帕米尔东北缘大型右旋走滑断层的雏形：来自克孜勒苏河走廊晚第四纪变形的约束

The Tarim-Alai region situates between the Pamir-Western Kunlun and southern Tian Shan orogens. Geologic and geomorphic mapping, geodetic GPS velocities, and modern earthquake distribution indicate that the recent convergence is concentrated along a nearly eastern-trending zone: the Pamir Thrust System in the Alai Valley, whereas the southern Tian Shan Thrust System in the Tarim Basin. How the strain localization shifts from the Pamir front to the southern Tian Shan front, however, has not been investigated.. Located to the northeastern of the Pamir, the Kezilesu Corridor is the shift place of the strain localization. Because the northward extruding of the Pamir to the west and the southward pushing of the southern Tian Shan to the east can produce a dextral shear stress, we speculate that the strain may be spatially transferred through an incipient dextral strike-slip fault. According to this model, i) the deformation in the shear zone is dominated by thrusting and folding, instead of significant strike-slip faulting. ii) The thrusts and folds will be rotated clockwise compared to those beyond the shear zone, moreover, the rotation angle will increase from the shear zone edge to the inner. iii) From the inner to the edge, the strain will be gradually localized. iv) From west to east, the strain absorbed by the Pamir Thrust System will decrease gradually, compared to the increasing tendency of the southern Tian Shan Thrust System.. Our proposal suggests to constrain the spatial extension of active structures and strain partition along the strike of the Kezilesu Corridor based on geologic and geomorphic mapping, deformed fluvial terraces measurements and dating, as well as seismic profiles interpretation, all of which can serve to examine the above model, determine the shear zone boundaries, and have insight into the basic shift mode of strain localization.

塔里木盆地-阿莱谷地是帕米尔-西昆仑与南天山相向对冲的区域。活动构造填图、GPS数据分析和地震分布表明，现今构造变形在阿莱谷地集中在帕米尔冲断带，在塔里木盆地则集中在南天山冲断带。区域应变如何从帕米尔山前过渡至南天山山前至今未有很好的讨论。帕米尔东北缘的克孜勒苏河走廊是区域应变过渡的位置。由于走廊以西帕米尔的向北逆冲和走廊以东南天山的向南逆冲会产生右旋剪切力，推测区域应变可能通过一具有应变转换性质的右旋剪切带，亦即孕育中的走滑断层发生了空间上的过渡。由该模式，剪切带内构造变形以发生系统性顺时针旋转的逆断层和褶皱为主；应变在剪切带中部最为弥散，向边缘逐渐集中；帕米尔和南天山冲断带吸收的应变呈此消彼长的趋势。本申请拟通过地质地貌填图，变形河流阶地测量、定年和地震反射剖面解析对走廊内活动构造的空间展布特征、应变沿走向的分配特征进行限定，对上述模式进行检验，并界定剪切带的范围。

塔里木盆地-阿莱谷地是帕米尔-西昆仑与南天山相向对冲的区域。已有的活动构造填图资料、GPS观测数据和强震分布表明，现今构造变形在阿莱谷地集中在帕米尔前陆冲断带，在塔里木盆地则集中在南天山前陆冲断带。那么由西向东，区域应变是如何从帕米尔山前过渡至南天山山前的？过渡带内现今变形由哪些构造调节，具有怎样的变形特征？围绕上述问题，我们选择位于区域应变过渡位置的克孜勒苏河走廊为研究区，在前人已有成果的基础上，综合运用遥感影像解译、野外地质地貌填图、变形河流阶地地形测量和定年及石油物探剖面解析等方法和手段，对走廊内活动构造的空间展布、变形机制和变形速率进行了约束。取得的成果如下：（i）建立了河流阶地的地貌框架和年代序列，阶地的形成与全球性气候变化和帕米尔、南天山地区的冰进/冰退事件存在很好的对应关系；（ii）主要活动构造吸收的缩短速率介于0.1-4.6 mm/a，总缩短速率为6-9 mm/a，与GPS获得的现今区域会聚速率相当；（iii）帕米尔前陆冲断带和南天山喀什-阿图什褶皱带的剖面结构和滑脱层层位存在显著差异，大致以克孜勒苏河为界，河道以南的构造属于帕米尔前陆冲断体系，河道以北的构造则属于南天山前陆冲断体系；（iv）另外，我们对研究区内广泛发育的、与褶皱生长相伴生的弯滑断层和弯矩断层的地貌表现、形成条件及其在褶皱变形中所起的作用进行了系统分析和总结。通过上述研究，我们认为克孜勒苏河走廊是区域应变发生转换的位置，转换带（右旋剪切带）的范围大致从吾合沙鲁向斜至木什背斜。