河北唐河透闪石玉的宝石学特征及矿床成因

通过电子探针、X射线粉末衍射、拉曼光谱、化学全岩分析以及显微镜镜下观察,确定了唐河透闪石玉的主要矿物组成为透闪石,透闪石的质量分数一般在80%以上,部分在95%以上,以纤维交织结构为主;杂质矿物有碳酸盐、石英、透辉石、滑石、褐铁矿等,质量分数少于20%。唐河透闪石玉相对和田玉,颗粒较粗,密度和硬度稍低,光泽稍差。通过氢、氧、硅同位素分析以及岩浆岩、围岩和矿石的稀土元素配分模式表明,其岩浆岩(花岗岩)只提供了成矿热液(H2O),Mg、Ca、Si主要来源于白云石和硅质条带或结核;通过包裹体测温推测其为中温成矿。经过分析研究,认为唐河透闪石玉为中酸性岩体与白云质大理岩的接触交代产物。

Study on Gemmological Characteristics and Ore Genesis of Nephrite from Tanghe,Hebei Province

In recent years, a kind of nephrite from Tanghe has been discovered by some won- derful stone amateurs in Tanghe basins of Baoding, Hebei Province, which was called ＂Tangheyu＂ by the locals. However, it has not been studied whether the structure and qual- ity of nephrite from Tanghe are corresponding with nephrite. In a field trip of local regional geology of the mine from Tanghe, the samples were collected. In this paper, the gemmologi- cal, mineralogical and petrology characteristics of the samples from Tanghe are systematical- ly studied. It is roughly confirmed that the origins of nephrite from Tanghe are the contact zones between intermediate-acid granodiorite or granite and dolomitic marble, which locate in the stratum of Miwushan Group Jixian Period and Gaoyuzhuang Group Changcheng Period. With the help of electron microprobe, X-ray powder diffraction spectrometer, Raman microspectrometer, whole rock chemical test and gem microscope, the results show the main mineral component of samples from Tanghe is tremolite,and its content is over 80%, even 95 %. The main structure is fiber-like cryptocrystalline ballistic texture. The contents of impure minerals are less than 20%, including carbonate, quartz, diopside talc limonite, et al.Compared with Hetian Yu from Xinjiang, the nephrite from Tanghe is coarser in structure, with lower value in density and hardness, and shows poorer in surface gloss. The ore-forming solution in nephrite from Tanghe was studied by means of hydrogen i- sotope, oxygen isotope, silicon isotope analyses and the rare earth distribution of pattern of magmatic rock, surrounding rock. The results show that the ore-forming hydrothermal is mainly origined from magmaticrock, mainly granite, and the Si element is mainly origined from dolomitic siliceous hands or tuberculosis. In conclusion, the nephrite from Tanghe is the granite and dolomitic marble of the contract metasomatic deposit, which is similar to de posit of Helian Yu from Xinjiang.