| 青藏高原羌塘中部不同时代榴辉岩的识别及其意义——来自榴辉岩及其围岩~（40）Ar-~（39）Ar年代学的证据 |
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| 引用本文： | 张修政,董永胜,李才,陈文,施建荣,张彦,王生云.青藏高原羌塘中部不同时代榴辉岩的识别及其意义——来自榴辉岩及其围岩~（40）Ar-~（39）Ar年代学的证据[J].中国区域地质,2010(12):1815-1824. |
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| 作者姓名： | 张修政 董永胜 李才 陈文 施建荣 张彦 王生云 |
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| 作者单位： | [1]吉林大学青藏高原研究中心,吉林长春130061 [2]中国地质科学院地质研究所氩-氩同位素年代学实验室,北京100037 |
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| 基金项目： | 国家自然科学基金项目（编号：40872146、40672147）; 中国地质调查局项目（基[2010]矿评02-03-07）资助 |
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| 摘 要： | 羌塘中部高压变质带由榴辉岩、石榴子石白云母片岩、蓝片岩等组成,与蛇绿混杂岩、晚古生代浅变质地层岩片等共同构成了龙木错-双湖板块缝合带这一构造混杂岩带。目前已先后在片石山地区、果干加年山地区和冈玛错地区发现典型的榴辉岩,以片石山和果干加年山地区的榴辉岩为研究对象。片石山地区的榴辉岩为低温型榴辉岩,围岩为石榴子石白云母片岩,变质作用峰期温压条件为T=500℃,p=2.3GPa。已获得230～244Ma锆石SHRIMP U-Pb年龄和石榴子石Lu-Hf等时线年龄,代表榴辉岩相变质作用的时代。榴辉岩及其围岩在误差范围内具有相同的Ar-Ar年龄,为210～220Ma,代表了榴辉岩及其围岩冷却抬升至近地表的时代。果干加年山地区的榴辉岩具有和片山地区榴辉岩相似的野外产状、矿物组合、温压条件和围岩。Ar-Ar年代学研究显示,果干加年山地区的榴辉岩在240Ma左右即已折返并抬升至近地表,其变质作用峰期时代明显要早于片石山地区。
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| 关 键 词： | 羌塘中部 榴辉岩 石榴子石白云母片岩 40Ar-39Ar测年 俯冲消减 |
Identification of the eclogites with different ages and their tectonic significance in central Qiangtang,Tibetan Plateau： Constraints from ~（40）Ar-~（39）Ar geochronology. |
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| ZHANG Xiu-zheng,DONG Yong-sheng,LI Cai,CHEN Wen,SHI Jian-rong,ZHANG yan,WANG Sheng-yun.Identification of the eclogites with different ages and their tectonic significance in central Qiangtang,Tibetan Plateau： Constraints from ~（40）Ar-~（39）Ar geochronology.[J].Regional Geology of China,2010(12):1815-1824. |
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| Authors: | ZHANG Xiu-zheng DONG Yong-sheng LI Cai CHEN Wen SHI Jian-rong ZHANG yan WANG Sheng-yun |
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| Institution: | 1.Research Center For Tibetan Plateau,Jilin University,Changchun 130061,Jilin,China; 2.Laboratory of Isotope Geochronology,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China |
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| Abstract: | The high pressure metamorphic belt in central Qiangtang consists of eclogite,glaucophane schist and garnet-muscovite schist.It constitutes part of Longmucuo-Shuanghu-Lancang river plate suture zone,together with Late Paleozoic epirock and ophiolite melange.Recently,eclogites have been found in Pianshishan area,Guoganjianianshan area and Gangmacuo area in turn.In this paper,we focus on the eclogites in Pianshishan and Guoganjianianshan area.The Pianshishan eclogites enclosed within garnet-muscovite schist have peak metamorphic p-T conditions at T=500℃ and p=2.3GPa.The ages ranging between 230 and 244Ma are given by U-Pb dating of zircons and Lu-Hf datings,and were interpreted as the peak metamorphic age of eclogites.Ar-Ar datings of eclogites and their country rocks gave similar ages ranging between 210Ma and 220Ma,representing the cooling age of the eclogites during retrograde metamorphism.On the other hand,the Guoganjianianshan eclogites have similar field occurrence,mineral assemblage,p-T conditions and country rocks to those of Pianshishan eclogites.However,Ar-Ar datings show that the peak metamorphic age of the Guoganjianianshan eclogites obviously differ from that of Pianshishan eclogite.These data suggested that the Guoganjianianshan eclogites had been exhumated to shallow crust lever at about 240Ma. |
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| Keywords: | central Qiangtang eclogite garnet-muscovite schist 40Ar-39Ar age subduction |
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