【作者】 钱俊锋；

【导师】 肖安成； 杨树锋；

【作者基本信息】 浙江大学 ， 构造地质学， 2008， 博士

【摘要】 南天山西段冲断带和帕米尔冲断带形成于新生代晚期,并在塔里木盆地西北缘的喀什地区西部交接,彼此叠加以后导致各自构造要素发生交切、叠置、干涉和转换,冲断带结构异常复杂,使其成为前陆冲断带构造变形分析和叠加构造解析的最有利地区,深部地震资料的成像品质差以及地质结构研究程度低下是制约该区油气勘探的主要因素。因此,对这两个冲断体系的空间结构和形成过程进行研究,再现其中、新生代的构造演化历史,是塔里木盆地以至于中亚地区非常重要的科学问题,并对油气勘探具有一定的指导意义。本文在结合野外地质调查、地球物理、天然地震及钻井等大量实际资料分析的基础上,运用现代构造解析和地质建模理论,对塔里木盆地西北缘南天山西段冲断带和西昆仑帕米尔冲断带的地质结构及演化历史进行了研究,并建立起研究区的构造地质模型,再现了两大冲断体系的空间结构和彼此叠置关系,为中、新生代的盆地演化历史提供了分析基础和初步的结论。在浅层构造解析的基础上,通过对天然地震资料的数据分析,完成了西昆仑(帕米尔)与南天山两大造山带深部俯冲和浅层推覆的空间大地构造模型。通过研究,主要取得以下一些创新性的研究成果:(1)认为造成南天山西段冲断带横向差异性的主要控制因素有两点:一是中生代形成的控制断陷分布的断裂系统(费尔干纳断裂的一部分)的展布规律,这些断裂控制了侏罗纪沉积的分布;二是南天山和帕米尔构造系统空间对接位置在各个不同区域会改造南天山冲断系统的平面、剖面形态和构造体系的分布。并据此将南天山西段冲断带的构造变形划分为东段、中段和西段三个区段,并综合利用多种资料,对其进行了详细的中尺度构造解析。(2)在多条件约束下,通过多剖面的解析和结构分析,建立了塔里木盆地西北缘不同区段的2D构造变形模型,为本区的基础结构分析研究和油气勘探实践建立了较可靠的依据和标准。对研究区各个构造单元的重点剖面进行正演模拟和反演恢复,计算出南天山西段冲断带东区的缩短量为32.64～49.1km,缩短率为40.5%～50.51%,新生代以来南北地壳平均缩短速率为9.12mm/a～13.72mm/a;中部的缩短量为24.23km,缩短率为34.7%,地壳平均缩短速率为6.77mm/a。乌泊尔地区缩短量为32km,缩短率为40.2%,地壳平均缩短速率为7.17mm/a。(3)认为库孜贡苏断陷盆地自西向东发育多个不对称的侏罗纪箕状断陷,断陷结构为西断东超,说明该盆地形成时主要物源来自于西部的“乌拉根隆起”,由此揭示了南天山西段冲断带东西部分古生界分布差异性的原因。新生代以来盆地受印藏碰撞的影响发生了构造反转。(4)完成了三条穿过两大冲断体系表现浅层冲断结构的区域地质剖面,认为帕米尔冲断系统的前锋为一弧形构造带,类似于一个表层的推覆体直接覆盖在南天山冲断带的冲断片之上,二者形成了交错叠置的关系;而南天山冲断带则大多形成深层次的冲断褶皱作用。从地理上划分了南天山和帕米尔冲断系统的构造分界线,即为西部帕米尔冲断系统前锋弧形构造带以北的克孜勒苏河,往南沿克拉托-明尧勒背斜带以北断裂至喀什背斜带南侧恰克乌克达里亚河一线。(5)通过对天然地震剖面的解释,探索了南天山造山带、西昆仑(帕米尔)造山带和塔里木(塔吉克)地块的岩石圈大地构造关系,认为在东西两侧,塔里木(塔吉克)地块为南北直接俯冲于西昆仑(帕米尔)造山带和南天山造山带之下的双向俯冲模式;在中部地区,西昆仑造山带在帕米尔地区形成构造结并仰冲于南天山造山带的前陆冲断带之上,形成了两个新生代复活的巨型造山带,以及两大造山带与塔里木(塔吉克)地块之间的俯冲和对接关系,形成了独特的“盆一山”耦合体系。更多还原

【Abstract】 The western segment of South Tienshan and Pamir foreland fold and thrust belts were formed during Late Cenozoic.They met with each in Kash area,northwest of Tarim basin,causing the overlapping,cutting,interfering and transforming of structures with each other,which resulted in a more complex system.Because of the complexity in structure in Kash area,it become one of the best places for structural analysis of the foreland fold and thrust belts and overlapped structures.However,the restriction of low quality of seismic profiles in the deep part and less knowledge of the subsurface structure makes the exploration of oil and gas of this area still in a lower level.Hence,researches of spatial structures,formation processes and Mz-Kz tectonic history of these two fold and thrust systems play an important role in the researches of Tarim basin and central Asia and can also guide the exploration of oil and gas.Based on analysis of field-survey geological data,geophysical data,natural earthquakes and well data,the writer applied modern theories of structural analysis and geological modeling to the Kash area,and established structural geological model. From the model,it is readily to see the spatial structures and overlapping relationship of the two fold and thrust systems.It is also a basis for research of Mz-Kz tectonic evolution history of the basin.After detailed structural analysis of the shallow part and the natural seismic data,a tectonic model of the West Kunlun(Pamir) and South Tienshan,from deep-level subduction to shallow-level thrusting was established. After this study,some innovative results are listed below:(1) There are two main factors might take responsibility for the lateral variability of the western segment of Southern Tienshan fold and thrust belt.One is the Mesozoic fault system(a part of Feierganna fault) which controls the distribution of fault subsidences and the Jurassic sequences.The other factor that causes the lateral variability is the spatial relationship of South Tienshan and Pamir.That is,in different parts of the western segment of South Tienshan,Pamir would influence the thrust pattern of South Tienshan differently,including the pattern in map view,the cross-section structures and the structural domains.Based on those,the authors divided the western segment of South Tienshan into three different parts from east to west,integrating and synthesizing all kinds of data available,detailed medium-level structural analysis are done to different part of western segment of South Tienshan.(2) Constrained by several conditions,structural analysis is made to build a 2D structural model for the different parts of the northwestern margin of the Tarim basin. This provides a basis for the structural analysis and oil and gas exploration in the study area as detail as possible.The author chose several important cross sections through each tectonic unit for forward modeling and inversion modeling and calculated the structural shortening amounts and shortening rates of the different parts of the western segment of South Tienshan and Wuboer fold and thrust belts.The shortening amount of the east part is 32.64-49.1km,with a 40.5%-50.51%shortening ratio.The S-N shortening rate of the crust in Cenozoic is 9.12-13.72mm/a.The shortening amount of the middle part is 24.23km,with a 34.7%shortening ratio and a S-N 6.77mm/a shortening rate of the crust in Cenozoic.The shortening amount,ratio, rate of of Wuboer area is 32km,40.2%,7.17mm/a,respectively.(3) The Kuzigongsu fault subsidence has several asymmetric half-graben depressions from west to east.These half grabens are characteristic of west-faulting and east-overlapping.According to this phenomenon,the source of the sediments may be mainly from "Wulagen Uplift" to the west when the basin formed.During the Cenozoic,the basin was inversed affected by India-Tibet collision.(4) Three long cross-sections across the two fold and thrust belts that reveal the shallow structural of the thrusting were constructed.It seems that he frontier of Pamir fold and thrust belts is an arcuate structural belts,which is a surficial nappe overlapping the thrust sheets of the South Tienshan that formed the overlapping relation.The South Tienshan fold and thrust belts mostly have deep-level folding and thrusting.The geographic boundary of South Tienshan and Pamir fold and thrust belts is plotted:in the west it is along Kezilesu River north to the arcuate frontier of Pamir fold and thrust belts,then the north fault of Kelatuo-Minraole anticline belts,finally along the Qiakewukedaliya River that separates the Kelatuo- Minraole anticline belts and Kash anticline belts.(5) After interpreting natural earthquakes since 1953,the author also did a exploratory research on the lithospheric tectonic relationship of South Tienshan orogen,and considered in west and east side,West Kunlun(Xindukushi) orogen and Tafim(Tajike) block,and considered that Tarim(Tajike) block subducts beneath the West Kunlun(Pamir) orogen and South Tienshan orogen in two direction;In Pamir area,a syntaxis formed with the West Kunlun(Pamir) orogen obducts upon the South Tienshan orogen,and result in the two great orogens that rejuvenated during Cenozoic and the subduction and jointing relationship of the two orogens and Tarim(Tajike) block,showing a specific basin-and-range coupling system.更多还原