かんらん岩からマグマ生成メカニズムをさぐる : 固相を主体とする開放的マグマ系

概要

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A general mass balance equation for open magma system is formulated to be appropriate for extraction of magmatic information from mantle peridotites. The equation is applied to understand the origin of petrologic mantle arrays; olivine-spinel mantle array (Arai, 1987) and mantle olivine array (Takahashi, 1986). For the olivine-spinel mantle array, batch melting model and fractional melting models are examined. The array can be reproduced by a batch melting (or fractional melting) by using plausible set of model parameters that are consistent with results of melting experiments. The batch melting trend is not significantly different from that of fractional melting at least before clinopyroxene is completely consumed. For this mantle array, various stoichiometric coefficients for the melting reaction and the initial bulk composition of a fertile peridotite were tested to give constraint on those parameters. The Mg-rich part of the mantle olivine array can also be reproduced by either batch or fractional melting, but its Fe-rich segment may be most plausibly derived from a reaction between Mg-rich olivine on the manyle array and melt in equilibrium with less magnesian and NiO-poor olivine. The reaction process can be either batch, open-system, or percolation reactions.
特定非営利活動法人日本火山学会の論文
1997-04-25