广西大化透闪石玉的宝石矿物学特征研究

发布时间：2018-06-08 08:02

本文选题：广西大化 + 透闪石玉　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：本文对广西大化透闪石玉进行宝石学、矿物学特征研究,推测其矿床成因,并从宝石学特征、成分、结构和成因等方面与其它产地软玉对比,分析各产地之间的差异,为玉石鉴定和开发利用提供指导作用。广西大化透闪石玉颜色主要为青白色、灰绿色,表面有风化现象。多数样品呈微透明至不透明,光泽较弱,为蜡状光泽至弱油脂光泽,内部有白色、黑色斑点状或脉状杂质。通过常规宝石学测试,广西大化透闪石玉的密度范围在2.90~2.97 g/cm3,平均为2.94 g/cm3;测试样品的摩氏硬度范围在5.32~6.06,平均为5.70;折射率范围在1.60~1.62,略低于软玉标准。偏光显微镜下薄片观察,广西大化透闪石玉结构主要有:毛毡状纤维变晶结构、显微纤维变晶结构等;围岩样品为具辉绿结构的辉绿岩和粒状结构的透闪石化白云岩。主要矿物为纤维状、束状的透闪石,次要矿物为粒状的透辉石、方解石、绿泥石、石英,纤维状的阳起石等。扫描电镜观察透闪石玉样品表面微形貌特征,可见透闪石玉为显微纤维交织结构、定向显微纤维结构、显微片状结构。通过傅里叶红外光谱仪、X射线粉晶衍射测试,数据分析结果基本与标准透闪石数据接近,可知其主要化学成分为透闪石。通过电子探针对样品的化学组成进行测试,其化学组成主要为Ca O、Mg O、Si O2,还有Fe O、Mn O、K2O、Na2O、Al2O3、Ti O2等,结合背散射图像观察,样品的矿物组成与偏光显微镜观察结果基本一致,主要为透闪石、透辉石和绿泥石,还有磷灰石、榍石和钙铁榴石等。结合实验数据,推测广西大化透闪石玉矿床属于岩浆热液交代型矿床,其矿床成因是辉绿岩等基性侵入岩及岩浆携带的热液,在一定的温压条件下,与白云质灰岩等碳酸盐岩发生接触交代和热液交代作用。将广西大化透闪石玉的宝石矿物学特征与其他产地软玉进行对比,发现其宝石学性质、成分和结构与其它产地软玉基本一致。由于国标修改了和田玉的命名,和田玉不再具有产地意义,广西大化透闪石玉符合现行的和田玉标准。作为新发现的透闪石玉矿床,商业价值潜力巨大,还需要更深入的研究,为合理开发和利用提供理论支持和技术指导。
[Abstract]:This paper studies the characteristics of gemmology and mineralogy of Dahua tremolite jade in Guangxi, infer the origin of the deposit, and compare the characteristics, composition, structure and origin of the deposit with that of other producing areas in order to analyze the differences between the different areas. To provide guidance for the identification, development and utilization of jade. Guangxi Dahua tremolite jade color is mainly green, grey-green, surface weathering phenomenon. Most of the samples were slightly transparent to opaque with weak luster, waxy luster to weak oil luster, white, black spotted or veined impurity inside. The density range of Guangxi Dahua tremolite jade is 2.90 ~ 2.97 g / cm ~ (-3), the average is 2.94 g / cm ~ (3), the Mohlich hardness range is 5.32 ~ 6.06, the average value is 5.70, and the refractive index range is 1.60 ~ 1.62, which is slightly lower than the standard of nephrite. Under polarizing microscope, the structure of Guangxi Dahua tremolite jade is mainly composed of felt-like fiber metamorphic structure, micro-fiber metamorphic structure and so on, and the surrounding rock samples are diabase with pyrophyllite structure and tremolite dolomite with granular structure. The main minerals are fibrous, bunchy tremolites, secondary minerals are granular diopside, calcite, chlorite, quartz, fibrous actinolite, etc. The microstructure of tremolite jade was observed by scanning electron microscope. It can be seen that tremolite jade has interlaced microstructure, directional microfiber structure and microflake structure. By Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction measurements show that the results of data analysis are basically close to those of standard tremolites, and the main chemical composition is tremolite. The chemical composition of the sample was tested by electron probe. The chemical composition of the sample was mainly CaOMg-OOSiO2, and the chemical composition of the sample was mainly FeOOMn-OK2OK2O-Na _ 2O-Al _ 2O _ 3-Ti _ 2O _ 2. The mineral composition of the sample was basically consistent with that observed by polarizing microscope combined with backscatter images. Mainly tremolite, diopside and chlorite, as well as apatite, sphene and calcium iron garnet and so on. Based on the experimental data, it is inferred that the Dahua tremolite deposit in Guangxi belongs to magmatic hydrothermal metasomatic type. The origin of the deposit is diabase and other basic intrusive rocks and hydrothermal fluid carried by magma under certain temperature and pressure conditions. Contact metasomatism and hydrothermal metasomatism occur with carbonate rocks such as dolomitic limestone. The gemstone mineralogical characteristics of Guangxi Dahua tremolite jade are compared with those of other origin nephrite. It is found that the gemstone properties, composition and structure of Guangxi Dahua tremolite jade are basically the same as those of other origin nephrite. Because the national standard has modified the name of Hotan jade, Hetian jade no longer has the significance of producing area, Guangxi Dahua tremolite jade conforms to the current Hotan jade standard. As a newly discovered tremolite deposit, the commercial value of the deposit has great potential and needs more in-depth research to provide theoretical support and technical guidance for rational development and utilization.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.28

【共引文献】