燕山地区团山子组层凝灰岩SHRIMP锆石U-Pb年龄及其地质意义  

SHRIMP zircon U-Pb ages of the tuffite beds in the Tuanshanzi Formation (Changcheng Group) of the Yanshan Mountains, North China Craton

作　　者：马驭舟 苏文博[1] 祝禧艳[2] 刘书琪 李惠民[3] 宋彪[4] MA YuZhou;SU WenBo;ZHU XiYan;LIU ShuQi;LI HuiMin;SONG Biao(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Tianjin Institute of Geology and Mineral Resources,China Geological Survey,Tianjin 300170,China;Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [3]中国地质调查局天津地质调查中心,天津300170 [4]北京离子探针中心,中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2024年第4期1343-1363,共21页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2020YFA0714800);国家自然科学基金项目(41772028、41272046)联合资助。

摘　　要：燕辽地区长城群年代学工作一直是华北克拉通中元古代地质学研究的重点之一。由于团山子组与下伏串岭沟组界限年龄不明确,且此前的年龄都是来自于其中的火山熔岩锆石的年龄,亟待新的测年工作加以验证和完善。本文作者在北京市密云区、平谷区的团山子组下部发现了层凝灰岩,并对其开展了系统的SHRIMP锆石U-Pb测年,获得两个高精度年龄1634±9Ma和1637±8Ma,进一步精确限定了该组的形成年代。结合前人研究,燕辽地区团山子组的底界、也即下伏串岭沟组顶界年龄,可进一步限定为1638Ma。由此可对燕辽地区长城群地层格架进行更准确的年代学厘定,并进一步确认其整体处于持续拉张的裂谷-被动陆缘背景下的快速沉积特征、以及长城群团山子组-大红峪组与华北克拉通南缘汝阳群洛峪口组等相关沉积更为精确的对比关系。结合其他资料还可推断,在团山子组-大红峪组及洛峪口组等形成时,华北克拉通南北两侧都开始被碳酸盐岩浅海覆盖,且最终还可能在其中部出现了南北联通的碳酸盐岩浅海通道。这显示出华北克拉通与早先所拼合克拉通之间已产生明显的拉张性疏离及新生海洋,应标志着华北克拉通从哥伦比亚超大陆裂解的新阶段。The geochronological research of the Mesoproterozoic Changcheng Group, North China Craton (NCC), has been concentrated for several decades. Although lots of significant progress have been achieved in recent years, the exact age of some key horizons and the relevant units, including that of the Tuanshanzi Formation, are still somewhat ambiguous. So far, all the previous chronological studies of the Tuanshanzi Formation have been focused on the zircon U-Pb age dating of the intercalated alkalic volcanic rocks in this formation. However, due to the complicated category of the zircons from the eruptive alkalic rocks, to some extent, it resulted in dispute both about the precise depositional age of the Tuanshanzi Formation and that of the underlying Chuanlinggou Formation, especially while the porphyry dikes and the rapakivi-granite apophysis, truncated by the Changcheng Group in the Yanshan Mountains, have been dated successfully since early 2010's. Hence, further work is needed to verify the exact depositional age of the Tuanshanzi Formation. Recently, some interbedded tuffite beds in the lower part of the Tuanshanzi Formation are firstly recognized in the Miyun and the Pinggu districts, Beijing City, in the Yanshan Mountains. High-precision SHRIMP zircon U-Pb dating yields tuffite ages of 1634±9Ma and 1637±8Ma, and the depositional age of the Tuanshanzi Formation can be calibrated more precisely. Combining with the previous works, the bottom age of the Tuanshanzi Formation, the same with the top age of the underlying Chuanlinggou Formation, can be constrained more tightly as ~1638Ma, and the chronostratigraphic framework of the Changcheng Group in the Yanshan Mountains can be revised, too. This may conform with the characteristic of the rapid depositional setting in this area during the latest Changchengian Period (1650~1600Ma), which should represent a sort of successions from the constantly extending rift-basin to the passive continental margin along the northern NCC. Further, it can lead a more credible strati

关 键 词：SHRIMP锆石U-PB年龄 层凝灰岩 团山子组 长城群 华北克拉通 哥伦比亚(努纳)超大陆 

分 类 号：P317.3[天文地球—固体地球物理学] P597.3[天文地球—地球物理学]