碧玺的宝石学特征及其内部包裹体研究

发布时间：2018-05-02 16:22

  本文选题：成分特征 + 谱学特征　； 参考：《成都理工大学》2017年硕士论文

【摘要】：碧玺的矿物学名称为电气石,是晶体结构和化学成分十分复杂的含硼硅酸盐,类质同像替代广泛,形成环境的变化以及所含微量元素的不同,使得碧玺颜色十分丰富,几乎所有的颜色以及颜色组合都能看到。电气石并不是只有单一的的种类,而是一个矿物族,电气石的主要矿物种类已确定的有18种,如铁电气石、镁电气石等,大部分宝石级电气石(碧玺)是锂电气石。本论文采用宝石学常规测试、宝石显微镜、偏光显微镜、电子探针、红外光谱仪、激光拉曼光谱仪、冷热台等对不同颜色碧玺的化学成分、谱学特征和包裹体进行研究,并探讨其生长条件和演化过程。通过宝石学常规测试,所选样品与碧玺的光学和力学性质基本符合,黑色碧玺相对密度较其它样品高。部分样品的相对密度偏低,并且在紫外荧光灯下出现了不同强度的蓝白色和白色荧光,与碧玺经过充填处理有关。可以通过宝石显微镜观察样品表面特征和内部特征,鉴别碧玺是否经过充填处理。通过电子探针测试分析,除一块棕色碧玺样品属于镁电气石外,其余均属于锂电气石,棕色—黑色系列碧玺颜色较深,透明度不好,常不用来作为宝石,所以说宝石级电气石—碧玺主要为锂电气石。选取不同颜色的碧玺进行红外光谱测试,测试结果符合锂电气石的红外光谱特征,红外光谱还显示碧玺表面存在着对大气中水蒸气、甲烷和二氧化碳的吸收。对不同碧玺样品的主体矿物、流体包裹体和固体包裹体进行激光拉曼测试,Fe含量的增加,会导致Si-O伸缩振动的拉曼峰和3590cm-1附近[OH]-拉曼峰发生分裂,也会抑制3650cm-1附近的拉曼峰;气液包裹体中特征拉曼峰的存在指示包裹体中存在CO_2、CH_4等气体在偏光显微镜下观察碧玺内部包裹体特征。除针状和管状包裹体外,其他包裹体较小,数量少,形态不规则,随机分布。管状包裹体内常被次生矿物和气液充填。测定流体包裹体的均一温度、冰点及笼合物熔化的温度,通过对测试数据的分析和计算可知成矿流体的物理化学条件:温度范围为198~392℃,盐度范围为2.41~5.41wt%,压力范围为518.6×105Pa~722.4×105Pa,低盐度与碧玺较低的结晶温度相一致。
[Abstract]:The mineralogical name of the tourmaline is tourmaline, which is a boron-bearing silicate with very complex crystal structure and chemical composition. Almost all colors and combinations of colors can be seen. Tourmaline is not a single species, but a mineral family. There are 18 kinds of tourmaline minerals, such as ferrotourmaline, magnesium tourmaline, etc. Most gemstone tourmaline (tourmaline) is lithium tourmaline. In this paper, the chemical composition, spectral characteristics and inclusions of different color tourmalines were studied by conventional gemstone test, gemstone microscope, polarizing microscope, electron probe, infrared spectrometer, laser Raman spectrometer, cold and hot stage, etc. The growth conditions and evolution process were also discussed. The results show that the optical and mechanical properties of the selected samples are in good agreement with those of the other samples, and the relative density of the black tourmaline is higher than that of the other samples. The relative density of some samples was low, and different intensity of blue and white fluorescence appeared in UV fluorescent lamp, which was related to the filling of the tourmaline. The surface and internal characteristics of the sample can be observed by gem microscope to identify whether the tourmaline has been filled. Through the electron probe test analysis, except one brown tourmaline sample belongs to the magnesium tourmaline, the rest belongs to the lithium tourmaline, the brown-black series tourmaline is dark color, the transparency is not good, often does not need to be used as the gem, Therefore, gemstone-tourmaline-tourmaline is mainly lithium tourmaline. The infrared spectra of different colors of tourmaline were tested, and the results were in accordance with the infrared spectra of lithium tourmaline. The infrared spectra also showed the absorption of water vapor, methane and carbon dioxide on the surface of tourmaline. The increase of Fe content in the main minerals, fluid inclusions and solid inclusions of different tourmaline samples will result in splitting of Raman peak of Si-O stretching vibration and [OH] -Raman peak near 3590cm-1, and will inhibit Raman peak near 3650cm-1. The existence of characteristic Raman peaks in gas-liquid inclusions indicates that there are gas inclusions such as COD _ 2 and Ch _ 4 in the inclusions. The characteristics of inclusions inside the tourmaline are observed under a polarizing microscope. Except for needle-shaped and tubular inclusions in vitro, other inclusions are small, small in number, irregular in shape and randomly distributed. Tubular wrapping is often filled with secondary minerals and gas-liquid. The homogenization temperature, freezing point and melting temperature of the fluid inclusions are measured. The physical and chemical conditions of the ore-forming fluid are obtained by analyzing and calculating the test data: the temperature range is 198 ~ 392 鈩，

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