紫荆关断裂在太行山北段的特征及其发生发展过程的推论

    THE FEATURES OF THE ZIJINGGUANFRACTURE IN THE NORTHERN SECTION OF THE TAIHANG MOUNTAINS AND THE INFERENCE OF THE PROCESS OF ITS FORMATION AND EVOLUTION

    • 摘要: 六十年代初期,河北区调大队在太行山北段工作时,发现紫荆关到(涞水县)白涧之间存在一条断裂带,继而又发现此断裂带向南延伸到曲阳县灵山附近,向北经沿河城直指南口。通过综合研究,进一步发现在此断裂两侧,地层发育程度或地质历史有很大区别,因而提议命名为紫荆关大断裂,或称紫荆关—南口大断裂,亦称灵山—南口大断裂。七十年代初期引进卫星照片以来,由这条断裂及与之平行的西邻乌龙沟、北李庄两条主干断

       

      Abstract: The Zijingguan fracture was discovered and named by the Hebei Regional Geological Survey Brigade in the course of the 1:200000-scale regional geological survey in the northern section of the Taihang Mountains in 1959. In recent, years it has been found that the linear image of this fracture extends farther, constituting another important longitudinal fracture zone in the eastern part of China. An on-the-spot investigation of the northern section of the Taihang Mountains shows that the fracture zone consists of three parallel fractures of NNE-SSW trend: (1) the Zijingguan fracture at the eastern side, which extends northwards and is stopped by the pre-existing NEE-trending Yanhecheng fracure; (2) the Beilizhuang fracture at the western side, which extends northwards and disappears past the Lesser Wutai Mountains; and (3) the Wulonggou fracture in the middle, which stretches farthest. The three fractures combine to form the "Zijingguan fracture zone". Of these fractures, the Zijingguan fracture has a vertical throw of more than a thousand meters. It initiated at the end of the Jurassic; at that time its western block (footwall) was tilted by a big margin, thus resulting in a tectonic pattern of "tilted fault block" in the western part of the fracture. It was completed at the end of the Cretaceous; at that time it was mainly subject to horizontal torsion, therefore it is characterized by the nature of marked inheritance. Throughout geological history, the fracture has long been in the pivotal position of crustal uplift and subsidence since the late precambrian, so they have played an important controlling role, thus giving rise to utterly different geological structral backgrounds at opposite sides of the fracture.

       

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