蛇绿岩中的花岗质岩石成因类型与构造意义

ROCK TYPES AND TECTONIC SIGNIFICANCE OF THE GRANITOIDS ROCKS WITHIN OPHIOLITES

花岗质岩石在蛇绿岩的岩石组合中只占很小部分 (通常 <10 % ) ,但是对于蛇绿岩的成因研究 ,特别是对蛇绿岩形成和演化过程的精确年龄测定 ,具有重要的意义。简要回顾了蛇绿岩中花岗质岩石的研究历史。近年来的研究表明 ,蛇绿岩中的花岗质岩石不仅包括直接由大洋玄武质岩浆结晶分异形成的花岗质岩石 ,即传统意义上的大洋斜长花岗岩 ,还包括蛇绿岩在形成、演化过程中本身形成的和侵入的花岗质岩石。根据成因 ,可以将这些花岗质岩石分为 4类 :结晶分异型花岗岩、剪切型花岗岩、俯冲型花岗岩和仰冲型花岗岩。

The minor granitoids (general <10%) in the ophiolite are important for studying origin of the ophiolite, especially dating the precise ages of the ophiolites formation and evolution. It is simple review research history of the granitoids within the ophiolites in this paper. The recent research shows that granitoids rocks within the ophiolites include not only the granites formed by fractionation of MORB at low pressure, but also the granites which formed by partial melting of gabbros of ophiolites in shear zone or intruded it during the formation and evolution of the ophiolite. Based on the origin of the granitoids, they are subdivided into four types: fractionation-type;shearing-type;subduction-type, and obduction-type. The geochemical characteristics, tectonic setting and geological implication of the granitoids are systemically summarized in this paper. Discrimination and timing the different type granitoids within the ophiolites would precise constrained the times of the ophiolite evolution from spreading of ocean crust, subducting of ocean crust and obducting onto the continental crust. It is important for understanding the origin and evolution of the ophiolites.