华中榴辉岩域的岩浆型榴辉岩及其形成机制

MAGMATIC ECLOGITE AND ITS FORMATION MECHANISM OF THE ECLOGITE DOMAIN IN CENTRAL CHINA

中国中部鄂豫皖苏鲁的榴辉岩分布面积约达50000km^2,构成地球上一个罕见的宏大的榴辉岩域。榴辉岩的主体围岩是长英质片麻岩,它与榴辉岩不是相同高压变质作用的产物。据榴辉岩和超基性-基性岩的密切共生关系及榴辉岩与其它岩石之间的产出特征、结构构造和岩石地球化学特征等,认为榴辉岩是一种深成的基性岩浆岩。长英质片麻岩的原岩是花岗岩类。在华北与扬子两个板块碰撞过程中,使先期形成于上地幔或壳幔之间的榴辉岩等暗色岩系破碎,并被板块碰撞引发形成的花岗质岩浆裹携,上升侵位于前古生界和部分古生界岩石中,以后又遭受多次构造-岩浆热事件的改造而呈现如今复杂的面貌。

Eclogite that spreads over an area of some 50000 km2 in Hubei, Anhui, Jiangsu and Shandong Provinces of central China, comprises a rare, gigantic eclogite domain on the earth. Felsic gneiss is the preddmonant country rock around the eclogites. Both the eclogite and the felsic gneiss have not undergone the same high-pressure metamorphic event. On the basis of the intimate association between eclogite and ultrabasic-basic rocks and the occurrence, structures and textures and alteration of minerals and geochemical features of eclogites and relevant rocks, the e-clogite is postulated to be originally a basic plutonic rock, and the source rock for the felsic gneiss to be intermediate to acid granitoids. During the collision process of the North China and Yangtze plates, the preexisting eclogite and melanoeratic rock series formed in the upper mantle or between the mantle and crust were broken and trapped in the granitic magma produced by the collision; then the granitoids with melanoeratic rocks were uplifted and emplaced in the pre-Palaeo-zoic and partly Palaeozoic rocks. Later they were together modified by multiple of tectono-mag-matic thermal events in the Phanerozoic and finally assume the present complex appearence.