Geological Study of Partial Melting of Mafic Rock-Bearing Heterogeneous Upper Mantle

点击翻译按钮获取中文摘要

This research investigated the partial melting and mantle-melt reaction occurred in the Horoman peridotite on the basis of field occurrence and major and trace element abudances in mafic rocks. As a result of study, Type I mafic granulite of the Horoman peridotite were experienced remelting event about 80 million years ago. The center of the mafic layer may have been garnet clinopyroxenite while the margin was a primitive melt in equilibrium with the center in terms of trace elements. Both are now metamorphosed into mafic granulite during uplifting of the Horoman peridotite.Following this study, I investigated the mantle section of the Oman ophiolite in 2004-2005 to understand formation of chemical heterogeneity by partial melting of oceanic upper mantle. Detailed analysis of mineral compositions of peridotite samples revealed the presence of highly refractory peridotite zone that obliquely crosscuts the mantle section parallel to the low temperature shear zone. It is advocated that the refractory zone formed by remelting of harzburgite due to reduction of solidus temperature as a result of fluid flow along shear zone.Third, heterogeneity of oceanic upper mantle was directly examined using peridotite samples drilled at Mid-Atlantic Ridge in 14°N〜16°N during ODP Leg 209. Optical investigation under microscope and analysis of mineral compositions for drilled cores from Hole B, Site 1271showed that melt flow and mantle-melt reaction in shallowest upper mantle produced a series of lithologies such as impregnated dunite, olivine gabbro, gabbronorite and troctolite as hybrid rocks between dunite and mafic melt.