大陆盆地的聚敛-闭合过程研究:以塔里木盆地为例

印度与欧亚大陆第三纪以来碰撞汇聚,造成亚洲大陆内部强烈缩短变形。塔里木盆地如何发生相应的变形调节和应变分解,成为中亚板内构造的重要问题。塔里木陆块新生代以来被板内造山带及走滑断裂系环绕,盆地内部以刚性为特征,未发生强烈构造变形。区域大断裂与塔里木盆地的冲断、走滑构造边界共同作用,形成盆地边缘复杂的构造系。其新生代构造变形主要集中于盆地的构造边界上,4条构造边界显示差异性的运动特征和构造交切关系。盆地边缘构造带叠加并向盆内扩展,造成盆地总体上水平缩短,并发生应变分解。盆地内部发生沉积-构造分异,发育前陆盆地、前缘隆起、复合前陆盆地、拉分盆地等单元。其中,盆地西北缘及西南缘发生陆内俯冲,形成前陆盆地及前陆冲断带,对盆内构造演化有重要影响。区域构造研究表明,塔里木盆地新生代主要发生了4期区域构造变形,第三纪以来还发生顺时针旋转。大陆盆地构造边界上的运动组合、盆内不均匀阻挡和滑脱拆离,造成其变形扩展方式的差异,并影响盆内单元构造演化。因此,塔里木盆地是认识大陆盆地聚敛与闭合过程的天然实验室。

The shortening process and closure of a continental basin: a case study of the Tarim basin, Northwest China

The Tarim basin is the largest Cenozoic sedimentary depression north of the Tibet plateau. The Tarim basin is surrounded by Cenozoic intraplate orogenic belts. Contrasting with the spectacular uplift and spreading of the Tibet plateau, the relatively strong Tarim block generally has undergone little internal deformation during Cenozoic orogenic movements. The tectonic boundaries of Tarim basin show clear cutting or transfer relationships. Major fractures and marginal thrust and strike-slip fault systems characterize the basin margins. With the ongoing convergence and shortening between Tarim basin and the reactivated orogenic belts, the folding and thrusting deformation propagated from its northwest and southwest margins to the interior of the basin. As a result, the horizontal shortening led to a sedimentary and structural differentiation of the basin, with a foreland basin, a forebulge, a composite basin and a pull-apart basin being developed. In response to indentation of the Pamir wedge and tectonic movements along the Altyn Tagh fault, the Tarim basin underwent clockwise rotation about a vertical axis since the Tertiary. Therefore, it is suggested that the Tarim basin is one of the best natural laboratories for the understanding of deformation mechanisms associated with the continental basin and crustal shortening processes.