GRANITOIDS AND TETONIC EVOLUTION OF THE WEST KUNLUN OROGENIC BELT

摘要

The West Kunlun orogenic belt, one of the least studied areas in China, is located at the junction between the Qinghai—Tibetan Plateau and Tarim Basin and has undergone intense tectonic action and frequent magmatism.The West Kunlun orogenic belt can be divided into five tectonic|magmatic evolution stages according to the character of the igneous rocks, metamorphic rocks, sedimentation mode, tectonic phases and isotopic ages(Fig 1).Active stages have dominated with only short intervening stable stages. This kind of evolution is not simply repeated but that a later stage is elevation and development of its former stage.Space|time distribution of granitoids varies with each different tectonic| magmatic stage as well as within different periods of the same tectonic| magmatism stage. Take time into condition , It is an important turning movement of tectonics|magmatism evolution during the Indo|Sinian movement, as space the middle fault (Jiang Chunfa 1982) of the West Kunlun orogenic belt is a significant border o f tectonics|magmatism evolution. Granitoids formed before Indo|Sinian movement are mainly distributed to the north of the middle fault of West Kunlun. These granitoids are mostly granites of early and middle Proterozoic, Caledonian and Hercynian ages. A unique control on the granitoid evolution is that they become younger from NE to SW, crossing the regional structure line. Granitoids formed after Indo|Sinian movement are mainly distributed to the south of the middle fault. But distribution of granitoids of early Yanshan cycle cut across the middle fault of West Kunlun Mountain. Their age distribution shows a bidirectional control with the granitoids becoming younger across the regional structural lines from NE and SW boundary fault to the interior of the fracture belts.