塔里木中新生代盆地扩张和盆地俯冲与地幔柱

EXTENSION AND SUBDUCTION OF THE MESO-CENOZOIC TARIM BASIN AND THEIR RELATIONSHIP WITH MANTLE PLUME

塔里木盆地自二叠纪以来,历经盆地扩张和盆地俯冲以及陆内造山作用的过程。盆地扩张和盆地俯冲是与地幔柱活动相互关联的地质作用,即由于地幔柱的形成和演化,塔里木地区的岩石圈是一个降温过程。早二叠世时,由于热地幔柱上升活动,引起在大陆壳区首先形成巨大的热穹窿构造,再进一步发展演化,形成地堑和断陷盆地。晚二叠世—三叠纪,盆地中部因在早二叠世地幔柱物质喷发后,热上涌减小,再之,由于位于克拉通,地幔岩石圈减薄程度相对较低,古地温较低,达不到产生伸展断陷盆地的临界值,形成陆内坳陷盆地;在盆地边部,由于地幔物质上涌,由盆地中部向四周产生强大的挤压,天山和昆仑山山系快速隆升,向盆地大规模冲断,分别形成两个陆内前陆盆地。侏罗—白垩纪,塔里木地区的岩石圈是一个降温过程,由于热沉降,形成陆内坳陷盆地。新生代,该区经历一个相对较快的降温过程,这一过程对应着大陆聚合、俯冲、逆冲推覆、碰撞造山等各种汇聚—碰撞—挤压环境,由此造成塔里木盆地四周山系不断上升,山系向盆地仰冲,盆地俯冲。正是由于地幔柱的形成和演化,致使盆内扩张,盆边向山内俯冲,发生陆内造山作用。塔里木中新生代的原型盆地有:横张裂陷盆地(早二叠世);陆内前陆盆地和陆内坳陷盆地(晚二叠—三叠纪);陆内坳陷盆地(侏罗—白垩?

Since the Permian, the Tarim Basin had undergone basinal extension, subduction and intro-continental orogeny. Basinal extension and subduction was related to activity of mantle plume, formation and evolution of mantle plume resulted in geothermal decreasing of lithosphere in the basin. A huge thermal dome structure was firstly formed in continental crust due to rising of hot mantle plume during the Early Permian, and graben and fault basin were further formed. During the Late Permian to Triassic, intra-continental down-warped basin was formed in the central part of the basin as a result of thermal decreasing from mantle after eruption of mantle plume material in the Early Permian;however, strong compression was occurred from centre to outsides because of raising of mantle material, Tianshan and Kunlunshan were fastly uplifted and thrusted towards the basin, and two foreland basins were formed respectively. From the Jurassic to the Cretaceous, it was a thermal decreasing period in the basin, as a result, intra-continental down-warped basin was formed. It was a relative fast period for geothermal decreasing during Cenozoic, which corresponded with continental convergence, subduction, thrust-nappe and collisional orogeny in the area. Mountain system around the basin was uplifted continously and the basin was subducted. Just because of formation and evolution of mantle plume, it resulted in inner basinal extension, subduction and intra-continental orogeny. The protobasin in Meso-Cenozoic includes transverse extensional basin (Early Permian), intra-continental foreland basin and down-warped basin (Late Permian-Triassic), intra-continental down-warped basin (Jurassic-Cretaceous) and late foredeep basin(Cenozoic).