阿扎德克什米尔蓝宝石的包裹体拉曼光谱研究

Raman Spectroscopic Study on Inclusion in Sapphire from Azad-Kashmir

  • 摘要: 最初,传统意义的克什米尔蓝宝石仅指产于“Jammu and Kashmir”的蓝宝石,但近期越来越多相邻的地区会被叫做“克什米尔”,特别是产自巴基斯坦控制的阿扎德克什米尔(Azad-Kashmir)地区的蓝宝石。但两个产地蓝宝石的价格有着较大的差异,故准确的鉴定两者产地有着非常重要的意义。采用激光拉曼光谱仪测试技术对阿扎德克什米尔蓝色和紫色蓝宝石样品的包裹体及相关谱学特征进行研究。结果表明,阿扎德克什米尔蓝色蓝宝石和紫色蓝宝石样品的包裹体相似,均含有石墨-气液包裹体组合,锆石与石墨组合,蓝色-紫色平行角状条带与生长纹。此外,蓝色蓝宝石样品中还发现管状包裹体等典型特征,紫色蓝宝石样品还出现了赤铁矿,水铝矿固体包裹体。阿扎德克什米尔蓝宝石的包裹体特征为其提供了产地鉴别的可能。阿扎德克什米尔蓝宝石样品中石墨包裹体拉曼光谱的分析表明,其石墨包裹体结晶程度高,结晶度等级多为三,少数为二级,未出现结晶程度一级。根据石墨拉曼光谱的G(1 580 cm-1)、D1(1 350 cm-1)、D2(1 620 cm-1)因子,应用碳物质拉曼光谱温度计计算石墨的形成温度表明,阿扎德克什米尔蓝宝石母岩的变质峰期温度在600 ℃以上。

     

    Abstract: Initially, sapphire from Kashmir only refers to the sapphire from Kashmir valley located in "Jammu and Kashmir". But recently, the locality has been expanded to encompass some neighboring areas, such as Azad-Kashmir controlled by Pakistan. However, there is a significant price difference between the classical Kashmir sapphire and other Kashmir sapphires. Therefore, it became essential to identify the specific origin of Kashmir sapphire.The inclusions and spectral characteristics of blue and purple sapphires from Azad-Kashmir were studied by micro-Raman spectrometer in this study. The test results show that the blue and purple sapphires bear similar inclusions, and they both contain zircon and graphite mineral inclusions. The typical inclusions are gas-liquids associated with graphite inclusion, as well as zircon, and graphite composite inclusion. Distinct blue-purple parallel angular bands and growth striations are observed. In addition, tube-like inclusions are found in blue sapphires. Hematite and diaspore crystal inclusions are found in purple samples. All the mineral inclusions mentioned above are identified by the micro-Raman spectrum. Further analysis of the graphite Raman spectrum was conducted in terms of the crystallization of the graphite. The results show that most graphite can be classified into medium to high crystallization grade, with no graphite showing a low crystallization level. Based on the G (1 580 cm-1), D1(1 350 cm-1), and D2 (1 620 cm-1) factors derived from the Raman spectrum of graphite, we apply the carbon material Raman spectroscopy thermometer to calculate the formation temperature of graphite. The results show that the peak metamorphic temperature of Azad-Kashmir sapphire parent rock is over 600 ℃.

     

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