滇中易门地区古元古界易门群罗洼垤组火山岩锆石U-Pb年龄及其构造热事件  

Zircon U-Pb age and tectonic thermal event of the volcanic rocks from the Paleoproterozoic Yimen Group Luowadie Formation in Yimen area,Central Yunnan

作　　者：刘军平 宛胜 李静 邓仁宏 赵江泰 陈棵 吴嘉林 LIU Junping;WAN Sheng;LI Jing;DENG Renhong;ZHAO Jiangtai;CHEN Ke;WU Jialin(Yunnan Institute of Geological Survey,Kunming 650216,Yunnan,China;School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,MNR,Kunming 650051,Yunnan,China;Geological Survey of Jiangxi Province,Nanchang 330000,Jiangxi,China)

机构地区：[1]云南省地质调查院,云南昆明650216 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]自然资源部三江成矿作用及资源勘查利用重点实验室,云南昆明650051 [4]江西省地质调查院,江西南昌330000

出　　处：《地质通报》2021年第7期1024-1032,共9页Geological Bulletin of China

基　　金：中国地质调查局项目《全国陆域及海区地质图件更新与共享》子项目《云南省系列地质图件数据处理与洋板块地质研究》(编号:DD20190370) 、《云南 1∶5 万二街、易门、鸣矣河、上浦贝幅区域地质调查》(编号:DD20160017);云南省国土资源厅基金项目《云南省1:5万撒马基幅、因民幅、贵城幅、舒姑幅区域地质调查》(编号:D201905)

摘　　要：易门群是综合了元江撮科、易门铜厂、东川因民等地区的最新野外地质资料、同位素年代学资料后厘定的古元古界浅变质地层。其记录了地球发展演化早期的一系列重大地质事件,如古元古代早期的休伦冰期事件及紧随其后的地幔柱事件、简单多细胞生物的首现、狭义的Lomagundi碳同位素正漂移事件、富氧大气崩溃后的缺氧富硒沉积等。采用锆石激光剥蚀法(LA-ICP-MS)对易门地区的易门群罗洼垤组微晶凝灰岩、英安质凝灰岩进行了年龄测定,获得锆石U-Pb年龄加权平均值为2241±16 Ma、2252±14 Ma,2件样品的锆石Th/U值为0.2~1.0,均具清晰的振荡环带结构,为岩浆成因的锆石。结果表明,滇中易门地区罗洼垤组沉积时代为古元古代中期,可与元江撮科的地幔柱岩石构造组合及东川因民的罗洼垤组凝灰岩的时代对比。罗洼垤组沉积时代可能是Kenorland超大陆裂解作用在扬子陆块的响应。Yimen Group is the Palaeoproterozoic weakly metamorphic strata determined by the latest“Yunnan Province Regional Geology”(second edition of revision)project,which integrates the latest field geological data and isotope chronology data of Yuanjiang Cuoke,Yimen Tongchang and Dongchuan Yinmin.It records a series of major geological events in the early stages of the Earth's evolution,such as the Early Paleoproterozoic Huron Ice Age event and the following mantle plume events,the first appearance of simple multicellular organisms,the narrow Lomagundi carbon isotope positive drift event,and hypoxic selenium-rich deposits after the collapse of oxygen-rich atmosphere.The LA-ICP-MS zircon dating method was used to date the Luowadie microcrystalline tuff and the dacite tuff in the Yimen Group of Yimen area.The zircon U-Pb dating yielded a weighted average age of 2241±16 Ma(MSWD=0.64,n=14),2252±14 Ma(MSWD=0.71,n=13).The zircon Th/U ratio of the two samples is 0.2~1.0,both of which have a clear oscillating ring structure,indicating the zircon of magmatic origin.The study indicates that the sedimentary time of the Luowadie Formation in the Yimen area of the Yime area is Middle Paleoproterozoic,which can be compared with the mantle plume tectonic combination of the Yuanjiang Couke and the tuff in the Luowadie Formation of Dongchuan Yinmin.The sedimentary time of the Luowadie Formation may represent the response of Kenorland supercontinent splitting in Yangtze.

关 键 词：古元古界易门群 锆石U-PB年龄 滇中易门地区 Kenorland超大陆 

分 类 号：P534.3[天文地球—古生物学与地层学] P597.3[天文地球—地质学]