| 勉略构造带新元古代中期构造演化特征:来自略阳关天门变质沉积岩碎屑锆石U-Pb年代学和地球化学的证据 |
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| 引用本文： | 王昭阳,裴先治,李瑞保,裴磊,李佐臣,刘成军,赵少伟,王盟,陈有炘,周海,赵杰,许丽丽.勉略构造带新元古代中期构造演化特征:来自略阳关天门变质沉积岩碎屑锆石U-Pb年代学和地球化学的证据[J].现代地质,2022,36(3):770-795. |
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| 作者姓名： | 王昭阳 裴先治 李瑞保 裴磊 李佐臣 刘成军 赵少伟 王盟 陈有炘 周海 赵杰 许丽丽 |
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| 作者单位： | 1.长安大学 地球科学与资源学院,陕西 西安 7100542.西部矿产资源与地质工程教育部重点实验室,陕西 西安 710054 |
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| 基金项目： | 国家自然科学基金项目(41872233,41872235,41802234,41902046)；;陕西省自然科学基金项目(2020JQ-353,2019JM-312)；;中央高校基本科研业务费资助项目(300102270202,300102270107,300102279108)； |
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| 摘 要： | 秦岭南缘勉略构造带略阳关天门地区发育有一套绿片岩相-低角闪岩相岩石组合,是勉略构造带内强烈韧性变形的变质沉积岩系,其形成时代和构造属性长期存在争议,制约区域大地构造演化的研究。为查明其形成时代与构造背景,对其中的变质细碎屑岩进行系统的岩石学、碎屑锆石U-Pb年代学和岩石地球化学研究。2件碎屑锆石U-Pb年龄样品的年龄分布特征相似,主要年龄区间为新元古代早中期(ca.880~800 Ma),并且显示出ca.830 Ma的显著峰值;最年轻的一组碎屑锆石年龄为747~736 Ma(平均年龄742±6 Ma)。地球化学研究结果表明,关天门变沉积岩原岩应为一套细碎屑岩偶夹碳酸盐岩的沉积组合,原岩经历了较低程度的化学风化和沉积物再旋回,其物源主要为大陆岛弧背景下的中-酸性岩浆岩。结合区域已有研究成果,认为关天门变沉积岩的物源主要为碧口微地块、汉南—米仓山微地块的新元古代早中期岩浆弧。通过野外地质调查,并与已有的区域碎屑锆石年龄谱系进行对比,认为关天门变沉积岩岩片的沉积时代应晚于碧口微地块横丹群形成的时间(720 Ma),即关天门变沉积岩岩片的沉积时限应晚于720 Ma,形成于新元古代中期伸展裂陷体制,是Rodinia超大陆裂解过程的响应。
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| 关 键 词： | 勉略构造带 变沉积岩 岩石地球化学 LA-ICP-MS锆石U-Pb定年 南华系 |
| 收稿时间： | 2021-06-09 |
| 修稿时间： | 2022-04-10 |
Middle Neoproterozoic Tectonic Evolution of the Mianlue Tectonic Belt: Evidences from Detrital Zircon U-Pb Geochronology and Geochemistry of the Guantianmen Metasedimentary Rocks in Lueyang County |
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| WANG Zhaoyang,PEI Xianzhi,LI Ruibao,PEI Lei,LI Zuochen,LIU Chengjun,ZHAO Shaowei,WANG Meng,CHEN Youxin,ZHOU Hai,ZHAO Jie,XU Lili.Middle Neoproterozoic Tectonic Evolution of the Mianlue Tectonic Belt: Evidences from Detrital Zircon U-Pb Geochronology and Geochemistry of the Guantianmen Metasedimentary Rocks in Lueyang County[J].Geoscience——Journal of Graduate School,China University of Geosciences,2022,36(3):770-795. |
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| Authors: | WANG Zhaoyang PEI Xianzhi LI Ruibao PEI Lei LI Zuochen LIU Chengjun ZHAO Shaowei WANG Meng CHEN Youxin ZHOU Hai ZHAO Jie XU Lili |
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| Institution: | 1. School of Earth Science and Resources, Chang’an University, Xi’an,Shaanxi 710054, China2. Key Laboratory of Western Mineral Resource and Geological Engineering of Ministry of Education, Xi’an,Shaanxi 710054, China |
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| Abstract: | A suite of greenschist to lower-amphibolite-facies metasedimentary rocks is exposed at Guantianmen in the Mianlue tectonic belt, and is characterized by intense ductile deformation. The depositional ages and tectonic settings of these rocks have long been controversial, which limits our understanding on the regional tectonic evolution. To constrain their depositional ages and tectonic settings, we conducted petrology, petrogeochemistry, and LA-ICP-MS detrital zircon U-Pb dating on the metasedimentary rocks. The results show that protoliths of the Guantianmen metasedimentary rocks are a set of fine-grained clastic rocks with local carbonate interbeds. Our work indicates that the metasedimentary rocks have undergone low-degree chemical weathering and sedimentary recycling, and were mainly derived from felsic to intermediate igneous rocks with continental arc signature. Two samples yielded similar age distributions, displaying a dominant ca.880-800 Ma age group with a main age peak at ca.830 Ma. The youngest age group is 747-736 Ma(avg.742±6 Ma). Combined with previous work, we suggest that the main provenance region of the Guantianmen metasedimentary rocks is the Early-Middle Neopro-terozoic magmatic arc in the Bikou and Hannan-Micangshan microblocks. The depositional age of the Guantianmen metasedimentary rocks should be later than 720 Ma. The rocks were most likely deposited in an extensional rift system during the middle-Late Neoproterozoic, in response to the Rodinia supercontinent breakup. |
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| Keywords: | Mianlue tectonic zone metasedimentary rock petrogeochemistry LA-ICP-MS zircon U-Pb da-ting Nanhua system |
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