Micro-FTIR Mapping Tracer for the Heterogeneity Growth of Nitrogen Impurities in Natural Diamond from Three Localities in China
SUN Yuan1, 3, QIU Zhi-li1, 3*, LU Tai-jin2, CHEN Hua2, CHEN Bing-hui1, 3, PENG Shu-yi1, 3, WEI Ran2, LI Liu-fen1, 3
1. Department of Earth Science, Sun Yat-sen University, Guangzhou 510275, China 2. National Gems & Jewelry Technology Administrative Center, Beijing 100013, China 3. Guangdong Provincial Key Lab of Geological Processes and Mineral Resource Survey, Guangzhou 510275, China
Abstract：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.
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