河西走廊西端黑山断裂运动学特征及其在构造转换中的意义

河西走廊西端北侧的黑山断裂不仅构成了河西走廊重要组成部分——酒西盆地的北部边界,同时也是青藏高原北部边界重要断裂——阿尔金断裂东端构造组成和转换的重要部分。通过对黑山断裂野外调查?典型断错地貌面的测量以及年代测定,获得了黑山断裂晚更新世以来的逆冲滑动速率为每年(0.26±0.06)mm,同时证实该断裂为一条以高角度逆冲为主要运动特征的断裂,其运动性质与阿尔金断裂存在明显的不同。结合对阿尔金断裂东端部运动学特征的讨论,总结前人在河西走廊西端酒西盆地内NW向断裂定量研究成果,得到河西走廊西端这些NWW向逆冲断裂和褶皱在平行于阿尔金断裂走向上的缩短速率总和为每年1.4~2.4 mm,这与阿尔金断裂东端部每年1~2 mm水平走滑速率相当,由此推断阿尔金断裂东端的左旋走滑被活动的逆冲断裂?第四纪褶皱隆起引起的地壳缩短吸收和转换了,阿尔金断裂在其东端部水平滑动速率逐步降低,断裂终止于河西走廊西端的宽滩山一带,而河西走廊西端酒西盆地北侧的黑山断裂与其走向上相联接的磴磴山断裂、金塔南山断裂可能共同构造了青藏高原朝NE向扩展的最前缘。

Kinematics Characteristics of Heishan Fault in the Western Hexi Corridor and Its Implications for Regional Tectonic Transformation

Located in the northern of the western Hexi Corridor, Heishan fault is the northern boundary of Jiuxi Basin and an important fault at the eastern end of Altyn Tagh fault. The vertical components of slip rates of (0.26±0.06)mm per year for Heishan fault by topographic profiling and dating age for alluvial fan were determined. Heishan fault is a high-angle reverse fault, which is different from the sense of motion of Altyn Tagh fault. Combined with the previous studies on the NW-striking faults in Jiuxi Basin, the total shortening rate of 1.4-2.4 mm per year along the direction parallel to Altyn Tagh fault in the western Hexi Corridor was constrainted, consistenting with the strike-slip rates of 1-2 mm per year at the eastern end of Altyn Tagh fault. Thus, it is inferred that the left-lateral strike slip at the eastern end of Altyn Tagh fault has been absorbed by the reverse faulting and folding of Quaternary crust in the western Hexi Corridor. The left-lateral strike-slip rates in Altyn Tagh fault decrease along the northeastern direction and the fault terminated near Kuantanshan in the western Hexi Corridor. Heishan fault, Dengdengshan fault and Jintananshan fault maybe comprise the most northeastern frontier of Qinghai-Tibet Plateau.