| 北阿尔金恰什坎萨依沟地区早古生代构造变形特征及构造演化启示 |
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| 引用本文： | 吴玉,陈正乐,陈柏林,王永,孟令通,孙岳,何江涛,王斌,张文高. 北阿尔金恰什坎萨依沟地区早古生代构造变形特征及构造演化启示[J]. 地质力学学报, 2019, 25(3): 301-312. DOI: 10.12090/j.issn.1006-6616.2019.25.03.028 |
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| 作者姓名： | 吴玉 陈正乐 陈柏林 王永 孟令通 孙岳 何江涛 王斌 张文高 |
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| 作者单位： | 核工业北京地质研究院地质矿产研究所, 北京100029;中国地质科学院地质力学研究所, 北京100081;中国地质科学院地质力学研究所动力成岩成矿实验室, 北京100081;中国地质科学院地质力学研究所, 北京100081;中国地质科学院地质力学研究所动力成岩成矿实验室, 北京100081;东华理工大学, 江西 南昌330013;中国地质科学院地质力学研究所, 北京100081;中国地质科学院地质力学研究所动力成岩成矿实验室, 北京100081;中国科学院地质与地球物理研究所,北京,100029;东华理工大学,江西 南昌,330013;中国地质调查局天津地质调查中心,天津,300170 |
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| 基金项目： | 国家自然科学基金（41802218）;"十二五"国家科技支撑计划项目（2011BAB06B08-04）;中国核工业地质局铀矿地质科研项目（地D1902） |
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| 摘 要： | 出露在青藏高原北缘的红柳沟-拉配泉蛇绿混杂岩带一直以来为深入研究北阿尔金早古生代构造格架及演化提供了宝贵信息。经详细的野外地质填图和构造解析,文章针对红柳沟-拉配泉蛇绿混杂岩带内的构造样式、变形特征及形成时限进行研究,将北阿尔金蛇绿混杂岩带进一步细分为北侧混杂单元、中间层序单元和南侧混杂单元三个次级构造单元,南、北两侧混杂单元内以发育一系列复杂褶皱和逆冲断层为典型构造特征。卷入褶皱变形的最年轻地层岩石为中-晚奥陶世硅质岩,并被（416.8±3.7）Ma未变形的正长斑岩脉所截切;卷入逆冲断层的混杂岩中辉长岩和斜长花岗岩年龄为479~521 Ma和512.1~518.5 Ma,随后也被410.7~418.5 Ma未变形的冰沟岩体所侵位。这些基本事实表明,褶皱构造与逆冲断层均形成于中奥陶世-早泥盆世,推测其成因与北阿尔金洋俯冲作用导致的洋壳强烈缩短变形有关。在南侧混杂单元,褶皱构造样式自北向南逐渐由直立褶皱转变为斜歪褶皱,最后转变为倒转褶皱,显示出递进变形特征。褶皱所对应的应变椭球体也发生了旋转,表现出顶端指向北北东向的剪切作用,与混杂单元内逆冲断层所具有的向北北东方向逆冲、推覆特征相一致,从而推测它们与北阿尔金洋南南西向俯冲消减有密切联系。另外,在北侧混杂单元内还发育有同时期向南南东方向逆冲的断层以及轴面倾向北北东的斜歪褶皱,暗示北阿尔金洋在早古生代可能还发育有北北东方向的俯冲极性,整个北阿尔金洋俯冲消减模式可能具有双向性。
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| 关 键 词： | 混杂岩 褶皱 逆冲断层 构造演化 早古生代 北阿尔金 |
| 收稿时间： | 2018-12-26 |
| 修稿时间： | 2019-04-10 |
EARLY PALEOZOIC TECTONIC DEFORMATION IN QIASHENKANSAYIGOU AREA, NORTH ALTUN, AND IMPLICATION FOR TECTONIC EVOLUTION |
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| WU Yu,CHEN Zhengle,CHEN Bailin,WANG Yong,MENG Lingtong,SUN Yue,HE Jiangtao,WANG Bin and ZHANG Wengao. EARLY PALEOZOIC TECTONIC DEFORMATION IN QIASHENKANSAYIGOU AREA, NORTH ALTUN, AND IMPLICATION FOR TECTONIC EVOLUTION[J]. Journal of Geomechanics, 2019, 25(3): 301-312. DOI: 10.12090/j.issn.1006-6616.2019.25.03.028 |
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| Authors: | WU Yu CHEN Zhengle CHEN Bailin WANG Yong MENG Lingtong SUN Yue HE Jiangtao WANG Bin ZHANG Wengao |
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| Affiliation: | 1.Beijing Research Institute of Uranium Geology, CNNC, Beijing 100029, China2.Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China3.The Laboratory of Dynamic Digenesis and Metallogenesis, Institute of Geomechanics, CAGS, Beijing 100081, China4.East China Institute of Technology, Nanchang 330013, Jiangxi, China5.Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China6.Tianjin Center, China Geological Survey, Tianjin 300170, China |
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| Abstract: | Hongliugou-Lapeiquan ophiolitic mélange belt, which is exposed in the northern margin of the Qinghai-Tibet Plateau, has been providing significant information for the deep study of Early Paleozoic tectonic framework and evolution of North Altun. On the basis of detailed geological mapping and structural analysis, ophiolitic mélange belt was divided into the following three sub-tectonic units from north to south:the north incoherent unit, the middle coherent unit and the south incoherent unit. There mainly develop a series of complex folds and thrust faults in the north and south incoherent units. The youngest stratum involved in the folds is formerly defined Middle-Late Ordovician silicalite. SHRIMP zircon U-Pb dating from a Syenite porphyry dyke, truncating the above folds, yielded a weighted mean age of 416.8±3.7 Ma. The gabbro and plagiogranite in the mélange are involved in the thrust fault and have U-Pb age of ca. 479~521 Ma and ca. 512.1~518.5 Ma, respectively. Meanwhile, one undeformed Bingou pluton intruding the thrust fault was dated at ca. 410.7~418.5 Ma. All of these results support that the age of the folds and thrust faults in the incoherent units are tightly constrained at the Middle Ordovician to early Devonian, implying that the deformation in the ophiolitic mélange are related to an intense compression during the subduction of the North Altyn ocean. In the south incoherent unit, the characteristics of folds, from north to south, developed from upright fold to reclined fold to overturned fold, revealing a progressive deformation assemblage associated with the top-to-the-NNE shearing. Combined with top-to-the-NNE thrust fault in the south incoherent unit, it is indicated that these folds and thrust faults are as the product of the SSW-ward subduction of the North Altun ocean. In addition, folds with axial surface dipping to NNE and top-to-the-SSE thrust faults are common in the north incoherent unit, implying that the North Altun ocean has also experienced NNE-ward subduction during the Early Paleozoic. Thus, it is proposed that the North Altun ocean is characterized by divergent double subduction. |
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| Keywords: | mélange fold thrust fault tectonic evolution Early Paleozoic North Altun |
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