柴达木盆地北缘中、新生代盆地性质及构造演化

运用沉降史和平衡剖面技术分别对柴北缘中、新生代盆地垂向上的升降史和水平方向上的伸缩史进行定量研究,并结合区域地质背景对研究结果进行分析。结果表明:自中生代以来,柴北缘的构造演化可分为中生代(J—K)演化阶段和新生代(E1+2以来)演化阶段。中生代演化阶段(J1—J2),沉降史曲线具有伸展盆地特征,平衡剖面恢复结果也以伸展为主,最大伸展率和伸展速率分别达1.9%和19.48 m/(M a.km)。这是受柴北缘周缘地块和柴达木地块运移差异引起的拉张应力场控制,因而具有伸展盆地性质。此外,由于柴达木地块的自身旋转,3个坳陷的沉降速率、伸缩率和伸缩速率也存在差异。新生代演化阶段(E1+2以来),沉降史曲线具有前陆盆地特征,平衡剖面恢复结果也以压缩型为主,最大压缩率和压缩速率分别为4.96%和14.09 m/(M a.km),这是受印度板块和亚欧板块相互碰撞所引起的挤压应力场控制,因而具有前陆盆地性质。此外,受喜山运动各期的影响,各坳陷沉降速率和伸缩率均具有“幕式”渐进特点。

The Meso-Cenozoic Basin Type and Tectonic Evolution in the Northern Margin Region of the Qaidam Basin

The subsidence history and the balanced cross sections are applied in this paper.The former is used for researching the up and down history in the vertical direction,and the latter is used for researching the extensional and compressional history in horizontal direction.The analysis of the quantitative research result with the regional geology background proves that tectonic evolution can be divided into Mesozoic(J-K)and Cenozoic(start from E_(1+2))phases from Mesozoic in the Northern Margin Region of the Qaidam Basin.In the Mesozoic(evolution) phase(J_(1)-J_(2)),the subsidence history curve has the quality of extensional basin,and the restoration result of the balanced cross sections has the quality of extension,too.The maximal extension ratio of it is 1.9% and the rate is 19.48 m/(Ma·km).The extension stress field is aroused by the difference of the Qaidam plate and the adjacent plates' movements.Besides,because of the self-circumgyrate of the Qaidam plate,the subsidence rates and the extension ratios are different in the three sags.In the(Cenozoic) evolution phase,the subsidence curve has the character of the foreland basin,and the restoration(result) of the banlanced cross sections has the quality of compression,too.The maximal compression ratio of it is 4.96% and the rate is 14.09 m/(Ma·km).The compression stress field is(aroused) by the collision between the India plate and Eurasia plate.Furthermore,because of the Himalayan movement,the subsidence rates and extension ratios have the character of the graduate "episode ".