氦氩同位素对蓝宝石成因的指示  

Genesis of Sapphires Indicated by Helium and Argon Isotopes

作　　者：郭伟 赵倩怡 贺怀宇[1] GUO Wei;ZHAO Qianyi;HE Huaiyu(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;School of Earth Sciences,China University of Geosciences,Wuhan 430074)

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国地质大学(武汉)地球科学学院,武汉430074

出　　处：《中国宝玉石》2022年第1期2-7,共6页China Gems & Jades

基　　金：国家自然科学基金青年基金(41903011)资助。

摘　　要：本文报道了斯里兰卡蓝宝石的氦、氩含量及同位素组成。采用真空压碎法获得蓝宝石流体包裹体中的氦、氩含量分别为3.7~4.9×10^(-6)cm^(3)STP/g和1.6~1.9×10^(-6)cm^(3)STP/g,同位素组成分别为3He/4He=0.17~0.21 Ra和40Ar/36Ar=4348.7~4457.3。该特征与含刚玉的古老变质岩类似,接近纯地壳组分端元,指示其形成于壳内的变质作用过程。与山东省昌乐碱性玄武岩内岩浆成因的蓝宝石对比,发现二者具有显著不同的稀有气体同位素特征,其中昌乐蓝宝石含有强烈的幔源流体特征。提出稀有气体同位素及元素比值可有效判别蓝宝石的成因类型及形成过程。Helium and argon concentrations and isotope compositions of sapphires from Sri Lanka is reported here.The gases released mainly from fluid inclusions by in vacuum crushing consist of 3.7~4.9×10^(-6)cm^(3)STP/g helium and 1.6~1.9×10^(-6)cm^(3)STP/g argon,with3He/4He=0.17~0.21 Ra and 40 Ar/36 Ar=4348.7~4457.3.These signatures are similar to those of the old corundum-bearing metamorphic rocks,and are close to the pure crustal endmembers,indicating that they were formed in metamorphic processes within crust.Compared to Changle(Shandong Province,China) sapphires,which are hosted by Cenozoic alkali basalts and have significant mantle-derived noble gas components,the Sri Lanka sapphires show mainly crustal noble gas compositions.It is proposed that noble gas isotope and elemental ratios can effectively distinguish the genesis and forming processes of sapphires.

关 键 词：蓝宝石 斯里兰卡 稀有气体 氦―氩同位素 

分 类 号：P597[天文地球—地球化学]