YAN Ruo-gu1，4, QIU Zhi-li1，3*, FENG Ming2, JIN Chun-mei1，3, LI Liu-fen1，3, SHI Gui-yong4, WANG Ping1
1. Department of Earth Science, Sun Yat-sen University, Guangzhou 510275, China 2. Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China 3. Guangdong Provincial Key Lab of Geological Processes and Mineral Resource Survey, Guangzhou 510275, China 4. Enterprise Management Institute of Social Science Academy of Guangdong Province, Guangzhou 510610, China
Abstract：Weathering & transporting and depositing processes may improve the quality of some natural low-quality jadeite through reaction with surrounding water fluids. But the mechanism of such water-rock reaction has not been known clearly to date. Applying microscopic Fourier transform infrared spectroscopy (Micro-FTIR), this paper carried out comparatively in-situ research of jadeites’ mineral composition before and after water-rock reaction. The results show that water-rock reaction cannot impact jadeites in their major and minor element composition, but greatly change their water content. Jadeites became richer, with even several times increase, in water content, after experiencing water-rock reaction, and hence show a shift of absorption peak at 3 550 cm-1 to higher frequency. The mineral crystals of these jadeites showed reglar variation in water content from core to edge, and these jadeites have more water in marginal area than in center area, being opposite to the change in water content in jadeite during high temperature and pressure metamorphic process, hence implying that there are different mechanism and shift direction for H+/OH- of jadeite between high pressure metamorphic process and low temperature water-rock reaction. We think that this finding may contribute to understanding the behavior of water in jadeite during metamorphic process and the mechanism of jadeite quality improvement.
Key words：Water-rock reaction;Jadeite(Feicui);Microscopic Fourier transform infrared spectrum;Structural water
