昌宁—孟连带东缘古生界碎屑锆石U-Pb年龄和Hf同位素组成:对原特提斯演化的启示  

The implications of Paleozoic detrital zircon U-Pb age and Hf isotope and Proto-Tethys evolution in the eastern Changning-Menglian belt

作　　者：张斌辉 陆生林 王宏 牛浩斌 陈敏华 Zhang Binhui;Lu Shenglin;Wang Hong;Niu Haobin;Chen Minhua(Chengdu Geological Survey Center of China Geological Survey,Southwest Geological Science and Technology Innovation Center,Chengdu 610213)

机构地区：[1]中国地质调查局成都地质调查中心,西南地质科技创新中心,成都610213

出　　处：《地质科学》2025年第1期150-164,共15页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国地质调查局项目(编号:DD20190053,DD20242111)资助。

摘　　要：临沧地体作为西南三江造山带重要组成单元,其属性和亲缘性还存在较大争议。本文对勐海西定澜沧岩群和石炭系南段组进行了碎屑锆石U-Pb测年和Hf同位素研究。澜沧岩群碎屑锆石有两个年龄主峰:~460 Ma年龄峰(弱负ε_(Hf)(t),约-6.5)与同期惠民弧火山岩相近;~1000 Ma年龄峰(ε_(Hf)(t)=-17.0~+8.7)与格林威尔期锆石相近,最年轻的年龄峰值520~442 Ma。南段组碎屑锆石有两个年龄主峰:600~500 Ma泛非期年龄峰和1.3~1.1 Ga年龄峰,ε_(Hf)(t)变化范围-28.2~+7.81之间。基于最年轻锆石年龄峰值,推测澜沧岩群的沉积时代为早寒武世—奥陶纪。澜沧岩群碎屑锆石年龄谱与思茅地块相似,而南段组碎屑锆石年龄谱则与保山地块相似,推测澜沧岩群的物源来自思茅地块和岩浆弧,而南段组的物源来自冈瓦纳大陆,两者随古特提洋盆闭合才叠置在一起。Lancang Group is a core component of the Lincang terrane,and its age and properties are still highly controversial.U-Pb and Hf isotopic studies of detrital zircons were carried out on five samples from the Lancang Group and two samples from the Nanduan Formation in Xiding area of Menghai.Detrital zircons from the Lancang Group have two main age peaks,the~460 Ma age peak(weakly negative ε_(Hf)(t),~-6.5)is similar to the Huimin arc volcanic rocks,the~1000 Ma age peak(ε_(Hf)(t)=-17.0~+8.7)is similar to the Greenville stage zircons,with the youngest age peaks of 520~442 Ma.The Nanduan Group has two main age peaks,600~500 Ma Pan-African age peak and 1.3~1.1 Ga age peak,with ε_(Hf)(t)varying between-28.2~+7.81.Based on the youngest zircon age peak,the depositional age of the Lancang Group is presumed to be Early Paleozoic.The detrital zircon age spectrum and Hf isotope of the Lancang Group is similar to Simao Block,while the age spectrum of the Nanduan Formation is similar to the Baoshan Block,and there is no inheritance between the Lancang Group and the Nanduan Formation.The source of the Lancang Group is presumed to be the ancient basement and arc volcanic rocks of Simao Block,while the source of Nanduan Group is from the Gondwana,representing the passive continental margin deposition of the Gondwana.

关 键 词：原特提斯 临沧地体 澜沧岩群 南段组 碎屑锆石 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]