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天山山脉位于中国西部,南北两侧分别与塔里木盆地和准噶尔盆地相邻.在天山山脉北麓,由于持续的冲断和褶皱作用,形成了一系列走向东西近平行排列的活动背斜构造.地质观测表明,这些背斜在平均到大致1 Ma时间上的水平缩短速率在2.1~5.5mm/a,但平均到大致(10±2)ka以来的水平缩短速率仅为(1.25±0.5)mm/a.在时间上,发生天山山脉北麓冲断-褶皱速率下降与末次冰期以来大量冰消融的时间基本一致.为了探讨这些活动背斜在不同时间窗口内水平缩短速率变化的机制,本文建立了一个二维粘-弹-塑性有限元模型.模型考虑了天山山脉水平挤压和地表沉积-剥蚀相互耦合作用.模拟结果显示,在恒定的水平推挤速度下,当地表沉积-剥蚀作用相对较弱时,天山山脉地壳的缩短主要被其北麓的断层相关褶皱吸收,其缩短速率与平均到大致1 Ma时间尺度上这些背斜的水平缩短速率基本一致;然而,随着地表沉积-剥蚀作用不断加强,仍然在相同的水平速率推挤下,天山山脉地壳的缩短却不断向山体内部转移,导致天山北麓的断层相关褶皱水平缩短速率减小,并与平均到大致(10±2)ka以来的水平缩短速率相近.这表明在大陆内部活动构造带,地表的沉积-剥蚀作用对应变在不同构造带的调配起着重要的动力学作用.就天山山脉而言,如果业已存在的天山腹地及其前陆变形带在末次冰消期的气候变化可以用地表沉积-剥蚀作用的强化来代表,那么在平均到大致1 Ma和(10±2)ka时间尺度上,天山山脉北麓观测到的地壳缩短变化可能与气候变化所控制的沉积-剥蚀地表过程有关.
The Tianshan Mountains are located in the western part of China and adjacent to the Tarim Basin and the Junggar Basin, respectively, on the north and south sides of the Tianshan Range, where a series of anticlinal anticlinal structures are formed that are nearly parallel to each other due to continuous thrusting and folding. Observations show that the horizontal reduction rate of these anticlines is 2.1-5.5 mm / a over an average period of about 1 Ma, but the horizontal shortening rate is only (1.25 ± 0.5) mm / In time, the thrust-fold reduction of the northern foot of the Tianshan Mountains coincides with the time of massive ice ablation since the last ice age.In order to investigate the mechanism of the horizontal shortening rate change of these active anticlines in different time windows, A two-dimensional visco-elastic-plastic finite element model is proposed in this model, which takes into account horizontal compression and surface sedimentation-erosion interaction in the Tianshan Mountains.The simulation results show that under the constant horizontal pushing speed, The weakening of the crust of the Tianshan Mountains resulted in the shortening of the crust mainly absorbed by fault-related folds at the northern foot of the Tianshan Mountains. The shortening rate and the horizontal shortening rate of these anticlines on an average time scale of about 1 Ma However, with the surface sedimentation-denudation strengthening, the shortening of the crust of the Tianshan Mountains continued to move toward the interior of the mountain under the same horizontal rate of thrusting, resulting in a decrease in the rate of fault-related fold reduction at the northern foot of the Tianshan Mountains, Which is close to the horizontal reduction rate from the average to the (10 ± 2) ka, suggesting that the depositional-denudation effect on the surface plays an important dynamic role in the tectonic belt mobilization. For the Tianshan Mountains, if the existing climate change in the Tianshan Mountains hinterland and its foreland deformation zone during the last ice age can be represented by the enhancement of surface sedimentation-denudation, then on average to about 1 Ma and (10 ± 2) ka On the time scale, the observed shortening of the crust in the northern foot of the Tianshan Mountains may be related to the sedimentation-erosion surface processes controlled by climate change.