湖南砂矿金刚石包裹体原位测试:对金刚石成因来源的启示  

In-situ Analysis of Mineral Inclusions in Alluvial Diamonds from Hunan: Insights into the Provenance and Origin of the Diamonds

作　　者：丘志力[1,2] 王琦[1,2] 秦社彩[1] 袁姝[1,2] 孙媛[1,2] 陆太进[3] 李榴芬[1,2] 张健[3] 

机构地区：[1]中山大学地球科学与地质工程学院,广东广州510275 [2]广东省地质过程与矿产资源探查重点实验室,广东广州510275 [3]国土资源部珠宝玉石首饰管理中心,北京100013

出　　处：《大地构造与成矿学》2014年第3期590-597,共8页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(批准号:41272086;40073021);国土资源部公益性行业科研项目(编号:200811012)联合资助

摘　　要：包裹体是探究矿物结晶生长过程及其地球化学环境的重要探针,是反演寄主矿物形成机制及形成环境的有效工具。本文采用显微激光拉曼光谱、电子探针和LA-ICP-MS技术对来自湖南沅水流域的24颗宝石级金刚石的包裹体进行了原位分析。结果显示,湖南砂矿金刚石中橄榄岩型和榴辉岩型包裹体比例接近,橄榄岩型和榴辉岩型包裹体可在同一颗金刚石中＂共存＂;湖南金刚石形成时地幔的温度和压力分别为1109-1237℃和4.05-5.83 GPa,相应的形成深度大致为133-192 km;包裹体成分及组合特征显示,扬子克拉通金刚石的形成环境与华北克拉通金刚石有显著差异,前者的形成与榴辉岩的关系更为密切,暗示有古老的地壳物质参与了金刚石的形成过程。Mineral inclusions are important probes to explore the crystallizing process, geochemical environment, and forming mechanism for their host minerals. In-situ microscopic laser Raman spectroscopy, electron microprobe and LA-ICP-MS analysis were carried out on mineral inclusions in 24 gem-grade alluvial diamonds from the Yuanjiang Basin in Hunan province. The results showed that the portions of eclogite- and peridotite-type mineral inclusion assemblages are similar and can be coexist in diamond grains. The calculated temperatures, based on nitrogen aggregation states and their portions, range from 1109 to 1237 ℃, and the forming pressures calculated using Raman barometry range from 4.05 to 5.83 GPa for olivine inclusions in the Hunan diamonds, corresponding to a depth of 133-192 km. Furthermore, the mineral inclusions and assemblages reveal that the Hunan diamonds were formed in a lithospheric mantle environment in the Yangtze Craton, which is distinct from the diamonds from the North China Craton. The Hunan diamonds may be formed in a lithospheric mantle containing abundant eclogite, showing the participation of ancient crustal material in the formation of the diamonds.

关 键 词：湖南砂矿金刚石 包裹体 原位测试 来源 扬子克拉通 

分 类 号：P619.24[天文地球—矿床学] P59[天文地球—地质学]