新疆达布达祖母绿环带特征与生长不均一性分析  

Growth heterogeneity and zonation characteristics of emeralds from Davdar,Xinjiang

作　　者：崔笛 吴穹 廖宗廷[1,2,3] 亓利剑 周征宇[1,2,3] 张灵敏 钟倩[5] 刘奕岑 李凌 CUI Di;WU Qiong;LIAO Zongting;QI Lijian;ZHOU Zhengyu;ZHANG Lingmin;ZHONG Qian;LIU Yiceng;LI Ling(School of Ocean and Earth Sciences,Tongji University,Shanghai 200092,China;Laboratory of Gem and Technological Materials,Tongji University,Shanghai 200092,China;Shanghai Engineering and Technology Research Center of Gem and Material Technology,Shanghai 200092,China;Guizhou Education University,Guiyang 550018,China;Hubei Relics Archaeology Institute,Wuhan 430077,China)

机构地区：[1]同济大学海洋与地球科学学院,上海200092 [2]同济大学宝石及工艺材料实验室,上海200092 [3]上海宝石及材料工艺工程技术研究中心,上海200092 [4]贵州师范学院,贵州贵阳550018 [5]湖北省文物考古研究所,湖北武汉430077

出　　处：《地学前缘》2023年第2期401-414,共14页Earth Science Frontiers

基　　金：上海市科委科研计划项目(18DZ2281300)。

摘　　要：本文以新疆达布达有生长环带的祖母绿为研究对象,采用宝石显微镜、偏光显微镜、电子探针和X射线衍射等研究方法对其化学成分、环带显微结构及化学微区进行测试。显微结构揭示了环带核部碎裂溶蚀而边部相对完整的阶段性生长证据。X射线衍射数据表明:新疆祖母绿为“八面体”绿柱石,以镁铁质离子对Al的类质同象替换为主,以钠离子为主的碱金属离子作为电荷补偿存在绿柱石通道中;新矿和老矿核部→边部呈碱金属递减趋势,新矿祖母绿样品(N=1)碱性程度偏低(碱金属含量<1%),老矿(N=3)碱性程度中等或较高(1%<碱金属含量<2%或>2%);生长环带包括多重交替色带和核浅边深类型,化学成分研究表明以Cr或V为主要致色元素;生长微区化学层面的不均一性总体反映致色离子、碱金属离子和镁铁质离子物质贡献的差异。The chemical composition, microstructure and element-mapping characteristics of the color-zoned emeralds from Davdar, Xinjiang are investigated using gem microscope, polarized microscope, electron microprobe(EPMA) and X-ray diffraction techniques. The microstructure reveals reliable evidence of periodic growth, which shows the emerald core is fragmented and corroded and the rim is relatively complete. X-ray diffraction data indicate that the Davdar emeralds can be assigned to “octahedral” beryl, with Al substitutions mainly by mafic ions, and alkali ions, mainly Na, occupying the beryl channels for charge compensation. Chemical composition analysis shows the alkali metal contents decrease from the core to the rim in both new and old mine samples. The alkalinity of new mine samples is low(alkali metal <1%), while old mine samples have medium or high alkalinities(alkali metal between 1%-2% or > 2%). The growth zoning types include multiple-color or colorless core-green rim types, and Cr and V are the dominant coloring elements;and chemical heterogeneity of the growth microzones reflects the variable contributions from coloring ions and alkali and mafic ions.

关 键 词：达布达祖母绿 X射线衍射 EPMA 环带特征 不均一性 

分 类 号：P575.1[天文地球—矿物学] P575.3[天文地球—地质学] P578.969