西准噶尔晚古生代残余洋盆消亡时间与构造背景研究

Study on extinction of the remnant oceanic basin and tectonic setting of West Junggar during Late Paleozoic

准噶尔西北缘克拉玛依蛇绿岩套及其上覆陆相火山-沉积岩系的研究表明,西准噶尔晚古生代残余洋盆是继承早古生代洋盆发生的,沉积作用基本连续,但同位素年代学研究表现出明显的早古生代和晚古生代两个阶段。残余洋盆的消亡是一个"软碰撞"过程,残余洋盆整体隆升消亡后,经历了329～320Ma、310～295Ma及290Ma三次构造-岩浆事件,爆发三期陆相火山喷发,形成巴塔玛依内山组、哈尔加吾组、卡拉岗组三个陆相火山-沉积岩系,准噶尔西北缘的佳木河组是跨越石炭-早二叠世包括多期火山-沉积作用的产物。晚古生代侵入岩经历了由小型浅成闪长岩、石英闪长岩、花岗闪长岩系列向大型深成富碱花岗岩系列的转化,可能是花岗闪长质过渡型地壳向花岗质成熟大陆壳转化的深部作用过程的反映。

The study on Keramay ophiolite suite and overlying continental volcanic-sediment rocks indicates that Late Paleozoic remnant oceanic basin in west Junggar formed after Early Paleozoic ocean. The deposition was nearly successive. However,the isotope chronology reveals two stages:Early Paleozoic and Late Paleozoic. The extinction of remnant oceanic basin was vie 'soft collision'. After rift and extinction of remnant oceanic basin,three tectonic-magma events developed in 329~320Ma,310~295Ma and ~290Ma,respectively,which induced continental volcanic eruptions at three periods,corresponding to the Batamayineishan Formation,Harjiawu Formation and Kalagang Formation,respectively. The Jiamuhe Formation consists of multiple volcanic eruptions from Carboniferous to Early Permian. Late Paleozoic intrusions have transform from small size diorite,quartzdiorite,granodiorite to hypogene large size alkali-rich granite,which may suggest the granodioritic transitional continental crust transformed to granitic mature continental crust.