【作者】 李康；

【导师】 陈汉林；

【作者基本信息】 浙江大学 ， 构造地质学， 2014， 博士

【摘要】 帕米尔弧形构造带的弧形扩展机制、南天山与帕米尔的对接过程现今学者仍存在不少争论。帕米尔弧形构造带的形成是通过径向逆冲、走滑断裂还是撕裂断层调节?南天山与帕米尔的对接过程是什么样的,其构造与沉积格架如何?为解决这些问题,本文选择帕米尔东北缘为研究区,得出以下认识和结论：1.帕米尔东北缘晚新生代的构造变形特征与空间演化差异。通过野外剖面结合地震解释的方法,完成了乌泊尔、苏盖特—英吉沙、齐姆根、普西四个构造带的典型地震剖面解释和空间展布差异性特征分析。认为帕米尔东北缘构造以压扭和走滑为特点。压扭应力下形成喀什—叶城转换系统、羊大曼走滑断裂等右旋走滑断层与一系列雁列式展布的背斜带,如英吉沙背斜、艾古斯背斜等。齐姆根和普西构造带以走滑构造形成的半花状构造为特征。2.帕米尔东北缘晚新生代沉积特征及对构造的约束。通过对奥依塔格、同由路克两个野外剖面的实测,结合钻井资料等,建立了区域晚新生代地层各组的对比柱状图。结合本文采样的5个野外剖面与4口钻井的重矿物分析,利用聚类分析、重矿物组合对比、重矿物交汇指数图解等方法进行物源研究。通过野外剖面与柱状图对比认为巴什布拉克组、阿图什组和西域组沿着造山带走向岩性变化不大,但乌恰群安居安组表现出强烈的岩性差异,在和什拉甫—阿尔塔什一线为冲积扇相砾岩,而在其他剖面以湖相泥岩为主。和什拉甫附近的冲积扇相砾岩具有构造指示意义,本文认为这与中新世走滑活动启动是吻合的,重矿物分析也表明和什拉甫附近中新世不稳定重矿物增多。但在全区尺度上,重矿物不稳定成分的增多主要在阿图什组和西域组中,反映了阿图什组沉积之后构造变形迅速向北楔入。另外沿着造山带走向,重矿物种类和含量反应了物源源区性质(北帕米尔火成岩含量居多,西昆仑变质岩含量居多)。3.通过对乌泊尔背驮盆地地貌特征、地震地层解释、残余厚度图编制等手段,试图约束帕米尔与南天山对接过程。本文认为乌泊尔背驮盆地的启动是三大断裂体系(帕米尔北缘断裂与主帕米尔逆冲断裂、乌泊尔深部盲断裂)脉冲式活动的产物,盆地的沉积中心迁移主要受控于这些断裂的相对活动强度,另外整体上存在沉积中心自西向东的扩展趋势。这种自西向东的扩展趋势在地貌高程、水系展布上也有响应。通过对阿莱盆地和乌泊尔背驮盆地的平衡剖面恢复,将帕米尔和南天山的对接过程细化为两个时期：第一阶段为帕米尔北缘断裂的持续向北楔入,在阿莱盆地晚渐新世—早中新世开始启动,在乌泊尔背驮盆地中新世晚期开始启动；第二阶段在阿莱盆地中新世中期开始启动,以后缘断裂活动形成前陆型盆地为特征,在乌泊尔背驮盆地于上新世开始启动,以前缘断裂活动形成背驮型盆地为特征。4.通过本文的构造与沉积特征工作,结合GPS速度场、古地磁等数据,对帕米尔东北缘弧形扩展模式的三种端元模型(径向逆冲、右旋走滑、撕裂断层模型)进行了评估。认为三种模型均有合理和不合理的一部分,但在某一个时期内,某一种端元模型占主导地位。因此,本文提出了帕米尔东北缘的弧形扩展模式在不同阶段以不同模型主导：渐新世时期以径向逆冲模型为主,主要来自于古地磁数据的支持；中新世时期以走滑模型为主,证据来自于本文的构造与沉积工作；上新世以来变形前锋大规模楔入塔西南盆地,构造带间以撕裂断层模型调节为主。证据来自于本文的构造、沉积工作与现今GPS速度场数据。这种三个不同阶段以三种不同模型主导的混合模型,需要区域应力场发生过两次重大转变。本文认为这两次构造转换事件与喀什—叶城走滑系统的启动,以及帕米尔和南天山完全对接事件相关。更多还原

【Abstract】 Debates about the kinematics of the Pamir salient exist as the first-order structural and sedimentary features of the NE Pamir is rarely understood. Three end-member models are proposed and discussed in this dissertation:radial-thrusting model, dextral strike-slip model and tear fault model. We analysis different structural sytles responded to the three models, combining with the structural and sedimentary characteristics of the NE Pamir. Following conclusions can be made by the research of this dissertation:1. Field mapping combining with seismic interpretation contours the basic strcutrual frame of the region, which is dominated by transpressoinal stress and dextral strike-slip. Dextral Kashi-Ycheng Transfer System, Yangdaman Fault affect the formation of several en-echolon folds systems, such as Yingjisha Anticline, Qibei nose structure, etc. The Qimugen and Puxi area are featured by strike-slip-related half flower structure.2. Sedimentary works, including stratigraphic section description at Oytage and Tongyouluke Section, and comprisons among sedimentary columns throughout the region, establish the basic sedimentary characteristics of the NE Pamir. The Bashibulake Formation, Artux Formation and Xiyu Formation don’t change much along the strike of the orogen. However, the Anjuan Formation in the Wuqia Group, shows strong lithofacies variations. Along the Heshilafu-Aertashi belt, the Anjuan Formation is characterized by alluvial conglomarates. While in other region, the Anjuan Formation is featured by lacustrine mudstone. Heavy mineral analysis reconfirm this lithofacies variations. Along the Heshilafu Section and nearby regions, unstable heavy minerals appears in the Anjuan Formation. However, the unstable heavy minerals commonly appear after the deposition of the Artux Formation, which may indicate the intense northward-indention into the Tarim Basin since the Pleiocene. The variety and the contents of the havy minerals also indicate the along-strike changes of the provenance lithology, where the Pamir is dominated by igneous rocks, but the West Kunlun is mostly metamorphic rocks.3.The Wupoer Piggyback Basin lies close to the collision zone between the Pamir and the Tian Shan, thus archives the progressively process of the collision. Geomorphological, drainage system, seismic interpretation and isopach maps are analysised to understand the collision process. The depocenter loci are controlled by the relative motion of the Main Pamir Thrust, Pamir Frontal Thrust, and Wupoer Blind Thrust between them. Additionally, a west-to-east trend of deformation is proposed as the depocenter and balanced cross-section indicated the chonological order difference between the Alai Basin and the Wupoer Piggyback Basin.4. We consider three end-member types both exist in the evolution of the NE Pamir, but they developed in different stages:a) In the Oligocene, radial-thrusting exist both along the west and the east flank of the Pamir, clockwise rotation took place in the NE Pamir which is indicated by paleomagnetic datas. b) In the Miocene, cextral transfer faults KYTS accommodate the variant displacements of the NE Pamir salient, which is supportted by our structural and sedimentary analysis, c) From the Pleiocene to the present, deformation along the MPT and the KYTS is inactive and frontal structures indented northward into the Tarim Basin. Tear faults systems exist between fold-and-thrust belts to accommodate the different displaments of these zones. Swithes in the three models indicate tectonic activities or stress field changes in the Early Miocene and the Early Pleiocene. We interpret these changes are related to the onset and weaken of the KTYS, and the fully collision between the Pamir and Tian Shan.更多还原