【作者】 裴先治；

【导师】 张国伟；

【作者基本信息】 西北大学 ， 构造地质学， 2001， 博士

【摘要】 在现今中国大陆构造中，在中央造山系秦岭一大别造山带的南缘近东西向展布一带分割南北的断裂构造带，即秦岭勉略复合断裂构造带及其东西延展，它是在秦岭造山带中仅次于商丹主缝合带的另一板块碰撞拼合主缝合带基础上，叠加复合中新生代构造所形成的断裂为主的构造带。现今从勉略地区向西经康县、文县、南坪、玛曲、玛沁、花石峡连接东昆南缝合带，向东经巴山弧形构造带而直通大别南缘，是横贯中国大陆的巨型复合断裂构造带，是一条重要的原东古特提斯北侧分支洋盆俯冲消减碰撞缝合带和中国大陆印支期完成其主体拼合的主要结合带。通过构造地质学、岩石学、沉积学和地球化学及地球物理学等多学科综合研究，本文主要对勉略带西延的文县—南坪—玛曲地区和阿尼玛卿山地区的勉略—阿尼玛卿构造带结构、组成和演化进行了综合研究，取得以下主要新进展和初步认识： 1、勉略—阿尼玛卿构造带现今地表构造综合可概括呈现为：近东西—北西西向展布的以自北而南多层次叠瓦状逆冲推覆构造为骨架的巨型向南突出的复合断裂弧形构造带，平面展布上可划分为三个区段：康县—文县—南坪区段、南坪—迭部—玛曲区段、玛曲—玛沁即阿尼玛卿区段。剖面上南坪—文县—康县地区为指向南的多层次逆冲推覆构造系，玛曲—迭部地区南侧则为武都—迭部—玛曲巨型推覆构造，即白龙江构造带的高角度叠瓦式逆冲推覆构造系向南的冲断掩盖截切，而向西则又出露与东部南坪—文县—康县构造相对应的阿尼玛卿地区的指向南的复合逆冲推覆构造系。总体反映了勉略—阿尼玛卿构造带经历长期演化综合而形成的现今构造几何学特点。南坪—文县—康县区段逆冲推覆构造以南部边界东北村—文县—略阳逆冲推覆断裂为主逆冲推覆界面，构成主导自北向南的中高角度逆冲推覆构造系，呈向南突出的弧形展布，可划分为5个构造单元：(1)北缘逆冲推覆构造；(2)桥头—三河口逆冲推覆构造；(3)南坪—黑河逆冲推覆滑脱构造；(4)勉略主缝合带塔藏—石坊—临江—琵琶寺逆冲推覆构造；(5)东北村—勿角—文县—两河口(碧口地块北缘)主边界逆冲推覆构造带。玛曲—南坪间若尔盖地块北缘，由于北侧白龙江逆冲推覆构造带强烈的向南逆冲推覆作用而大量掩覆了从阿尼玛卿区段和康县—文县—南坪区段延伸至此的勉略带的西延部分，原残留的蛇绿岩及相关火山岩系、陆缘沉积岩系等无得以出露，而却使北侧白龙江逆冲推覆构造带在玛曲—带向南呈弧形直接逆冲推覆于若尔盖地块上覆的三叠系之上。西部的阿尼玛卿逆冲推覆构造系具有两种类型构造的复合特征，即(1)主碰撞期叠瓦式逆冲推覆构造系，在剖面上总体表现为自北而南的叠瓦式逆冲推覆构造样式；(2)碰撞后的低角度外来逆冲推覆构造岩片——花石峡—石峡上石炭统—下二叠统厚层灰岩逆冲推覆构造，在平面上和剖面上构成叠加复合的逆冲推覆构造系。 2、通过综合研究和构造解析与不同期次构造的筛分，恢复确定勉略—阿尼玛卿带原为板块缝合带，并将勉略—阿尼玛卿构造带的板块俯冲碰撞构造变形划分为俯冲和碰撞两期变形构造。俯冲阶段的早期变形以大规模低角度自北而南的韧性逆冲剪切变形和较深构造层次的顺层逆冲剪切变形为特征；主造山碰撞早期以近南北向挤压收缩作用形成的同斜褶皱变形为特征，反映了勉略—阿尼玛卿带向北的俯冲消减作用；主造山碰撞晚期以自北向南的逆冲推覆变形为特征，兼有左行走滑作用叠加。在阿尼玛卿地区识别出两种类型的混杂岩，一种是构造变形过程中于俯冲碰撞带形成的由不同时代、不同岩石类型包括蛇绿岩在内构造混杂形成的蛇绿构造混杂岩；另一种是在沉积混杂作用并遭受后期构造变形改造的沉积一构造混杂岩。 3、在阿尼玛卿地区，确定德尔尼蛇绿岩为洋脊型蛇绿岩，发育有具亏损的REE分配模式、EU异常不明显的典型N、MORB，新测定变玄武岩的‘’Ar／’Vr坪年龄为345．3士7．gMa，等时线年龄为336．6士7．IMa，并参考该区所获得的古生物化石依据，表明德尔尼蛇绿岩主要形成于早石炭世。初步确定阿尼玛卿地区存在下大武岛弧型火山岩系、恰格查玛拉岛弧型火山岩系和玛积雪山洋岛型玄武岩系。从构造岩石组合以及地球化学等综合特征表明，阿尼玛卿构造带是一个具有洋脊型蛇绿岩、洋岛型玄武岩和岛弧型火山岩残块等复杂构成的蛇绿构造混杂岩带。在康县一文县一南坪地区，初步确定勉略带上发育有洋岛型玄武岩（OIB）以及N－MORB和 E－MORB型玄武岩，同样代表是洋盆发育的物质记录。琵琶寺玄武岩主要属于板内的拉斑玄武岩，稀士元素分配型式具有两种类型，一是具有亏损的RE E分配模式，EU异常不明显，类似于N＊ORB；二是具有＊M E富集的分配型式，具弱的EU负异常，为洋岛玄武岩，表明琵琶寺玄武岩总体属于洋壳板内洋岛拉斑玄武岩，并有N－MORB型玄武岩。康县地区玄武岩也总体属于洋壳板内洋岛拉斑玄武岩，以洋岛型拉斑玄武岩（OIB）为主，包含有洋岛碱性玄武岩或异常洋脊型玄武岩（E－MOap）。塔藏一隆康一带火山岩主要为中基性火山岩，玄武岩的地球化学特征表明也属于板内洋岛或异常洋脊碱性玄武岩。这些蛇绿岩及火山岩系的发育及性质和特征表明?更多还原

【Abstract】 Qinling Mianlue belt, a composite faulted structure zone, was located in the southern magin of Qinling-Dabie erogenic belt of the Central Orogenic System in China. The belt is another suture zone in the Qinling erogenic belt and a huge structure zone formed faults of superimposition Mesozoic-Cenozoic structure, extending from the East Kunlun belt through Huashixia, Maqen, Maqu, Nanping, Wenxian, Kangxian, and Mianlue area to south magin of Dabie. It is a macroscopic composite faulted structure zone along China continent, an important subduction-collision suture zone of subsidiary ocean basin of north side in Eastern Paleo-Tethys, representing main site of Indosinian welding of North China Block with Yangtze Block. This thesis mainly focus on structure, composition and evolution of the Mianlue-A’nyemaqen zone in Wenxian-Nanping-Maqu region and A’nyemaqen region with comprehensive research of the structure geology, petrology, sedimentology, geochemistry and geophysics, by which some new points are achived,1. Mianlue-A’nyemaqen zone presently was preserved as an EW to NWW-striking gigantic multi-layerd overthursting faulted zone in southward arcuating, which can be divided into Kangxian-Wenxian-Nanping Sections, Nanping-Diebu-Maqu Section and Maqu-Maqen Section (also termed as A’nyemaqen belt). The Kangxian-Wenxian-Nanping Section represents a southward multi-layered overthrusting faulted structural system. The Diebu-Maqu Section is overlapped in the South by the Bailongjiang steep-angle overthrusting system but crop out in the west as composite overthursting zone comparable in structure with the west counterpart. The major thrusting interface of the Kangxian-Wenxian-Nanping overthursting system is the Dongbeicun-Wenxian-Lueyang fault, making up a southward mid-to-steep angle arcuate thursting system, which can be 5 structural elements, 1) northern magin overthrusting structure; 2)Qiaotou-sanhekou overthrusting structure; 3)Nanping-Heihe overthrust-decollement structure; 4) major suturing zone, presently represented as Tazang-Wenxian-Linjiang-Pipasi overthrusting structure belt; 5)major overthrusting zone at the northern margin of Bikou Block. In Maqu-Nanping area and the northern part of Rergai Block, as the overlapping of Bailongjiang thrust nappe over the Triassic sediment of Rergai Block, possible relic Ophiolite and related igneous rocks are locally absent. The A’nyemaqen overthrusting system in the west displays 2 characteristics, 1) syn-collisional southwards imbricated overthrusting structure; 2) post-collisional low-angle allochthonous thrusted slices, exampled by C3-P] block limestone thursted nappe near Huashixia-Shixia, which construct overlapped composite thrust system in both horizontal and vertical sections.2. The Mianlue-A’nyemaqen belt is proven to be a tectonic suturing zone, where deformation can be divided into 2 stages corresponding to the subducting and collision, respectively. The deformation in early stage of subducting is characterized by southwards low-angle ductile shearing and lower-depth horizontal shearing thrust. Deformation in Early stage of collision is characterized by N-W compressnal isoclinal folds, representing northwards subducting in the Mianlue-A’nyemaqen belt. In later collisional stage is featured by southwards overthrust and laevorotatory shearing. Two type of melange are recognized in A’nyemaqenarea, one of which is ophiolitic melange formed by tectonic jumbling associated with subduction and collision of rocks in different origins and ages, another type is associated with sedimentary processes and experienced later deformative modifications.3. The Dur’ngoi Ophiolite is recognized from A’nyemaqen area, which yields typical depleted REE pattern and 40Ar/39Ar plateau age of 345.3h7.9Ma, with an isochronal age of 336.d;7.1Ma. Together with fossils discovered in this area, the formation age of Dur’ngoi Ophiolite is constrained within early Carboniferous period. Regional investigations provide preliminary recognitions of oceanic island basalt (OIB)更多还原