上部マントルの部分溶融とマグマの上昇 : 超塩基性岩の研究より

概要

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Two examples of mantle-derived alpine-type peridotites, one from Ronda, Spain and the other from Horoman, Japan are reviewed in the context of magma generation and migration in the upper mantle. The peridotite bodies are characterized by layered structure of variable scales and by the presence of mafic layers intercalated within the peridotite. Detailed investigations of the Horoman body revealed that the layering is wavy and oscillatory across the layer structure in terms of chemical and mineralogical composition. A new hypothesis recently proposed for the melt segregation processes is reviewed, in which the layering and the chemical variation of the peridotite are best explained in terms of the partial melting and melt segregation in an ascending partially molten mantle. Because permeable flow of partial melt is coupled with the compaction of the solid in a deformable matrix, magma waves may be generated in the gravity field due to the nonlinear effect of the flow. The layering observed in many alpine-type peridotites may be the "fossils" of such magma waves.
特定非営利活動法人日本火山学会の論文
1986-04-30