滇西晚古生代以来的构造演化

滇西晚古生代以来的构造演化与特提斯演化密切相关。泥盆纪—石炭纪,伴随古特提斯洋开启,扬子大陆边缘发生裂解,兰坪—思茅地块、保山地块等相继形成独立地块,其间被哀牢山洋、昌宁—孟连洋分隔。晚二叠世,古特提斯洋关闭,滇西发生造山作用,其间在李仙江和澜沧江一带曾出现过火山岛弧。中三叠世,伴随中特提斯洋开启,地壳拉张裂陷,兰坪—思茅盆地开始形成。晚三叠世末—早侏罗世,中特提斯关闭,本区再次发生造山作用,造成下侏罗统缺失、从中侏罗世开始,由于新特提斯洋开启,地壳再次下沉接受沉积。喜马拉雅造山运动使新特提斯洋关闭,本区地壳大面积隆升,并在早期左行、晚期右行走滑断裂的影响下,形成一系列的走滑拉分盆地。晚古生代以来本区构造时开时合,整体显示手风琴式的演化特征。

Tectonic Evolution Since Late Palaeozoic Era in West Yunnan

Based on Palaeo-Tethys multi-island ocean framework,the tectonic evolution of the western Yunnan were begun since Late Palaeozoic Era. The margin of Yangtz continent was splitted following the formation of Palaeo-Tethys from D to C. Lanping-Simao mass and Baoshan mass were turned into independent blocks one after another because they were divided by Ailao Shan and Changning-Menglian subsidiary oceans. The orogenic deformations took place in western Yunnan and its adjacent region due to the closing of Palaeo -Tethys in Late P during which the volcanic arcs were formed along Lixian River and Lancang River. The Lanping-Simao basin began to be formed during T2 accompanying Mid-Tethys forming. The closing of Mid-Tethys made the orogenic deformations happen on more and J1 absence during T3-J1. The Neo-Tethys began evoluting during J2. Himalayan orogenic movement made Neo -Tethys closed and crust uplifted in large scale and striked-slip to form pull-apart basin. The tectonic evolutions showed the characteristcs of the accordion typle due to the crust were opened and closed mutually.