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洋中脊玄武岩(MORB)覆盖了约60％的地球表面。在大洋中脊喷出的这种次碱性玄武岩(拉斑玄武质)岩浆的庞大体积和上地幔中这些岩浆的生成都表明,洋中脊火山作用是地幔化学分异作用中最主要的事件之一。洋中脊环境产生的玄武岩不受大陆壳物质的污染。因而它们可能记录了下伏地幔的化学特征。因此,MORB的成因研究成了玄武岩岩石学的一个主要课题。对于了解洋中脊系统轴部层状洋壳的产生过程,这也是一个具有深远意义的课题。
Mid-ocean ridge basalts (MORB) cover about 60% of the earth’s surface. The massive volume of this subbasal basalt (tholeiite basaltic) magma ejected from mid-oceanic ridges and the formation of these magmas in the upper mantle all indicate that mid-ocean ridge volcanism is the most important event in mantle chemical differentiation one. Basalts produced in mid-ocean ridges are not contaminated by continental shell matter. They may therefore document the chemical features of the underlying mantle. Therefore, the genesis study of MORB has become a major topic of basaltic petrology. It is also a far-reaching topic for understanding the production process of stratiform oceanic crust in the mid-ocean ridge system.