摘要
藏南洛扎地区洛扎断裂属于区域上定日—洛扎断裂的东段部分,是喜马拉雅造山带中一条重要的断裂,但其总体研究程度较低。运用地质填图和构造解析的方法研究了洛扎断裂的几何形态、运动表现和活动历史等,讨论其在喜马拉雅造山带构造格局形成中的意义。主要认识如下:(1)洛扎断裂现今主要表现为一条规模大的脆性-脆韧性断层,SWW—NEE走向,高角度倾向NNW。断层带内发育劈理带、断层泥、构造角砾岩等。运动性质主体表现为正断层。(2)洛扎断裂的南北两侧地块具有显著不同的变形特征,南侧为平缓的大型背斜-向斜构造,北侧为近NWW—SEE走向的倒转褶皱-断层构造。(3)洛扎断裂经历了多期活动,中生代正断活动,古近纪逆冲活动,中新世韧性伸展,中新世晚期逆冲活动以及上新世—第四纪正断活动。现今断层展示的更多是最后一期活动的形迹。(4)依据其规模大、多期活动性、两盘构造变形与沉积的系统差异性等肯定了其作为构造分区断层而存在。(5)洛扎断裂和藏南拆离断层(STD)在研究区均有出露,局部二者出露线近于重合,但洛扎断裂以高角度断面切割了平缓的STD。洛扎断裂是比STD具有更悠久地质历史的区域性断层,只是后者中新世以来的活动性更多受到关注。
Lhozhag fault,the eastern segment of the famous Dingri.Lhozhag Fault,is a tectonically significant structure in the Himalayan orogen,but it remains poorly constrained so far.Geologic mapping and structural analysis of Lhozhag fault in Lhozhag area,southeastern Tibet,were carried out to reveal its geometry,kinematics,evolutional history and tectonic significance.The major structural features of Lhozhag fault are described as follows:(1)Lhozhag fault is now mainly characterized by a large brittle,brittle.ductile normal fault with a SWW.NEE strike and steep NNW dipping.The fault zone materials are comprised of cleavages,fault gouge,fault breccia,etc.(2)Two blocks in Tethys Himalaya unit separated by Lhozhag fault have significantly different deformation characteristics,the south with gentle deformation,and the north with strong deformation.(3)Lhozhag fault has experienced five deformation events,i.e.normally faulting during the Mesozoic,thrusting during the Paleogene,ductile extension during the Miocene,thrusting during the late Miocene,and normally faulting during the Pliocene and Quaternary.Present fault features show more of the last episode of the activities.(4)Lhozhag fault on its large scale,multi.phase activities,and controlling the deformational and sedimentary differences between the northern and southern blocks,reveals that it plays the role of separating tectonic units on Himalayan orogeny.(5)Both Lhozhag fault and the south Tibetan detachment fault(STD)outcrop in Lhozhag area,and in some places,they are close to each other.Field data show steep Lhozhag fault has cut gentle STD.Lhozhag fault is a regional fault with a longer geological history than STD,but the latter's activities since Miocene have attracted more attention.
作者
刘顺
夏特
武梅千
周俊
王源
魏明浩
LIU Shun;XIA Te;WU Meiqian;ZHOU Jun;WANG Yuan;WEI Minghao(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation of Ministry of Natural Resources(Chengdu University of Technology),Chengdu,Sichuan 610059,China)
出处
《现代地质》
CAS
CSCD
北大核心
2019年第1期1-12,共12页
Geoscience
基金
中国地质调查局地质调查项目(12120114083401)
关键词
洛扎断裂
区域性断层
多期活动
藏南拆离断层
ESR测年
Lhozhag fault
regional fault
multi-phase activity
south Tibetan detachment fault
ESR dating
