西藏班戈县江错铁矿正长斑岩锆石LA-MC-ICP-MS U-Pb定年及意义  

LA-MC-ICP-MS U-Pb Dating of Orthophyre from the Jiangcuo Iron Deposit in Baingoin County,Tibet and Its Geological Significance

作　　者：易明筱 赵元艺[2] 汪傲[3] 许虹[1] 李小赛[2] 卢伟 王贤伟[1] 

机构地区：[1]中国地质大学(北京),北京100083 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国恩菲工程技术有限公司,北京100038 [4]中信矿业科技发展有限公司,北京100008

出　　处：《地质学报》2017年第5期1039-1051,共13页Acta Geologica Sinica

基　　金：中国地质调查局地质调查项目"西藏多龙矿床技术经济与环境综合评价"(编号DD20160330);国家重点基础研究发展计划"973"项目(编号2011CB403103)联合资助成果

摘　　要：在班戈县东偏北约100km的江错铁矿采集正长斑岩样品,进行系统的岩相学、地球化学及锆石LAMC-ICP-MS U-Pb定年。结果显示正长斑岩的SiO_2含量变化为59.55%～62.61%,平均值61.52%,Na_2O含量变化为9.31%～10.01%,平均值9.74%;K_2O含量变化为0.107%～0.12%,平均值0.113%,里特曼指数变化范围为5.16～5.36,属于钠质碱性岩系列,是班公湖-怒江缝合带中段班戈地区首次发现的碱性岩。锆石U-Pb年龄为170±2.4Ma,表明其为中侏罗世的产物。综合对比区域地质资料,认为这套正长斑岩应该是班公湖-怒江洋盆开始俯冲早期的不成熟岛弧阶段的产物。Three orthophyre samples were collected from the Jiangcuo iron deposit, which is located 100km northeast of Baingoin County. Petrographic and geochemistry study shows that the orthophyre has a SiO2 content of 59.55%-62.61% （ave. 61.52%） Na2O content of 9.31%-10.01% （ave. 9.74%）, K2O content of 0. 107% -0.12% （ave. 0. 113%）, with the Rittman index ranging from 5.16 to 5.36. This indicates that the rocks belong to sodic alkaline rock series. Alkaline rock of this kind was discovered for the first time in the Ban＇ge area in the middle part of the Bagong-Nujiang suture belt. Zircon LA-MC-ICP- MS U-Pb dating yields an age of 170±2.4Ma at Yanshannian Mid-Jurassic period. Comprehensive study of regional geological comparison shows that the set of orthophyre should be the product of immature island arc of of the Bangong-Nujiang basin at early stage of subduction.

关 键 词：正长斑岩 锆石U-PB年龄 江错铁矿 班戈 

分 类 号：P597.3[天文地球—地球化学] P618.31[天文地球—地质学]