兰坪-思茅盆地原型的性质及演化

兰坪—思茅中生代盆地发育于滇西古特提斯多岛洋构造格局基础之上,其形成演化与特提斯—三江造山带的构造演化密切相关.对盆地形成早期火山岩和盆地不同时代砂岩的构造地球化学分析表明,兰坪—思茅中生代盆地的原型主要具有大陆边缘裂谷盆地的性质.其演化经历多阶段复杂的演化历程,中三叠世,伴随中特提斯洋开启,地壳拉张裂陷,兰坪—思茅中生代盆地原型开始形成.晚三叠世末—早侏罗世,由于受中特提斯关闭引起的造山运动的影响,下侏罗统普遍缺失.从中侏罗世开始,由于新特提斯洋开启,盆地再次下沉接受中侏罗统—白垩系的沉积.喜马拉雅造山运动,使本区地壳大面积隆升,兰坪—思茅盆地原型遭受强烈变形,继而在中生代裂谷盆地基础上叠加了新生代的拉分盆地.构造演化控制了盆地沉降作用、沉积作用、火成活动和构造格架.

Nature and Evolution of Lanping-Simao Basin Prototype

Lanping-Simao Mesozoic Era basin is a sedimentary basin that was formed on the base of Palaeo-Tethys multi-island ocean framework,closely related to the tectonic evolutions of Tethy-Sanjiang orogenic belt.The results of tectonic geochemistry analysis of volcanic rocks and sandstone show that Lanping-Simao basin prototype possesses the natures of continental margin rift basin.Its tectonic evolution is multistaged and complicated.The basin prototype was formed during middle Triassic Epoch accompanying the open of Mid-Tethys ocean.The closing of Mid-Tethys made the crust be deformed and lower Jurassic Series hiatused during the end of Late Triassic Epoch-Early Jurassic Epoch.The Neo-Tethys began evolution during Middle Jurassic Epoch,which made the basin prototype subside again and deposit Middle Jurassic Series-Cretaceous System.Himalayan orogenic movement made Neo-Tethys closed and crust uplifted in large scale,in which the basin prototype was deformed to form fractures and folds and characteristic ramp structures,then superposed Cenozoic Era pull-apart basins.The tectonic evolutions controlled the sedimentation,pyrogenesis and structure framework of the basin.