97405
AB: Klyuchevskoy group volcanos in the Central Kamchatka Depression have the highest magma production rates in the world. Among these, the 4750m high Klyuchevskoy volcano, only approximately 7000 years old, erupts every 5 to 10 years, with the latest summit eruption in March 2005. Magma compositions range from high-Al to high-Mg basalt and basaltic andesite with 5 to 11 wt% MgO. Mg-rich olivines are present throughout the different magma compositions, and range in Fo content from 92 to 75%. Klyuchevskoy basalts also exhibit the highest δ18O in the world with d18O olivine ranging from 5.6 to 7.2 ‰, including olivines of this study. To constrain the primary volatile concentrations of the parental magmas, we analyzed H2O in olivine-hosted melt inclusions from tephrochronologically-dated tephra layers on the flanks of the volcano. Analyzed samples include three tephra layers of high-Al composition and one high-Mg sample. Olivine from these tephra layers span 1.5 permil in d18O from high-d18O to normal-d18O values. The range in H2O contents of melt inclusions from each tephra layer are similar (0.9 to >4 wt% H2O) the latter numbers being higher than measured previously for Klyuchevskoy, but similar to maximum values found for some other arc basalts. In particular, even high-Mg basalts have high H2O concentration, which we believe reflects a primary magma signature. Melt inclusions with lower H20 contents were probably trapped from partially degassed melts at various depths during ascent and/or represent recycling of low pressure, variable Fo olivines that were syneruptively entrained in magma. We are correlating the measured volatile concentrations with Mg#, d18O, age, and metl inclusion composition, but the preliminary results suggest only subtle correlations. These are studied in an attempt to explain the origin of the uniquely high-d18O signature of Klyuchevskoy as being a primary signature of high-d18O subduction fluids vs. assimilation of water bearing, high-d18O crustal compositions. Additionally, the petrogenetic history of high-Al and high-Mg basalts seem to be intertwined in the sampled Klyuchevskoy tephrochronological record.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1043 Fluid and melt inclusion geochemistry
DE: 8430 Volcanic gases
DE: 8455 Tephrochronology (1145)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005