Abstract: The southern Alashan margin fault bundle is composed of 5 faults which strike EW, converge westward and splay eastward. Each fault of the fault bundle extends more than the 100km, controls the distribution of EW-trending Quaternary basins, and is featured with sinistral slip since the late Quaternary. The western part of the fault bundle-the Jintananshan Fault, tends to meet with the Kuantanshan Fault-the east part of the Altun Fault and has some relations to the Wenzhushan uplift in the transformation. According the spatial correlation, it is believed that the Jintananshan Fault as well as the whole fault bundle is the eastward-extending part of the Altun Fault. The special modality of the fault bundle, which spreads out eastwards, is in favor of decomposing and absorbing the slip movement, which is normal at a strike-slip fault's ends. The sinistral strike-slip movement of the fault bundle is the result of the Altun Fault extending further eastward, which might have begun between the end of the early Pleistocene and the beginning of the middle Pleistocene.

Key words: the Altun Fault, structural transformation, end structure, Alashan

摘要： 阿拉善地块南缘发育了由5条走向近EW、向西收敛、向东撒开的断裂组成的断裂束,每条断裂长度一般>100km,控制第四纪盆地呈EW向长条状展布,卫片上线性影像清晰,晚第四纪以来表现出左旋走滑活动的特点。断裂束西段的金塔南山断裂与阿尔金断裂带东段的宽滩山段趋于交会,并与文殊山构造隆起之间构成构造转换关系。分析认为金塔南山断裂以及整个阿拉善南缘断裂束是阿尔金断裂左旋运动的东延部分,断裂束在平面上“帚状”的、向东撒开的构造样式有利于走滑运动量的分解、消减和吸收,符合走滑断裂末端的构造特点。阿拉善南缘断裂束的左旋走滑活动有可能是阿尔金断裂带进一步向东扩展的结果,其时代可能发生于早更新世末-中更新世初。

关键词: 阿尔金断裂, 构造转换, 尾端构造, 阿拉善