【作者】 孙桂华；

【导师】 李锦轶；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2007， 博士

【摘要】 了解造山带的构造变形特点,是研究造山带形成演化过程的一项重要内容,也是获得造山带运动学和动力学信息的主要途径之一。从板块演化角度看,造山带可以划分为俯冲型造山带和碰撞型造山带。哈尔里克山位于新疆东部,吐哈盆地东北缘,天山山脉东北部,构造位置上处于准噶尔造山系与天山造山系的交汇部位,古生代期间长期属于板块俯冲带的上盘,是开展俯冲型造山带构造变形研究,了解俯冲型造山带地壳形成演化的理想地区。作者在该区做硕士学位论文发现,哈尔里克山南麓小铺一带变质岩的变质、变形年龄为290Ma左右,属于前人提出的“塔里木盆地以北的新疆北部地区320～280Ma为后碰撞演化”阶段时限范围,当时获得的构造变形资料,并不支持前人关于其运动学特征及动力学机制的认识。显然,该区尚需详细的变形构造研究。本文选择新疆东部哈尔里克山为研究对象,通过详细的野外路线地质构造调查和关键地区大比例尺地质填图,以及室内显微结构观察、石英岩组分析和构造热年代学(Ar-Ar和锆石SHRIMP U-Pb定年)研究,结合前人研究成果,取得了如下新进展:1、系统重建了哈尔里克山晚古生代以来的变形历史识别和确定了该区板块俯冲碰撞阶段的二叠纪以前挤压变形,后碰撞阶段早二叠世伸展变形、中二叠世近东西向右行走滑变形和晚二叠世近南北向挤压变形,以及板内演化阶段的晚新生代南北向挤压变形等5期构造变形事件。根据Ar-Ar热年代学研究,精确测定了早二叠世伸展变形和晚二叠世挤压变形的峰期时代分别为290Ma和259Ma。2、提出了关于哈尔里克山南麓小铺一带变质带和变质作用的新认识根据显微观察资料和特征变质矿物的出现,把小铺一带的变质岩由SW向NE方向依次划分为黑云母带、石榴石带、十字石带、红柱石带和矽线石带等变质带;初步确定该区的变质作用属于中温-低压型,变质作用发生的时代为290Ma左右,是该区早二叠世地壳伸展的产物。3、首次提出哈尔里克山南麓在石炭纪可能发育弧后盆地的新观点根据哈尔里克山南麓原“居里得能组”岩屑砂岩的碎屑锆石SHRIMP U-Pb定年,确认这套地层的沉积不早于晚泥盆世,很可能是石炭纪,而不是前人所说的前寒武纪;结合对其区域地质背景、源区位置和沉积环境分析,推测该区石炭纪可能为滞后弧后盆地和弧后隆起区构造背景。4、进一步证明哈尔里克山不发育与岛弧演化相关的泥盆纪岩浆活动根据对代表性闪长岩和花岗岩的锆石SHRIMP年代学研究获得的新资料,结合该区已有相关资料的综合研究,确定哈尔里克山岩浆岩分别形成于奥陶纪-志留纪和石炭纪晚期-二叠纪,不存在泥盆纪的岩浆岩,进而认为该区泥盆纪不属于岛弧环境。5、重建了哈尔里克山古生代以来的地质演化过程根据区域资料以及本次研究所获得的资料,把哈尔里克山古生代以来的构造演化划分中奥陶世-早志留世为岛弧、中志留世-晚泥盆世为弧后区、石炭纪弧后伸展、二叠纪为后碰撞伸展与挤压、中生代差异隆升和晚新生代陆内再造山过程等构造阶段。6、初步估算了哈尔里克山地壳缩短率和缩短量根据前中生代地层褶皱估算的哈尔里克山南山口-口门子、石城子-白石头和沁城-小铺三条剖面的地壳缩短率分别为16.2%、19.8%和20.1%,相应的地壳缩短量分别为4.3km、9km和11.3km。这一结果表明哈尔里克山晚古生代期间的地壳缩短量表现出由西向东逐渐增强的变化趋势。7、初步总结了俯冲型造山带地壳演化的主要特点以哈尔里克山为代表的俯冲型造山带的构造演化,经历了洋盆收缩阶段的弧后扩张、洋盆关闭阶段的陆(弧)-陆碰撞、后碰撞阶段的伸展与挤压以及板内阶段的挤压等几个演化阶段,其中的碰撞-后碰撞阶段和板内阶段的演化,与碰撞型造山带构造演化没有明显区别。更多还原

【Abstract】 Being one major content of orogenic evolution, study of deformation history is an effective way to reveal the kinematics and/then discuss the dynamic process of the orogen. In the view of the plate-evolution, orogen is commonly divided into two types: subduction and collision ones. Being the northeastern segment of the Tianshan orogen, the Harlik range is located at the northeastern margin of the Tu-Ha basin, east Xinjiang, NW China. In the view of tectonics, the Harlik Mountain is situated at the junction area of the Junggar orogenic system and Tienshan orogenic system, which had been belong to the overriding plate of a subduction zone during the entire Paleozoic period. Thus, the Harlik range provides an excellent natural laboratory for studying the deformation features and crust growth of a subduction-type orogen.During working in this area for my master degree, I found that the deformation -metamorphism age of the Xiaopu metamorphic rocks is ca. 290 Ma, exactly bracketing within the age scope of 320 to 280 Ma, which was though as the post-collision stage in the north Xinjiang (north of the Tarim basin). However, my structural observations did not provide kinematic pattern to support such a tectonic model. Obviously, further kinematic analyses are required to solve this contradiction.Here I reported new structural data to answer above question, including field section observations and geologic map with large scale in a key area, accompanying with detail microstructural observations, quartz C-axial fabric analyses, and tectono-thermogeochronology (40Ar/39Ar and zircon SHRIMP U-Pb method). Taking available previous data into account, following progression is achieved:1. Completely rebuilding the post late-Paleozoic deformation history of the Harlik MountainFive stages of deformation were identified: (1)pre-Permian compression deformation which may have resulted from pre-Permian subduction; (2) earlier Permian post-collision extension; (3) middle Permian west-east directed dextral slip shearing; (4) later Permian nearly N-S compression deformation; and (5) later Cenozoic intra-plate N-S compressional deformation. Of the five stages deformation, the exact ages of the (2) and (3) were determined by 40Ar/39Ar method as 290 and 259 Ma respectively.2. New results on the metamorphic belts and associated metamorphism of the Xiaopu metamorphic rocksBased on detailed microtextural observations and occurrence of typical metamorphic minerals, five metamorphic belts in the Xiaopu metamorphic rocks are identified. From the north to the south, they are biotite belt, garnet belt, staurolite belt, andalusite belt, and sillimanite belt. I suggested that the metamorphic belts occurred in the Xiaopu area belongs to the high temperature/low pressure (HT/LP) series, may have resulted from the later Permian crust extension at ca. 290 Ma.3. I suggest that there may have been a Carboniferous backarc basin along the southern slope of the Harlik Mountain.Detrital Zircon SHRIMP U-Pb dating indicated that the sedimentary age of the Julideneng formation lithic sandstone must be later than late Devonian, most likely is Carboniferous rather than previously thought Precambrian. Analyses on its geologic setting, location of provenance, and sedimentary environment suggest the Carboniferous strata may form in a lagged backarc basin bounded by backarc uplifts.5. Reconstruction of the post-Paleozoic tectonic evolution history of the Harlik MountainThe tectonic evolution of Harlik mountains since the Paleozoic were reconstructed as followings: (1) arc-affinity magmative activities occurred during the middle-Ordovician to early-Silurian; (2) the middle-Silurian to late-Devonian was a back-arc uplift stage; (3) back-arc extension featured the Carboniferous period; (4) post-collisional extension and/then compression during Permian; (5) at the Mesozoic, differential uplift developed; and (6) the late Cenozoic is the intra-continental re-orogen stage.6. Primary estimation of the crust shortening is madeThe folded pre-Mesozoic strata were used to estimate crust shortening along the Harliknanshankou-Koumenzi, Shichengzi-Baishitou, and Qincheng-Xiaopu sections. Their shortening ratios are 16.2%, 19.8%, and 20.1% respectively corresponding crust shortening are 4.3, 9, and 11.3 km. These results suggest a clear eastward increasing in the late Paleozoic crust shortening of the Harlik Mountain.7. Primary summary of the crust growth feature of the subduction-type orogenBeing a subduction-type orogenic belt, the Harlik mountains experienced several stages of tectonic evolution, including back-arc spreading during contraction of oceanic basin, continent-continent or arc-continent collision after oceanic closure, post-collision extension and compression, and intra-plate compression. No obvious difference exists between the later two stages tectonic evolution and that of a collisional orogenic belt更多还原