【作者】 赵朋；

【导师】 闵伟；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2009， 硕士

【摘要】 青藏高原东北缘属柴达木—祁连活动地块,是青藏高原向大陆内部扩展的前缘部位,也是其最新的和正在形成的重要组成部分。该地块晚新生代到现今的构造变形十分强烈,遍布全区的晚第四纪活动逆冲断裂、走滑断裂和活动褶皱表明整个地区正在遭受地壳缩短和左旋剪切作用。阿尔金断裂带为青藏块体西北缘一条大型北东东向左旋走滑断裂,由多条次级断裂组成,全长约1600km,具逆冲—左旋走滑特性。习惯上将阿尔金断裂分为西、中、东三段,其中东段在阿克塞以东,断裂的左旋滑动速率沿走向向东规则递减,与其东部段落上肃北、石包城和疏勒河等3个三联点想南东扩展的活动逆断层上盘推覆体逆冲抬升密切相关。肃北是西边的第一个三联点,该地区位于祁连山褶皱带西南缘,柴达木盆地和祁连山之间,区内构造复杂。对于该地区的研究主要集中在阿尔金断裂肃北段,而对于肃北以东地区的研究比较薄弱,基本处于空白。肃北地区有4条主要断裂:野马河北侧断裂、野马河南侧断裂、肃北西南逆冲断裂以及党河南山断裂,另外还有3个断裂作用控制的小型盆地:肃北盆地、野马河盆地和盐池湾盆地。根据本地区的研究现状,对以下内容进行调查和研究:1)区域地貌特征及其与构造的关系,包括水系、山脊、盆地、冲洪积扇的分布特点,构造活动对地形地貌的影响等。2)区域内重要断裂,即野马河南侧断裂、野马河北侧断裂、肃北西南逆冲断裂以及党河南山逆断裂。通过实地勘察,追踪这些断裂带的空间展布和断裂地质地貌特征,收集分析相关资料,揭示断裂晚第四纪活动性。3)通过对区域内断裂晚第四纪活动特征的研究,结合学者对该地区其他断裂的研究成果,区域内主要断裂构造的运动特征和转换关系。通过野外调查及室内分析,结合已有资料,得出的主要结论:1)野马河北侧断裂总体走向70°,长约30km。以老虎沟为界可以分为东、西两个几何不连续段,两者呈左阶排列。该断裂是一条左旋走滑兼逆冲活动断裂,逆冲活动以北盘向南盘逆冲为主,控制了野马河盆地的西北缘。野马河北侧断裂是一条晚第四纪以来比较活跃的断裂,晚更新世以来的平均逆冲速率为(0.4±0.07)mm/a,平均水平滑动速率为(1.27±0.18)mm/a。2)野马河南侧断裂东西向展布,总全长约65km。该断裂东西两侧出露于地表的部分均具有明显的逆冲、走滑地质地貌特征,控制了野马河盆地的南缘。野马河南侧断裂是一条晚更新世以来比较活跃的断裂。其中,西段全新世以来的平均滑动速率为:5.65±0.51mm/a,逆冲速率为0.25±0.03mm/a。东段全新世以来的平均左旋滑动速率:0.28±0.07mm/a,全新世以来的平均逆冲速率为0.11±0.02mm/a。断裂东段开挖的探槽揭示该断层发生过2次古地震事件。3)肃北西南逆断裂整体呈反“S”形,总体走向NWW,长约17km。沿断裂发育了较多典型的逆冲推覆地貌,以及冲沟出露的断层剖面,叠瓦状逆冲断层比较发育,控制了肃北盆地的西南缘。肃北西南逆冲断裂是一条典型的逆冲断裂,晚更新世晚期以来的平均逆冲速率为0.86±0.16mm/a;水平活动速率相对较弱。4)党河南山逆断裂是展布于党河南山北侧前缘地带,总体走向NW。断裂以逆冲为主,南盘向北逆冲,错断了全新世洪积扇,控制了盐池湾盆地的西南缘。该断裂晚更新世晚期以来的平均逆冲速率为0.04±0mm/a。北侧断裂开挖的探槽揭示该断裂发生过1次古地震事件,南侧断裂开挖的探槽揭示该断裂发生过3次古地震事件。在肃北地区,阿尔金断裂东段运动量的减少,被三部分构造运动所分解,一是野马河北侧断裂和野马河南侧断裂以左旋走滑、逆冲的形式所分解;二是党河南山的隆升和党河南山逆断层所引起的地壳缩短所分解,三是肃北地区的其他构造,如盆地、褶皱的活动所分解。总的来看,肃北地区的主要断裂滑动速率和逆冲速率都比较低,叠瓦状逆冲现象比较普遍,区内有断裂、盆地、褶皱等多种构造参与了变形分解和运动转化,这些结论都说明了该地区物质向东挤出的速率和幅度是有限的,符合“叠瓦状逆冲转换—有限挤出模型”。更多还原

【Abstract】 Northeastern margin of Qingzang Plateau is Qaidam - Qilian block, is the extension of the Qingzang Plateau to the leading edge of the mainland partand also the newest and important part of the formation. From Late Cenozoic to the current, the tectonic deformation of this block is very intense.The activities of the Late Quaternary thrust fault, strike-slip fault and active folding indicats that the whole region is suffering from crustal shortening and sinistral shearing. Altyn Tagh fault for the northwest edge of Qingzang block is a large north east left spin strike-slip faults which is composed of multiple second-order faults, is approximately 1600km long, and has thrust -left-lateral strike-slip characteristics .Generally, Altyn Tagh fault is divided into western,middle and eastern three sections.The eastern section is in the east of Akesai, the fractured left-slip rate descends along the east, and is relevant to the active reverse upfaulted thrust lifting of triple junction with Subei、Shibaocheng and Shule River of the eastern section .Subei is the first triple point of the west side, the region is located in the southwestern margin of Qilian fold belt, between the Qaidam Basin and Qilian Mountains,and the inside structure of the region is complex. For research in the area mainly concentrated in the Altun fault Subei fragment, while for the study of the area to the east Subei is relatively weak,basically in the blank. Four main faults in Subei: Yemahe-northern fault, the Yemahe-southern fault, the Subei-southwest thrust fault and Danghenanshan thrust fault,in addition, three faulting small-scale basin: Subeibasin, Yemahe basin and Yanchiwan basin. According to the currunt situation of research in the region, to carry out an investigation of the following contents :1) The relationship of regional tectonic features and textrue includes the distribution characteristics of water, ridges, basins, alluvial-proluvial fan, and the influence of tectonic activity to topography and landform.2) The important faults in the region are the Yemahe-northern fault, the Yemahe-southern fault, the Subei-southwest thrust fault and Danghenanshan thrust fault. Through field investigation, to keep track of the spatial distribution of fault and the geological features of these faults, to collect and analyze relevant information and revealthe late Quaternary fault activity.3) Through the study of the intraregional faults late Quaternary activity characteristic, and in combination with the research results of scholars in the other faults in this region, and the movement characteristics of intraregional main fault and conversion relations.Through field investigation and indoor analysis, combined with the existing data, the main conclusions:1) The Yemahe-northern fault r totally trends to 70°,is about 30km,which can be divided into East and West two geometric discontinuous paragraphs and the two paragraphs left-orderly array. The fault is a sinistral strike-slip and thrust active fault, the active faul mainly thrut up from the northern plate to the southern plate south to control the the north-west edge of Yemahe River Basin.T Yemahe-northern fault was a active fault since the Late Quaternary, the average rate of thrust was (0.4±0.07) mm / a, the average slip rate was (1.27±0.18) mm / a in the Late Pleistocene epoch.2) the Yemahe-southern fault spreads from east to west, with a total length of approximately 65km. The east and west sides of the faults exposed at the surface clearly thrust, has strike-slip geomorphology features and control the southern margin of the Yemahe River Basin.the Yemahe-southern fault was a more active fault since the Late Pleistocene. The average slip rate of the western part in the Holocene was 5.65±0.51mm / a,the thrust rate was 0.25±0.03mm / a. The sinistral average rate of the eastern section was 0.28±0.07mm / a,the thrust average rate was 0.11±0.02mm / a since the Holocene. The costean of eastern section revealed that the fault has the twice ancient seismic events.3) the Subei-southwest thrust fault overall was the anti-reverse "S" shape, the overall trend NWW, with the length ot approximately 17km.Along with the fracture,developed the more typical thrust topography, as well as exposed the fault profile, and the imbricate thrust was more development to control the southwestern margin of the Subei basin.the Subei-southwest thrust fault was a typical thrust fault, the thrust average rate was 0.86±0.16mm / a;the level of activity rate was relatively weak since the late Pleistocene.4) Danghenanshan thrust fault developed to the frontalzone of Dang-he-nan-shan mountain north side,whose overall trend was NW. Thrust fault was mainly reverse thrust,the south tray was northward thrust, wrong cut off the Holocene alluvial fan,and controlled the southwestern margin of the Yanchiwan basin. Since late Pleistocene , the averager reverse rate of the thrust fault was 0.04±0mm / a. The costean of northern section revealed that the fault has the twice ancient seismic events, the costean of the southern fault revealed that the fault has three times ancient seismic events.In Subei region, the decrease in the amount of exercise of the eastern section of the Altyn Tagh fault was decomposed three-part by tectonic movement, the reason was that:first, the Yemahe-northern fault and the Yemahe-southern fault was decomposd in the form of sinistral strike-slip and reverse thrust;second,the decomposition of the crustal shortening was caused by the up lifting and the thrust fault of Danghenanshan mountain;third,other structure in Subei areas,such as the decomposition of the activities of baisins and flod.Overall, the slip and reverse thrust rate of the main fracture of Subei is lower, the phenomenon of thrust-imbricated is relatively common, there are faults, basins, folds and other structures involved in the deformation and movement transform.These conclusions suggest that the extrusion rate and extent to east of the material is limited, in line with the "thrust imbricated conversion - limited extrusion model."更多还原