| 甘肃敦煌东巴兔山地区敦煌杂岩的变质 变形特征及时代限定 |
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| 引用本文： | 刁志鹏,朱文斌,吴海林.甘肃敦煌东巴兔山地区敦煌杂岩的变质 变形特征及时代限定[J].高校地质学报,2019,25(1):144. |
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| 作者姓名： | 刁志鹏 朱文斌 吴海林 |
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| 作者单位： | 内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京210023;内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京210023;内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京210023 |
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| 基金项目： | 国家重点研发计划;国家重点研发计划;国家自然科学基金;国家自然科学基金;中国地调局项目 |
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| 摘 要： | 敦煌地块位于塔里木克拉通的东南缘，是塔里木克拉通前寒武纪岩石出露的重要地区之一。敦煌地块包括北阿尔金
地区和敦煌地区，区域内出露的最古老岩石分别被称为米兰杂岩和敦煌杂岩，文章研究重点是敦煌地区出露的敦煌杂岩。
敦煌杂岩由TTG质片麻岩和变质表壳岩组成，代表性岩石组合包括英云闪长质片麻岩、奥长花岗质片麻岩、花岗闪长质片
麻岩、石榴石斜长角闪岩、石榴石黑云母片岩以及大理岩。文章对东巴兔山干沟地区的花岗闪长质片麻岩样品进行了
LA-ICP-MS锆石U-Pb测年，对石榴石黑云母片岩样品进行了矿物电子探针分析，同时对敦煌杂岩开展了构造变形研究，目
的是揭示敦煌杂岩的形成时代、构造变形特征以及变质温压条件。花岗闪长质片麻岩样品的结晶年龄为2057±75 Ma，并且
记录了~1.88 Ga和~400 Ma两期变质作用，分别与古元古代和古生代的造山事件相关。构造变形研究表明敦煌杂岩记录了两
期变形作用，分别为区域上的右形韧性剪切作用（S1） 和南北向褶皱作用（S2），且右形韧性剪切作用（S1） 和~400 Ma的变
质作用是配套同期的。此外，对石榴石黑云母片岩样品的分析表明，~400 Ma这期变质作用变质峰期的矿物组合主要为石
榴石+黑云母+斜长石+石英，且变质温压条件为667~690 ℃/0.88~0.89 GPa，代表了高角闪岩相的变质作用。
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| 关 键 词： | 敦煌杂岩 古元古代 构造变形 变质温压 碰撞造山 |
Metamorphism,Deformation and Chronological Constraints on the Dunhuang Complex in Dongbatu Area,Dunhuang, Gansu Province |
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| DIAO Zhipeng,ZHU Wenbin,WUHailin.Metamorphism,Deformation and Chronological Constraints on the Dunhuang Complex in Dongbatu Area,Dunhuang, Gansu Province[J].Geological Journal of China Universities,2019,25(1):144. |
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| Authors: | DIAO Zhipeng ZHU Wenbin WUHailin |
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| Abstract: | The Dunhuang block is located at the southeastern margin of the Tarim Craton and is an important region where the
Precambrian rocks are exposed. The Dunhuang block includes the northern Altyn Tagh and the Dunhuang regions. The oldest rocks
exposed in both regions are known as the Milan complex and the Dunhuang complex respectively. While, the focus of this study is the
Dunhuang complex. TTG gneisses and metamorphic supracrustal rocks make up the Dunhuang complex mainly, and the dominant
rocks are composed of tonalitic gneiss, trondhjemitic gneiss, granodioritic gneiss, garnet amphibolite, garnet biotite schist and marble.
In this study, LA-ICP-MS U-Pb dating was performed on the zircons of granodioritic gneiss sample from the Gangou area and the
sample of garnet biotite schist was analyzed by electron probe, moreover, the structural deformation of the Dunhuang complex was
studied in order to reveal the geochronology, characteristics of structural deformation and P-T conditions of metamorphism of the
Dunhuang complex. We report that the crystallization age of the granodioritic gneiss sample was 2057±75 Ma. and also Two episodes of
metamorphism were recorded, the older one has the age of ~1.88 Ga representing the Palaeoproterozoic orogeny, whereas the younger
one with the age of ~400 Ma may relate to the Paleozoic orogenic event. The study of structural deformation has shown that the
Dunhuang complex underwent two episodes of deformation, namely the right-lateral ductile shearing (S1) and S-N-trending folding (S2),
and the right-lateral ductile shearing (S1) occurred at the same period of the ~400 Ma metamorphism. In addition, analysis of the garnet
biotite schist sample revealed that the metamorphic peak mineral assemblages of the ~400 Ma metamorphism were mainly composed of
garnet, biotite, plagioclase and quartz, and that the temperature and pressure conditions of metamorphism during the peak are 667~
690 ℃/0.88~0.89 GPa, which represent the high-temperature amphibolite-facies metamorphism. |
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| Keywords: | words：Dunhuang complex Paleoproterozoic structural deformation P-T conditions of metamorphism collisional orogenesis |
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