Compositional Peculiarities and Genesis of Melt Inclusions in Plagioclase from the Apakhonchich Lava Flow, Klyuchevskoi Volcano, Kamchatka

摘要

Melt inclusions in plagioclase of the Apakhonchich basalt flow of Klyuchevskoi volcano point to the existence of two types of melts: more basic (65-66 wt % SiO_2), which seem to have corresponded to a late stage in the basalt melt evolution, and more acid (69-76 wt % SiO_2), which were produced by the partial melting of the magma feeder walls during magma ascent. A comarison with data on other volcanoes indicates that this mechanism is typical of island-arc volcanic series. Experimental data on equilibria between melt and plagioclase were used to develop a technique for a qualitative assessment of water contents in metls. According to such data, the melts in question remained water-saturated throughout the whole time period of plagioclase crystallization.