关键词: 碰撞构造, 同位素年龄, 盆地改造, 塔里木盆地

Abstract:

Rock and isotopic age of the collision structures in Pamir region have recorded the movement of Indian plate toward Asian plate, which has experienced subduction and consumption of Neo-Thetys (113±1.5Ma-71.1±1.4Ma), collision of Indian and Asian plates(36.95±1.2Ma) and continuous squeezing after collision (6.69-6.80Ma). The Jurassic-Cretaceous in the southwestern Tarim Basin/Paleogene foreland basin, located in front of the Pamir thrust zone, have been reformed by the collision of Indian and Asian plates, and only the Maigaiti slope zone and Tazhong-Bachu frontal uplift zone have survived. The subsidence center of the Miocene-Quaternary foreland basin has migrated northward to Yecheng-Kashi where 5000～6000m of coarse clastic sediments have been accumulated as a result of rapid subsidence. Kuqa Meso-Cenozoic foreland basin on the southern side of Tianshan orogenic belt has relatively complete structures with smaller reformation than that in southwestern Tarim, hence the Yiqikelike-Kelasu Jurassic-Cretaceous/Paleogene foredeep subsiding zone, Qiulitage-Yaken slope zone and Yaha-Tabei fontal uplift zone have been preserved. Most of the Triassic-Jurassic/Early Cretaceous strata have been transformed into thrust fault and fault-bended and fault-extended fold belts, as well as the aggrading deformable zone of detachment faults and decollement folds in Qiulitage-Yaken slope zone during the Miocene collision. Later, they have been preserved by the superimposition and overlap of the southward migrating Baicheng-Yangxia Pliocene-Quaternary sag, thus they have been provided with the conditions for the formation of large gas accumulations. During the squeezing and strike-slip displacement stages after the Miocene collision of Indian and Asian plates, deep in-situ deformable bodies or anticlines, such as Yingjisha and Mingluyao etc. have been formed in Kashi depression, and in-situ folded deformable structures of collision stage (stage Ⅱ) might also exist in deep Cretaceous-Lower Tertiary in Atushi anticline, Kelasu anticline, Talanghe and Alabulake in west Tianshan mountain front. These structures should be the main exploration targets in Tarim basin.

Key words: collisional structure, isotopic age, basin reformation, Tarim Basin