辽宁西丰一带侵入岩形成环境和成因探讨

DISCUSSION ON THE FORMING ENVIRONMENT AND ORIGIN OF THE INTRUSIVE ROCKS IN XIFENG AREA, LIAONING PROVINCE

西丰一带侵入岩即以前所说的西丰大岩体,是布列亚-张广才岭巨型花岗岩带组成部分.该巨型花岗岩带记录了造山带从古亚洲洋板块开始俯冲、洋盆闭合到增生造山演化过程的基本信息.现在已经将规模宏大的西丰大岩体进行了详细解体,重新归并成4个侵入期次,划分为11个侵入序次,统称辽宁省西丰一带侵入岩.在详细解体、重新归并和划分的基础上,进一步探讨了各序次侵入岩形成的温压条件、构造环境、物质来源与成因.早二叠世第一序次、第二序次侵入岩以及中侏罗世第一序次侵入岩为I型花岗岩,晚白垩世第三序次(闪长玢岩)也为I型,主要物质来源是地壳中岩浆岩重熔的成分.其余各序次侵入岩均为S型花岗岩,主要物质来源是地壳中沉积岩重熔的成分.西丰一带,早二叠世第一个序次侵入岩为火山弧型深成岩,早二叠世第二个序次侵入岩为火山弧型与同碰撞型的过渡类型.早二叠世第三序次至中侏罗世第各序次侵入岩和晚白垩世各序次侵入岩为同碰撞型和碰撞后型花岗岩.这些特征与古亚洲洋晚期的消减、闭合和增生造山演化序列基本吻合.

The intrusive rocks in Xifeng area, Liaoning Province, formerly called Xifeng intrusive body, are component parts of the Bureya-Zhangguangcailing giant granite belt, which recorded the essential information of evolution process of the orogenic belt from the Paleo-Asian oceanic plate subduction, through ocean basin closure to accretion orogeny. Presently,the Xifeng intrusive body has been disintegrated and reassigned into four intrusion stages, including 11 intrusion orders, and referred to as the intrusive rocks in Xifeng area. On the basis of the new division, forming temperature-pressure condition,tectonic environment, material sources and origin of the rocks are further discussed. The intrusive rocks of the first-and second-order of Early Permian and the first-order of Middle Jurassic Epoch belong to I-type granite. The intrusive rocks（diorite porphyry） of the third-order of Late Cretaceous are also I-type. Their material source is mainly from the remelting of magmatic rocks in the crust. The intrusive rocks of the other orders are S-type granite, with main material source from the remelting of sedimentary rocks in the crust. The intrusive rocks of the first-order of Early Permian are plutonic rocks of the volcanic arc; while those of the second-order are the transition type between volcanic arc and syn-collisional. The intrusive rocks after that are syn-collision or post-collision type granites. These characteristics are basically consistent with the evolution sequence of subduction, closure and accretion orogeny of the Paleo-Asian ocean plate.