塔里木古大陆东缘的微大陆块体群

Microcontinents on the eastern margin of Tarim paleocontinent

塔里木古大陆东缘至少存在 4个微大陆 ,自北而南分别是阿拉善、祁连、欧龙布鲁克和柴达木微大陆 ,它们有相近但又有一定差异的早前寒武纪变质基底和中元古代变质沉积地层。每一个微大陆边缘均有复杂的生成历史 ,特别是新元古代早期的热 -构造事件十分发育 ,并在柴达木微大陆北缘形成一条长 70 0km的花岗片麻岩带 ,而在多数微大陆边缘则叠加了寒武纪至奥陶纪火山弧或蛇绿混杂岩。在微大陆之间自北而南分别发育了北祁连蛇绿岩混杂岩带、南祁连蛇绿岩混杂岩带、沙柳河 -鱼卡河高压 -超高压变质带和昆仑中部清水泉蛇绿混杂岩 ,它们代表了微大陆之间的结合带 ,其形成时代集中在寒武纪至奥陶纪。这几个微大陆总体表现出亲塔里木古大陆的特征 ,特别是自新元古代以来具有相似的地质演化特征。

There were at least four microcontinents on the eastern margin of the Tarim paleocontinent prior to Early Paleozoic. They are, from north to south, Longshoushan, Qilian, Oulongbuluke and Qaidam, which have somewhat similar yet different Early Precambrian metamorphosed basements and Mesoproterozoic meta_sediments. Quite complex geological evolution was detected along the margins of these microcontinents, especially along the margin of Qaidam, where a Neoproterozoic granite gneiss belt over 700 km long is developed. In addition, Cambrian and Ordovician volcanic arc and ophiolite melange were superimposed upon the microcontinental margins. From north to south, the north Qilian ophiolite melange,the south Qilian ophiolite melange, the Shaliuhe_Yuqiahe high_pressure and super high_pressure meta_morphic belt and the Qingshuiquan ophiolite melange in central Kunlun Mountains are developed between two adjacent microcontinents, representing suture belts between two microcontinents. The suture belts are from Cambrian to Ordovician in age. Geological characteristics of these microcontinents, especially the characteristics since Neoproterozoic, are generally similar to features of the Tarim paleocontinent. However, the time and location of amalgamation between the Tarim and the microcontinents require further investigation.