应用扫描电镜-X射线衍射-电子探针技术研究河南淅川绿松石矿物学特征

Application of EMPA-XRD-SEM to Study the Mineralogical Characteristics of Turquoise from Xichuan,Henan Province

河南省淅川县位于我国重要绿松石产区——秦岭东部绿松石矿区东延部分,与淅川毗邻的许多早期考古遗址中出土了大量的绿松石制品,因此淅川绿松石的矿料流布受到许多考古学者的关注。研究淅川绿松石的矿物学特征有助于完善我国不同矿区绿松石矿物学研究,为追溯我国早期绿松石文物的矿料来源提供重要的数据支撑。本文利用偏光显微镜观察、扫描电镜、粉晶X射线衍射等技术对淅川绿松石进行结构研究,辅以电子探针、背散射电子图像观察等方法研究了淅川绿松石的矿物组合。结果表明:淅川绿松石主要由细小的鳞片状、短柱状、板片状微晶集合体组成,可见环带状、结核状、碎斑碎粒状结构;通过对比不同样品的微晶结构,可知其微晶的大小、晶型和分布状态会影响淅川绿松石集合体的致密程度和颜色;淅川绿松石集合体中常见石英、玉髓和铁氧化物,部分样品含有硫磷铝锶矿。通过对比其他矿区绿松石矿物组合,发现淅川绿松石与湖北地区的绿松石矿物组成相近,主要杂质为石英、褐铁矿,明显区别于安徽地区以高岭石为主要杂质矿物的绿松石。

BACKGROUND: The Xichuan turquoise mining area in Henan Province belongs to the east extension of the turquoise metallogenic belt in the junction of Hubei and Shaanxi Provinces. A lot of turquoise artifacts have been excavated in many early archaeological sites near Xichuan.Therefore,the distribution of the Xichuan turquoises has attracted wide attention of many archaeologists.OBJECTIVES: To study mineralogical characteristics of Xichuan turquoise in order to improve the mineralogical study of turquoise in different mining areas in China and provide important data support for tracing the mineral resources of early turquoise artifacts in China.METHODS: Technologies including polarizing micro-scope,scanning electron microscope,X-ray diffraction were applied to study the texture and structure of turquoise. Electron probe microanalysis and backscattered electron imaging were applied to study the mineral assemblage of Xichuan turquoise.RESULTS: Xichuan turquoise,ring-like,nodular and patchy granular was primarily composed of fine scaly,short columnar and lamellar microcrystalline aggregates. By comparing the microcrystalline structures of different samples,it was noted that the sizes,shapes and distributions could affect the densification and color of Xichuan turquoise. Quartz,chalcedony and iron oxide were common in the Xichuan turquoise aggregate. Svanbergite could also be observed in some samples.CONCLUSIONS: By comparing the mineral assemblages of turquoise in other mining areas,it was found that Xichuan turquoise was similar to the turquoise in Hubei Province with quartz and limonite as main mineral impurities,different from the turquoise in Anhui Province with kaolinite as main mineral impurities.