Origin of Asymmetric Symplectitic Texture in Mantle Xenoliths from the Fangshan Basalt, Eastern China

Mantle-derived xenoliths brought to the Earth’s Surface by basalts are important windows to understand composition, evolution and processes of the lithospheric mantle. The lithosphere of the southeastern China is dominated by peridotite or lherzolite [1, 2]. The spinel peridotite xenoliths studied are from Fangshan basalt, eastern China, which are composed of olivine, clinopyroxene, orthopyroxene and spinel with some interstitial phases (Fig. 1). Previous studies of the mantle xenoliths indicated that the lithospheric mantle has undergone partial melting and metasomatism [1]. A significant feature of these mantle xenoliths is that they often have asymmetric symplectitic textures along rims of minerals such as clinopyroxene [3] and spinel (Fig. 2). Symplectite is a textural term that generally refers to 1) intergrowth of minerals along the rims of other minerals, 2) a breakdown product of primary phases such as garnet, pyroxene or spinel, or 3) reaction products between minerals and fluids/melts [4, 5, 6].