太行山隆起南段新构造变形过程研究

基于TM遥感影像解译和断裂滑动矢量资料的野外观测,结合年轻地质体热同位素和放射性同位素年代学测试结果分析,重点描述了太行山隆起南段构造地貌特征,划分了新构造变形阶段,确定了新构造应力场及其转换历史。研究表明,新近纪以来,太行山南段经历了两期重要的引张变形时期。中新世中晚期,伴随华北地区广泛的基性火山喷溢活动,太行山南段受近NE-SW向引张应力作用,构造变形集中在南段东缘和南缘断裂带上。上新世至早更新世时期,强烈的NW-SE向地壳引张导致太行山隆起南段夷平地貌的解体和地堑盆地的形成。自中晚更新世以来,太行山南缘断裂带成为新构造变形的主要边界带。断面滑动矢量分析和山前年轻冲积扇体和小冲沟沿断裂错移特征分析,表明太行山南缘断裂带是一条斜张左旋走滑边界断裂带,引张方向为NW-SE至NNW-SSE.从区域大地构造角度,中新世中国东部NE-SW向拉伸作用与东部太平洋板块向西俯仲导致的弧后扩张动力过程有关;而上新世以来新构造变形是与青藏高原快速隆升及其向东构造挤出作用有关。 

NEOTECTONICS IN THE SOUTHERN PART OF THE TAIHANG UPLIFT,NORTH CHINA

Based on TM remote-sensing image interpretation and field observation of slip vectors of faults,coupled with the thermal isotope and radioactive isotope chronological studies of younger geologic bodies,this paper mainly describes the morpho-structural features in the southern segment of the Taihang uplift,defines the phases of neotectonic deformation and determines the neotectonic stress field and its transition history.Studies indicate that in the Neogene the southern segment of the Taihang Mountains experienced two major phases of extension.In the mid-late Miocene the area was subjected to nearly NE-SW extension,concomitantly with extensional eruption of basic volcanic rocks in North China.The extension was concentrated in fault zones on the eastern and southern margins of the area.During the Pliocene to early Pleistocene strong NW-SE crustal extension resulted in disintegration of the planation geomorphology and formation of a graben basin in the area.Since the mid-late Pleistocene the southern Taihang Mountain marginal fault zone has become a main boundary zone of neotectonic deformation.Analyses of fault plane slip vectors and displacement features of younger piedmont alluvial fans and small gullies along the fault suggest that the fault zone is an oblique-extensional,sinistral strike-slip boundary fault znoe,with the extension oriented in a NW-SE to NNW-SSE direction.In the tectonic context,the NE-SW extension in eastern China in the Miocene is related to the dynamic process of back-arc spreading resulting from westward subduction of the Pacific plate to the east,while the neotectonic deformation since the Pliocene is related to the rapid uplift of the Qinghai-Tibet Plateau and eastward tectonic extrusion due to the late-stage India-Eurasia collision.