钻石产地特征研究在了解地幔演化及遏制国际冲突钻石非法交易等方面具有重要意义, 采用傅里叶变换显微红外光谱技术对采自中国三个商业性产地的14片天然IaAB型钻石进行了系统的面扫描分析, 根据显微红外光谱谱图定量计算出钻石中的氮含量(1 616个红外测试数据)并进行填图示踪。 结果表明, 钻石生长过程中氮的含量和聚集度不断变化, 且成核阶段氮含量可高于或低于其他生长阶段, 不同生长阶段氮杂质含量不具有单向变化规律, 显示钻石生长过程中地幔流体碳和氮存在复杂的交换, 不同产地钻石中氮含量频率分布及NB%/N(T)特征存在一定的区域性差异, 与跳点法红外光谱测试相比, 面扫描法填图能更直观和连续的示踪钻石生长过程中氮杂质的不均匀生长。

The geographic locality determination of diamonds is of great significance in understanding the mantle evolution, restricting the illegal trade of conflict diamonds, etc. In the present article, the in-situ analysis of micro-FTIR surface scan technique was first applied to analyze 14 IaAB natural diamond specimens from China’s three commercial localities. According to the FTIR spectra of diamonds, the nitrogen contents were calculated (1 616 data points of FTIR) and used for mapping tracer. The results showed that the nitrogen contents and its aggregation often varied in the process of diamond growth, and the nitrogen contents in initial nucleation stage could be higher or lower than in other stages. It is not an unidirectional variation for nitrogen contents in different growth stages, indicating that the carbon and nitrogen had a complex exchange with mantle fluid during the diamond’s crystallization course. It was regionally different between the diamonds from the three localities in the frequency distribution of nitrogen contents and NB%/N(T). Micro-FTIR mapping is more intuitive than the method of selecting discontinuous points, and it can trace the heterogeneous growth of nitrogen impurities in natural diamonds consecutively.