| 北阿尔金地区古元古代岩体LA-ICP-MS锆石U-Pb年龄及其地质意义 |
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| 引用本文： | 王斌,王永,陈柏林,陈正乐,吴玉,孟令通,何江涛,王玉刚,韩梅梅,祁万修,刘兵,赵雷.北阿尔金地区古元古代岩体LA-ICP-MS锆石U-Pb年龄及其地质意义[J].地质通报,2017,36(6):964-976. |
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| 作者姓名： | 王斌 王永 陈柏林 陈正乐 吴玉 孟令通 何江涛 王玉刚 韩梅梅 祁万修 刘兵 赵雷 |
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| 作者单位： | 1. 中国地质大学 (北京) 地球科学与资源学院, 北京 100083;2. 中国地质科学院地质力学研究所, 北京 100081;3. 新疆地质矿产勘查开发局第一区域地质调查大队, 新疆 乌鲁木齐 830013 |
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| 基金项目： | 国家自然科学基金项目《阿尔金北缘早古生代造山型金矿床构造-流体成矿过程》（批准号：41502086） |
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| 摘 要： | 北阿尔金是塔里木克拉通变质基底的主要出露区之一。对该区具有侵入接触关系的正长花岗岩和花岗片麻岩进行了LA-ICP-MS锆石U-Pb定年研究。正长花岗岩中的锆石多呈椭圆状,具有振荡环带结构,部分颗粒中可见老锆石残核,Th/U值较高,亏损轻稀土元素,富集重稀土元素,具有负Eu异常和正Ce异常的特点,表明该组锆石为岩浆成因。定年结果获得1903±13Ma和2506±55Ma两组年龄加权平均值,前者代表岩体的结晶年龄,后者为捕获锆石年龄,结合区域年代学资料,认为正长花岗岩岩浆侵入过程中可能捕获了太古宇米兰群的古老基底锆石。花岗片麻岩中16个测点的锆石~(207)Pb/~(206)Pb年龄集中于1802±28Ma,代表了岩体侵位时代,其余5个测点的锆石~(207)Pb/~(206)Pb年龄为1911~1951Ma,说明岩浆侵位过程中捕获了部分正长花岗岩的物质。区域地质与同位素年代学研究表明,北阿尔金地区广泛存在2.0~1.8Ga的构造-热事件。获得的花岗质岩石的1.9~1.8Ga的年龄结果,直接证实了北阿尔金存在约1.9Ga的岩浆作用,可能为古元古代Columbia超大陆汇聚事件在该地区的响应,为探讨塔里木板块前寒武纪构造-热事件演化历史提供了新资料。古元古代末期约1.8Ga的花岗片麻岩,代表了后造山伸展阶段的岩浆活动。
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| 收稿时间： | 2016/6/9 0:00:00 |
| 修稿时间： | 2017/1/7 0:00:00 |
LA-ICP-MS zircon U-Pb dating of Paleoproterozoic pluton in northern Altun area and its geological implications |
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| WANG Bin,WANG Yong,CHEN Bailin,CHEN Zhengle,WU Yu,MENG Lingtong,HE Jiangtao,WANG Yugang,HAN Meimei,QI Wanxiu,LIU Bing and ZHAO Lei.LA-ICP-MS zircon U-Pb dating of Paleoproterozoic pluton in northern Altun area and its geological implications[J].Geologcal Bulletin OF China,2017,36(6):964-976. |
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| Authors: | WANG Bin WANG Yong CHEN Bailin CHEN Zhengle WU Yu MENG Lingtong HE Jiangtao WANG Yugang HAN Meimei QI Wanxiu LIU Bing and ZHAO Lei |
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| Institution: | 1. School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;3. No.1 Regional Geological Survey Party, Xinjiang Bureau of Geology and Mineral Exploration and Development, Urumqi 830013, Xinjiang, China |
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| Abstract: | North Altun region is one of the main regions where the metamorphic basement of the Tarim craton is exposed.In this pa-per, LA-ICP-MS U-Pb dating was conducted on zircon grains from syenogranite and granitic gneiss that have intrusive contact rela-tionship with each other.Most zircons from the syenogranite are characterized by oval shape, typical oscillatory zoning, and residual cores in some grains.The higher Th/U ratios, depletion of LREE and enrichment of HREE, an obvious negative Eu anomaly, and positive Ce anomaly indicate that they are of magmatic origin.The dating results yielded two age groups of weighted mean ages of 1903±13 Ma and 2506±55 Ma.The former age represents the crystallization age of the intrusions, and the latter one represents the age of inherited zircon.Combined with available regional chronologic data, the authors hold that ancient basement zircons of Archean Milan Group may have been involved in the process of granite magma intrusion.Most analyzed spots are clustered around 1802±28 Ma, which represent the crystallization age of the granitic gneiss.The other five analyzed spots yielded 207Pb/206Pb ages of 1911~1951 Ma, implying that part of the granite material was captured in the process of magmatic emplacement.The existing regional geo-logical and isotopic chronologic data suggest that northern Altun region may exist 2.0~1.8 Ga tectonic thermal events.So the crystalli-zation age of granitic rocks 1.9~1.8 Ga directly confirms the existence of the magmatism at 1.9 Ga, such a tectonic magmatic event is consistent with the global collisional orogeny events related to the evolution of Columbia supercontinent, and this can provide new evidence for the exploration of Precambrian tectonic thermal event and its evolution history along the Altun tectonic belt.The forma-tion of granitic gneiss in Late Paleoproterozoic at 1802±28 Ma may represent the post-orogenic stage in North Altun region. |
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| Keywords: | northern Altun region LA-ICP-MS zircon U-Pb dating Paleoproterozoic tectonic thermal event |
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