摘要:利用天然地震环境噪声成像研究柴达木盆地及邻区的岩石圈结构，利用工业地震剖面研究新生代构造变形的几何学与运动学特征，在此基础上讨论柴达木盆地新生代的成盆动力学过程与演化。柴达木盆地及邻区的岩石圈表现出向南和向北挠曲的特征。其中，东昆仑—可可西里地区地壳深度30～40 km 的低速层向北抬升，可与柴达木盆地内部深度15 km 左右的低速区相连接，反映了东昆仑—祁漫塔格山向柴达木盆地的逆冲推覆作用，因此在岩石圈尺度上，柴达木新生代成盆动力学过程与前陆盆地是相似的，表现为构造负荷引起的挠曲沉降。柴达木盆地新生代构造变形受控于柴西南和柴北缘两期冲断系统，柴北缘冲断系统形成于古新世—始新世路乐河—下干柴沟期，主要记录于祁连山山前、阿尔金山山前北段及冷湖和鄂博梁深层；柴西南冲断系统形成于早中新世下油砂山期以来，现今盆地南部的北西向构造带和盆地北部的冷湖和鄂博梁浅层构造都属于这期冲断系统。由于柴西南冲断系统的前锋构造已扩展至柴达木盆地北缘，并受到阿尔金山和祁连山的阻挡，缺少稳定的台盆区，因而使得柴达木盆地新生界不发育前陆盆地特有的楔状沉积结构。柴西南和柴北缘两期冲断系统的叠加，不仅使得柴达木新生代构造变形在时间和空间上呈现有次序的分布，也使得新生代盆地呈现出开启到封闭的演化格局，从而对新生界油气生成和聚集产生了重要影响。
关键词: 成盆动力学/
岩石圈/
冲断系统/
新生代/
柴达木盆地
Abstract:The lithospheric structure of Qaidam Basin and its surrounding areas is revealed through application of nature earthquake ambient noise tomography. The geometric and kinematic characteristics of Cenozoic structural deformation, and its time and space distribution sequences are studied by the use of industry seismic interpretations and advanced fault-related folding methods. On the basis of above work, the Cenozoic basin-forming dynamics mechanism and evolution of Qaidam Basin are discussed. The lower crust and upper mantle lithosphere are obviously deflected toward the eastern Kunlun range in the south and Qilian range in the north. The low velocity layer in middle crust in the eastern Kunlun and Hoh Xil areas, located at depth of 30～40 km, uplifts from south to north, and can be connected with the low velocity layer in Qaidam Basin, located at depth of 15 km, which maybe reflects the large-scale thrusting from the eastern Kunlun and Qimen Tagh ranges toward Qaidam Basin, so in the lithosphere scale, the deep dynamics process of Qaidam Basin is characterized by the flexural subsidence by structural load, which is similar with the foreland basin. Cenozoic structural deformation of Qaidam Basin are dominated by the southwestern Qaidam thrust system and the northern Qaidam thrust system. The northern Qaidam thrust system developed since the deposition of the Lulehe-Xiaganchaigou Formations in Paleocene-Eocene, which is mainly recorded in the piedmont of Qilian and Altyn Tagh ranges and the deep structures of Lenghu and Eboliang belts in the northern Qaidam. The southern Qaidam thrust system developed since the deposition of Xiayoushashan Formation in the Early Miocene, which includes the current NW-SE trending structural belts and the shallow structures of Lenghu and Eboliang belts. So the front of the southwestern Qaidam thrust system had extended to the northern margin of Qaidam Basin, and was resisted by the Altyn Tagh and Qilian ranges, it is the main factor that disabled the development of wedge deposition form in Cenozoic Qaidam Basin. The imbricate of these two stages of thrust systems not only caused the orderly arrangement of Cenozoic structural deformation in space and time, but also controlled significantly hydrocarbon migration and accumulation.
Key words:Basin-forming dynamics/
Lithosphere/
Thrust system/
Cenozoic/
Qaidam Basin
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