海洋コアコンプレックスから得られたかんらん岩の重要性：中央海嶺下マントル物質の不均質性とメルトの存在

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Abyssal peridotite is widely accepted as residual mantle material after partial melting and melt extracted beneath mid-ocean ridge, and is contributed to understanding of magmatism forming oceanic lithosphere. Peridotite samples from the oceanic core complex of the ridge-transform intersection corner high recently provide new insight of upper mantle material inhomogeneity in terms of degree of melting and further melt-related processes. Compiling data of Cr# [Cr/(Cr+Al) atomic ratio] of spinel and clinopyroxene REE compositions of abyssal peridotite from the slow- and ultraslow-spreading mid-ocean ridges, accumulated since 1980s, demonstrate that depleted peridotites are dominantly collected from the oceanic core complex and abyssal plane at shallower depth (<2500 m below sea level), contrasting to relatively fertile peridotite from the transform wall at deeper part of the fracture zone. Various enrichment of clinopyroxene REE compositions in such depleted peridotite reflects that the melt is involved in or after the partial melting stage. The compiling data suggest that the compositional variation of abyssal peridotite is dependent on the mid-ocean ridge structure and that the inhomogeneity of upper mantle material is recognized in regional scale, contrasting to the global-scale inhomogeneity already discussed in previous abyssal peridotite studies. Drilled core peridotite samples from the Atlantis Massif, Mid-Atlantic Ridge 30°N are good example to reveal that the melt penetration into residual peridotite is an important role for creating inhomogeneity of rock-sample scale on the oceanic core complex formation.
日本鉱物科学会の論文

海洋コアコンプレックスから得られたかんらん岩の重要性：中央海嶺下マントル物質の不均質性とメルトの存在

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