北京大学学报自然科学版 ›› 2024, Vol. 60 ›› Issue (2): 210-226.DOI: 10.13209/j.0479-8023.2023.098

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五台地区高凡群沉积年代、物源性质与构造环境

白璐, 关平, 呼其图, 宋丹丹   

  1. 造山带与地壳演化教育部重点实验室, 北京大学地球与空间科学学院, 北京 100871
  • 收稿日期:2023-03-25 修回日期:2023-09-11 出版日期:2024-03-20 发布日期:2024-03-20
  • 通讯作者: 关平, E-mail: pguanl(at)pku.edu.cn
  • 基金资助:
    国家重点研发计划(2021YFA0719000)和国家自然科学基金(42141021)资助

Depositional Age, Provenance Characteristics and Tectonic Setting of Gaofan Group in the Wutai Area

BAI Lu, GUAN Ping, HU Qitu, SONG Dandan   

  1. The Key Laboratory of Orogenic Belts and Crustal Evolution (MOE), School of Earth and Space Sciences, Peking University, Beijing 100871
  • Received:2023-03-25 Revised:2023-09-11 Online:2024-03-20 Published:2024-03-20
  • Contact: GUAN Ping, E-mail: pguanl(at)pku.edu.cn

摘要:

针对山西五台地区高凡群的沉积年代、物源类型和沉积构造环境等研究中有争议的问题, 选择山西忻州市代县滩上镇出露的高凡群经典剖面进行系统采样以及详细的沉积学和岩石学分析, 并挑选典型样品进行全岩矿物组成、锆石U-Pb定年以及主量和微量元素的测定。通过碎屑锆石U-Pb定年, 并综合前人发表的年龄数据, 确认高凡群的沉积时代为约2.2 Ga, 与下伏五台群及上覆地层滹沱群之间为上下叠置关系。高凡群沉积岩的主量和微量元素组成指示其源岩类型主要为中酸性岩浆岩, 表明在高凡群沉积时期大陆上地壳以花岗岩类为主。碎屑中锆石年龄分布和细粒沉积岩中全岩主量和微量元素的构造判别图解表明, 高凡群具有活动大陆边缘的特征。然而, 沉积学分析显示高凡群形成于被动大陆边缘的滨浅海相。这种矛盾的结论, 或许暗示不能用根据板块构造理论衍生出的构造判别方法来研究古元古代时期的沉积构造背景。

关键词: 五台地区, 高凡群, U-Pb年龄, 物源, 构造背景

Abstract:

Addressing the debated aspects of the study on the depositional age, provenance, and sedimentary tectonic environment of Gaofan Group in the Wutai area of Shanxi, systematic sampling and detailed sedimentological and petrological analysis were conducted on the classic section of Gaofan Group exposed in Tanshang Town, Daixian County, Xinzhou City, Shanxi Province. Typical samples were selected for whole rock mineral composition, zircon U-Pb dating, major and trace element determinations. By analyzing detrital zircons and synthesizing previously published age data, the depositional age of Gaofan Group was considered to be approximate 2.2 Ga. This chronologic analysis showed that Gaofan Group was in a superposition relationship with the underlying Wutai Group and overlying Hutuo Group. The major and trace element composition of Gaofan Group indicated that the source rock was mainly intermediate-acidic igneous rock, suggesting that during the deposition of Gaofan Group, the upper continental crust was predominantly composed of granitoids. The age distribution of detrital zircons and tectonic discrimination diagrams based on major and trace elements of fine-grained sedimentary rocks suggested that Gaofan Group exhibited characteristics of an active continental margin. However, sedimentological analyses indicated that it was deposited in a passive continental margin with littoral and neritic facies. This contradictory conclusion may suggest that the tectonic discrimination methods derived from plate tectonic theory may not be applicable for studying the sedimentary tectonic background during the Paleoproterozoic period.

Key words: Wutai area, Gaofan Group, U-Pb dating, provenance, tectonic background