西藏中部尼雄地区“敌布错组”安山岩夹层的发现及地质意义  

Discovery and geological significance of the andesite intercalation in the“Dibuco Formation”of Nixiong area,central Tibet

作　　者：刘海永 唐菊兴[3] 王雨 唐佐其 张旭东 叶强 曾庆高 孔明明 LIU Haiyong;TANG Juxing;WANG Yu;TANG Zuoqi;ZHANG Xudong;YE Qiang;ZENG Qinggao;KONG Mingming(Tibet Geological Survey,Lasa,Xizang 850000,China;The Second Geological Party,Tibet Bureau of Geological and Mineral Exploration and Development,Lasa,Xizang 850000,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Guizhou Geological Survey,Guiyang,Guizhou 550081,China;Tibet Bureau of Geological and Mineral Exploration and Development,Lasa,Xizang 850000,China;The Six Geological Party,Tibet Bureau of Geological and Mineral Exploration and Development,Lasa,Xizang 850000,China)

机构地区：[1]西藏自治区地质调查院,西藏拉萨850000 [2]西藏地勘局第二地质大队,西藏拉萨850000 [3]中国地质科学院矿产资源研究所,北京100037 [4]贵州省地质调查院,贵州贵阳550081 [5]西藏自治区地质矿产勘查开发局,西藏拉萨850000 [6]西藏地勘局第六地质大队,西藏拉萨850000

出　　处：《地质学报》2024年第6期1701-1714,共14页Acta Geologica Sinica

基　　金：第二次青藏高原综合科学考察专题(编号2019QZKK0702);中国地质调查项目(编号DD20190167、DD20160026)联合资助的成果。

摘　　要：因缺乏高精度年代学制约,尼雄地区“敌布错组”形成时代及地层归属存在争议。本次工作通过对“敌布错组”安山岩夹层进行锆石U-Pb测年,获得~120 Ma的加权平均年龄,结合该区“敌布错组”碎屑锆石研究成果,表明其形成于早白垩世中晚期(130~120Ma),与区域上则弄群火山-沉积地层形成时代一致,建议将其新厘定为则弄群。根据安山岩样品的全岩地球化学及锆石原位Hf同位素组成,认为其是壳源长英质岩浆与幔源玄武质岩浆混合的产物,形成于洋壳俯冲的构造环境。通过进一步对拉萨地体中、新生代岩浆作用的时空变换规律的总结分析,本文研究认为该套安山岩形成的动力学机制主要与新特提斯洋北向俯冲相关。Due to the lack of high-precision chronological constraints,the age and stratigraphic attribution of the“Dibucuo Formation”in Nixiong area are controversial.In this paper,the weighted average age of~120 Ma was obtained through zircon U-Pb dating from the andesite intercalation in the“Dibucuo Formation”.These data,in combination with the existing research data on detrital zircons of the“Dibucuo Formation”in the studied area,led us to conclude that the so-called“Dibucuo Formation”was formed in Early Cretaceous(130~120 Ma),which is consistent with the formation age of the volcanic-sedimentary strata of the Zenong Group in this region.It is thus suggested to tentatively classify the“Dibucuo Formation”into the Zenong Group.According to the whole-rock geochemistry of andesite samples and the in-situ zircon Hf isotopic composition,it is believed that the andesite was derived from the mixture of crustderived felsic magma and mantle-derived basaltic magma,and formed in the subduction tectonic environment.By further summarizing and analyzing the spatio-temporal transformation of Meso-Cenozoic magmatism in the Lhasa terrane,it is revealed that the dynamic mechanism of the formation of this set of andesites is mainly related to the northward subduction of the Neo-Tethys oceanic slab.

关 键 词：青藏高原 尼雄地区 安山岩 岩石成因 构造背景 

分 类 号：P597.3[天文地球—地球化学] P542[天文地球—地质学] P588.144