南黄海千里岩岛榴辉岩的矿物化学及成因探讨

南黄海千里岩岛地处中国华南板块与华北板块缝合线位置,其基底由强烈韧性变形的构造片麻岩组成,并出露具重要大地构造标型意义的超高压榴辉岩类岩石。本文通过对南黄海千里岩岛榴辉岩中主要造岩矿物石榴石的矿物化学研究,探讨了榴辉岩的成因。研究表明,千里岩地区高压变质岩是由于华北与华南两大陆块拼合时,处于其间的岛弧拉斑玄武岩沿碰撞带下插到华北陆块之下,从而使千里岩地区发生高压变质作用,形成了榴辉岩和片麻岩等,后期的构造折返使其上升到地壳上部。

A STUDY ON THE MINERALCHEMISTGRY AND GENESIS OF THE ECLOGITE FROM QIANLIYAN ISLAND,THE SOUTHERN HUANGHAI SEA

Qianliyan Island,the southern Huanghai Sea is located in the suture zone of South China and North China plates.The basement of Qianliyan Island consisits of intensely ductile deformationed tectonic gneiss.UHP eclogite,which has important tectonic implication,is exposed in this area.Studying the genesis of the eclogite by investigating the mineralchemistry of the garnet,major rock-forming minerals in the eclogite,it is found that HP metamorphic rocks from Qianliyan Island were formed in the undermentioned process.When the North China plate collided with the South China plate,the tholeiite between the two plates dived along the collision zone to the underside of the North China plate and high pressure metamorphism occurred in the Qianliyan area which engendered eclogite and gneiss,which rose to the upside of the crust as a result of later exhumation.