Abstract
In the eastern margin part of Asia, there are two old subduction zones striking ranged north to south are recognized. They were also accompanied with accretionary prisms that are dated the Jurassic - Early Cretaceous and the Early Cretaceous - Late Cretaceous. These accretionary prisms were composed of ophiolite and greenstone, which were intruded ultra-mafic volcanic dyke and alkali basalt and picritic basalt. Within these volcanic rocks, mafic volcanics are containing of high MgO (> 18.0 percent) is named as meimechite. Although their MgO content is higher than those of the picritic basalts, meimechite contains less total alkalic component than those of typical alkaline rocks. In the major element compositions, meimechites are similar to komatiites. To resolve the magma source of meimechite is important on geochemical evolution of deep Earth interior, because the secular source variation of komatiite magma is inferred to date, which is implied their deep origin. In this study, we obtained the some preliminary data of Cretaceous - Neogene ultramafic rock sampled from the Mineoka, Setogawa and Sikhote Alin area.
