| 内蒙古西部狼山地区晚古生代变质事件的厘定及其地质意义——来自乌拉山岩群LA-ICP-MS锆石U-Pb定年的新证据 |
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| 引用本文： | 刘平华,邹雷,田忠华,冀磊,施建荣.内蒙古西部狼山地区晚古生代变质事件的厘定及其地质意义——来自乌拉山岩群LA-ICP-MS锆石U-Pb定年的新证据[J].地质通报,2019,38(10):1691-1710. |
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| 作者姓名： | 刘平华 邹雷 田忠华 冀磊 施建荣 |
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| 作者单位： | 中国地质科学院地质研究所, 北京 100037;自然资源部深地动力学重点实验室, 北京 100037,中国地质科学院地质研究所, 北京 100037;自然资源部深地动力学重点实验室, 北京 100037,中国地质科学院地质研究所, 北京 100037;自然资源部深地动力学重点实验室, 北京 100037,中国地质科学院地质研究所, 北京 100037;自然资源部深地动力学重点实验室, 北京 100037,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： | 国家自然科学基金项目《内蒙古西部东阿拉善-狼山前寒武纪变质杂岩多期变质事件》（批准号：41672191）和中国地质调查局项目《华北陆块中部与东部前寒武纪基础地质调查》（编号：DD20190003）、《华北克拉通及周缘关键地质问题调查与变质岩试点填图》（编号：DD20160121） |
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| 摘 要： | 乌拉山岩群是狼山地区最重要的前寒武纪变质基底之一,准确测定其原岩成岩与变质时代,对于进一步探讨狼山地区前寒武纪地质演化具有重要的意义。对狼山地区乌拉山岩群角闪黑云斜长片麻岩及其伴生的花岗质浅色脉体进行了岩石学和锆石U-Pb年代学研究。碎屑锆石U-Pb定年和野外地质调查表明,狼山地区乌拉山岩群角闪黑云斜长片麻岩碎屑锆石年龄介于2591～1800Ma之间,其中最小一组碎屑锆石年龄为1873Ma,结合其约270Ma的变质年龄,初步限定乌拉山岩群角闪黑云斜长片麻岩的原岩沉积年龄为1873～270Ma。综合新的研究资料,认为狼山地区乌拉山岩群除存在新太古代—古元古代变质岩外,可能还存在中元古代—晚古生代变沉积岩。锆石阴极发光图像与U-Pb定年结果综合表明,角闪黑云斜长片麻岩中发育大量变质锆石,获得的206Pb/238U年龄加权平均值为269±4Ma,代表狼山地区乌拉山岩群遭受晚古生代末期角闪岩相变质作用的时代,可能与华北板块与西伯利亚板块晚古生代末期碰撞造山作用有关。此外,采用预剥蚀方法,在乌拉山岩群高硅花岗质浅色脉体高U锆石中,获得的~(206)Pb/~(238)U年龄加权平均值为264±3Ma,被解释为乌拉山岩群花岗质浅色脉体的形成时代,代表本区晚古生代造山作用由同碰撞挤压向碰撞后伸展转换的时限。
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| 关 键 词： | 狼山 乌拉山岩群 晚古生代变质事件 锆石U-Pb定年 |
| 收稿时间： | 2019/5/20 0:00:00 |
| 修稿时间： | 2019/7/5 0:00:00 |
Determination of Late Paleozoic metamorphic event in the Langshan area, western Inner Mongolia: New evidence from LA-ICP-MS zircon U-Pb dating of the Wulashan Group |
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| LIU Pinghu,ZOU Lei,TIAN Zhonghu,JI Lei and SHI Jianrong.Determination of Late Paleozoic metamorphic event in the Langshan area, western Inner Mongolia: New evidence from LA-ICP-MS zircon U-Pb dating of the Wulashan Group[J].Geologcal Bulletin OF China,2019,38(10):1691-1710. |
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| Authors: | LIU Pinghu ZOU Lei TIAN Zhonghu JI Lei and SHI Jianrong |
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| Institution: | Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Beijing 100037, China,Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Beijing 100037, China,Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Beijing 100037, China,Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Beijing 100037, China and Tianjin Center, China Geological Survey, Tianjin 300170, China |
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| Abstract: | Wulashan Group is one of the important parts of the Precambrian basement in the Langshan area, and accurate determination of the diagenetic and metamorphic timing of the Wulashan Group is of great scientific significance for further discussing the Precambrian geological evolution of the Langshan area. In this paper, the authors carried out a detailed study of the petrological observation and zircon U-Pb dating of hornblende biotite plagioclase gneisses and related granitic leucosomes from Wulashan Group. The result of detrital zircon U-Pb dating and geological investigation of the hornblende biotite plagioclase gneisses indicates that the age of detrital zircons of the gneisses of the Wulashan Group in Langshan area ranges from 2591Ma to 1800Ma, and the youngest group age of detrital zircons is circa 1873Ma. Combined with its metamorphic age of circa 270Ma, it is preliminarily considered that the sedimentary age of the gneisses ranges from 1873Ma to 270Ma. The above and latest studies indicate that, besides Neoarchaean-Paleoproterozoic metamorphic rocks, there are also Mesoproterozoic-Late Paleozoic metasedimentary rocks within the Wulashan Group. The result of cathodoluminescence image analysis and U-Pb dating of zircons indicates that a large number of metamorphic zircons exist in the hornblende biotite plagioclase gneisses. They record a 206Pb/238U weighted average age of 269±4Ma, which represents the timing of the late Paleozoic amphibolite-facies metamorphism of the Wulashan Group in the Langshan area, probably in response to the Late Paleozoic collisional orogenesis between the North China Plate and Siberian Plate. In addition, a reliable 206Pb/238U weighted average age of 264±3Ma of the high-U zircons from the high-silica granitic leucosomes was obtained by pre-ablation dating method. The age (264±3Ma) is interpreted as the diagenetic timing of high-silica granitic leucosomes in the Wulashan Group, which represents the timing of the transformation for the collisional extrusion to post-collisional extension during late Paleozoic orogenesis. |
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| Keywords: | Langshan Wulashan Group Late Paleozoic metamorphic event zircon U-Pb dating |
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