西藏洞错地区多尼组砂岩碎屑锆石U-Pb年龄及其地质意义  

Detrital zircon U-Pb age of the Duoni Formation sandstone in Dongcuo area, Tibet,and its geological significance

作　　者：王新录 阿旺旦增 翟杰 索朗旦顿 倪金海 邓加保 蒋孟然 易继尧 WANG Xinlu;AWANG Danzeng;ZHAI Jie;SUOLANG Dandun;NI Jinhai;DENG Jiabao;JIANG Mengran;YI Jiyao(Academy of Regional Geological Survey and Mineral Resources Exploration of Shaanxi,Xianyang 712000,Shaanxi,China;No. 2 Geological Party of Tibet Bureau of Geological Survey,Lhasa 850000,Tibet,China)

机构地区：[1]陕西区域地质矿产研究院,陕西咸阳712000 [2]西藏地勘局第二地质大队,西藏拉萨850000

出　　处：《地质通报》2019年第5期733-741,共9页Geological Bulletin of China

基　　金：中国地质调查局项目《班公湖-怒江成矿带铜多金属矿资源基地调查》(编号:DD20160026)和《西藏改则县洞错南1:5万4幅区域地质调查》(编号:121201103000150004)

摘　　要：对洞错地区早白垩世多尼组砂岩的碎屑锆石进行了U-Pb测年研究。结果表明,锆石颗粒粒径为50~180μm,Th/U值大,约51颗锆石的比值大于0.4,平均值约为0.64,说明锆石大部分为岩浆成因,部分可能为变质成因;锆石年龄主要分布在7个区间范围(或峰值):3261Ma、2739~2335Ma、1880~1750Ma、1006~657Ma、577~510Ma、456~409Ma和252~202Ma。3261Ma的最老碎屑锆石颗粒说明,其物源区存在古太古代古老地壳的残留。锆石U-Pb年龄谱对应羌塘地块经历的几次构造热事件,验证了洞错地区早白垩世沉积物的物源可能来自北部的南羌塘地块。In this paper, the authors conducted some researches on U-Pb geochronology of detrital zircon of the Duoni Formation in Dongcuo area, Tibet. The grain diameter of detrital zircon is 50~180μm. The Th/U ratio is high. The Th/U ratio of 51 zircon samples is greater than 0.4, with the typical value being 0.64. So the magmatic zircon is dominant. The distribution of U-Pb age of zircon is 3261Ma, 2739~2335Ma, 1880~1750Ma, 1006~657Ma, 577~510Ma, 456~409Ma and 252~202Ma. The oldest detrital zircon age is 3261Ma. The provenance of the sediments contained residues of the earth's crust in Archean.The U- Pb age of zircon corresponds to the tectonic event of Qiangtang. So the provenance of Lower Cretaceous Formation in Dongcuo area should be Qiangtang block.

关 键 词：洞错地区 碎屑锆石 物源 多尼组 羌塘地块 

分 类 号：P597.3[天文地球—地球化学] P534.53[天文地球—地质学]