念青唐古拉花岗岩的同位素年龄测定及其地质意义  

Isotopic Dating of the Nyainqentanglha Granite and Its Significance

作　　者：刘琦胜[1] 吴珍汉[1] 叶培盛[1] 胡道功[1] 江万[1] 柯东昂 张汉成[3] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]河北省区域矿产地质调查研究所,廊坊065000 [3]中国地质大学,北京100083

出　　处：《地质学报》2005年第3期331-337,共7页Acta Geologica Sinica

基　　金：国家重点基础研究项目(编号2002CB412600);西藏当雄幅1:25万区域地质调查项目(编号H45C002001)资助成果

摘　　要：念青唐古拉花岗岩体位于西藏当雄县境内,是拉萨地块中部出露的巨型侵入岩岩基,其面积超过1500km2,以大面积出露的黑云母二长花岗岩为主体。本文分别应用单矿物K-Ar法、全岩-单矿物Rb-Sr等时线法和高灵敏度高分辨率离子探针法(SHRIMP-)对念青唐古拉岩体不同位置上的代表性岩石样品进行同位素测年,得到中细粒黑云母二长花岗岩的K-Ar年龄为8.49±0.14Ma,Rb-Sr等时线年龄为8.07±0.35Ma和8.70±1.40Ma,SHRIMPU-Pb年龄为18.3±0.4Ma;中粗粒黑云母二长花岗岩的K-Ar年龄为9.80±0.35Ma,Rb-Sr等时线年龄为9.33±0.41Ma,SHRIMPU-Pb年龄为11.01±0.24Ma。不同方法测年结果均表明念青唐古拉花岗岩形成于中新世,属拉萨地块内部最年轻的巨型花岗岩岩基,其侵位结晶时代处于青藏高原地壳由南北向挤压增厚向东西向伸展的转变时期,岩浆来源于地壳局部熔融,属后碰撞构造-岩浆活动的产物。The Nyainqentanglha granite, a batholith with an area of 1500 km2 in the central Lhasa block, comprises mainly of medium-fine-grained biotite monzonitic granite and medium-coarse-grained biotite monzonitic granite. K-Ar dating, Rb-Sr dating, SHRIMP U-Pb dating of representative samples of the batholith shows that the crystallization age of the medium-fine-grained biotite monzonitic granite is 8.49±0.14 Ma, 8.07±0.35Ma and 8.70±1.40 Ma, 18.3±0.4 Ma and that of the medium-coarse-grained monzonitic granite is 9.80±0.35 Ma, 9.33±0.41 Ma, 11.01±0.24 Ma. The emplacement and crystallization of the Nyainqentanglha granite, the youngest granite batholith ever known inside the Lhasa block, have a close relationship with the collisional orogeny, crustal thickening, plateau uplifting, E-W crustal extension and have a dynamic genetic relationship with the crustal partial melting.

关 键 词：同位素年龄测定 唐古拉 地质意义 SHRIMP 二长花岗岩 等时线年龄 拉萨地块 同位素测年 黑云母 花岗岩体 岩石样品 高分辨率 高灵敏度 青藏高原 局部熔融 岩浆来源 岩浆活动 碰撞构造 单矿物 当雄县 侵入岩 代表性 探针法 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]