中条山岩墙群的时代及其对华北1.8 Ga大火成岩省事件性质的制约  

Age of the Zhongtiaoshan dyke swarm:Constraints on the nature of the 1.8 Ga large igneous province event in North China

作　　者：袁玲玲 王祎帆[1] 张晓晖 Lingling Yuan;Yifan Wang;Xiaohui Zhang(Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education,School of Geoscience and Info-Physics,Central South University,Changsha 410083,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中南大学地球科学与信息物理学院,有色金属成矿预测与地质环境监测教育部重点实验室,长沙410083 [2]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [3]中国科学院地球科学研究院,北京100029

出　　处：《科学通报》2023年第21期2824-2835,共12页Chinese Science Bulletin

基　　金：国家自然科学基金(41903030)资助。

摘　　要：中条山地区发育大量弱变质或未变质的中基性岩墙,它们是华北克拉通中元古代初期(1.80~1.76 Ga)大规模岩墙群的重要组成部分,准确厘定其侵位时代对构建岩墙群的精细时-空分布规律,以及认识华北克拉通该时期地球动力学过程有重要意义.此次研究对永济王庄村附近的一条近东西向岩墙开展了斜锆石离子探针定年,获得其^(207)Pb/^(206)Pb年龄为1799±4 Ma(n=20,MSWD=2.2).该年龄有效填补了关键地区岩墙群的时代空缺,为揭示华北中元古代初期复合岩墙群中熊耳(1800~1785 Ma)和太行(1770~1760 Ma)两个不同世代岩墙群的形成时代和空间分布特征提供了重要线索.同时,中条山1799 Ma中基性岩墙也是目前报道的华北克拉通最早的未变质岩墙,作为熊耳期岩浆活动可能的开端,它不仅为限定熊耳群火山岩系底界年龄提供了重要参考,也为以大火成岩省(或岩墙群)为标志的地体对比和超大陆重建提供了新的依据.综合岩墙群的几何学、年代学和地球化学特征,本文支持熊耳、太行岩墙群是地幔柱在不同阶段作用于运动的华北克拉通大陆板块岩石圈的产物.The geodynamic regimes that led to the formation of the early Mesoproterozoic (1.80–1.76 Ga) large-scale mafic dyke swarm in the North China Craton (NCC) have long been controversial.One school of scholars insisted their preference for post-collisional lithospheric extension related to amalgamation of the Eastern and Western blocks,while others argue for a mantle plume-triggered intracontinental rift setting.This owns much to the failure to characterize the refined temporalspatial distribution of the dyke swarm.In the Zhongtiaoshan area,numerous low-grade metamorphosed to unmetamorphosed intermediate-mafic dykes constitute an important portion of the southern segment of this giant dyke swarm.Nevertheless,precise chronological constraints for their emplacement timing are still lacking.Given the superiorities of the baddeleyite U-Pb isotope system in dating silica-undersaturated igneous rocks,we plan to determine the formation age of dykes in the southern Zhongtiao Mountain by in-situ Pb/Pb dating of baddeleyites using an ion microprobe.Combined with a brief introduction to the field geologic and geochemical characteristics of the Zhongtiaoshan dykes,this paper is intended to provide new clues to understanding the deep dynamic process of magmatism represented by the dyke swarm.We sampled an EW-trending dyke near Wangzhuang Village in Yongji City.A baddeleyite~(207)Pb/~(206)Pb dating for this sample yields a magmatic crystallization age of 1799±4 Ma (n=20,MSWD=2.2).This result effectively fills the vacancy of dyke ages in the key area,and reinforces the view that the early Mesoproterozoic complex dyke swarm comprises two stages of dykes,namely,the Xiong’er (1800–1785 Ma) and Taihang (1770–1760 Ma) dyke swarms,which are exposed in the middle-southern portion of the central NCC and throughout the central NCC,respectively.Meanwhile,we also analyzed the whole-rock elemental and Nd isotopic compositions of the Yongji dyke from the Zhongtiaoshan area.It reveals that the trace element distribution patterns and the

关 键 词：华北克拉通 中元古代初期 岩墙群 中条山 熊耳地幔柱 

分 类 号：P588.1[天文地球—岩石学] P534.3[天文地球—地质学]