卡拉库姆盆地晚二叠世—三叠纪的构造属性讨论

Discussion of structural attributes for Karakum Basin in Late Permain-Triassic

卡拉库姆盆地位于中亚地区图兰地台南部，北西走向，是中亚地区最重要的含油气盆地之一。对于盆地晚二叠世—三叠纪的构造属性一直都存在着很多争论，我们根据钻井、地球物理及露头资料，认为卡拉库姆盆地是以增生杂岩为基底形成的一个沉积盆地，晚二叠世—三叠纪具有弧后裂谷的性质。卡拉库姆盆地前侏罗纪的构造演化分为4个阶段：1）石炭纪之前古特提斯洋壳开始俯冲增生；2）石炭纪—早二叠世形成丝路弧；3）晚二叠世—三叠纪马什哈德—北帕米尔弧形成，卡拉库姆盆地处于弧后拉张的位置；4）晚三叠世末伊朗等地块与欧亚大陆碰撞，卡拉库姆盆地进入短暂的周缘前陆盆地阶段。其晚二叠世—三叠纪的沉积中心在北阿姆河坳陷，木尔加布坳陷和科佩特山前坳陷，沉积环境主要为陆相，三叠纪发生海侵，部分地区接受海相沉积。岩石类型主要为陆源碎屑岩、火山岩及少量灰岩。

Karakum Basin, which is located in the south of Turan platform, NW trending, is one of the most important petroliferous basins in central Asia. The tectonic attributes of basin in Late Permian-Triassic has always been around a lot of controversy. According to the drilling, geophysics and outcrop data, we think that the Karakum Basin is a sedimentary basin which has a basement with accretionary complexes. It has nature of back-arc rift in Late Permian- Triassic. The evolution of Pre-Jurassic in Karakum Basin can be divided into four stages： 1 ） Paleotethys oceanic crust began to subduction before Carboniferous; 2）Silk Road Arc formed in Carboniferous-Early Permian; 3）Karakum Basin is located in the back-arc extensional position when Mashhad-North Pamir Arc formed in Late Permian-Triassic; 4）Karakum Basin became a peripheral foreland basin in short week stage when Iran blocks collided with Eurasia in the end of Late Triassic. The depocenter of basin is North Amu-Darya, Murgab and Kopet Dag foredeep. The depositional environment is conventional facies, and some areas received transgression and became marine in Triassic. Rock types are mainly siliciclastic rocks, volcanic rocks and a small amount of limestone.