新疆天湖东遗址出产绿松石的矿物学特征及原产地溯源研究

Mineralogical Characteristic and Geographic Origin Tracing of Turquoise from Tianhudong Site,Xinjiang

新疆天湖东遗址是目前西北地区发现的年代最早的绿松石采矿遗址,它的发现为研究我国西北地区古代绿松石来源提供了直接的考古学证据。开展天湖东绿松石矿物学特征研究,可为判断该遗址出产绿松石的产源特点和流布提供基础科学数据。鉴于此,采用偏光显微镜、扫描电子显微镜、X射线粉末衍射、电子探针、拉曼光谱等测试方法开展绿松石样品的表面微形貌、矿物组成、化学成分、拉曼光谱等矿物学和谱学特征的研究。结果表明,新疆天湖东绿松石样品多呈微晶鳞片状及微晶纤维状结构,主要以长柱状、针状、板状相互交织结晶生长,杂质可见石英与黑云母,且出产少见的磷灰石。天湖东绿松石与黑山岭绿松石的拉曼光谱测试结果无明显区别,但电子探针检测的主量化学成分结果显示,天湖东绿松石的Al 2 O 3、P 2 O 5的含量均低于标准值,而黑山岭绿松石却均高于标准值,二者在此存在明显差异。

Tianhudong site is the earliest turquoise mining site found in northwest China,which provides direct archaeological evidence for the study of the source of ancient turquoise in northwest China.Studying the mineralogical characteristics of turquoise in Tianhudong can provide basic scientific data for judging the origin characteristics and distribution of turquise produced at this site.In this paper,turquoises samples from mining site were tested by polarizing microscope,scanning electron microscope(SEM),X-ray diffractometer(XRD),electron microprob(EMPA)and Raman sepctroscopy to obtain their mineralogical and spectral characteristics.The chemical compositions of turquoise from Tianhudong are characterized by rich Fe.The SEM results show that the turquoise crystals are mainly in columnar,needle and plate shape.And none of which are very different from turquoise from Heishanling,Xinjiang.The polarizing microscope observation shows that the turquoises from Tianhudong mostly show microcrystalline scale and microcrystal fiber structures.The impurity minerals are characterized by quartz and biotite.Compared with turquoise impurities from different origin and producing area,the turquoise impurities show that the turquoise from Tianhudong are of weathering-leaching characteristics.There is no significant difference between the results of Raman spectra and that of turquoise from Heshanling,The only slight differences may be related to the differences in crystallinity,ion displacement,inclusions,impurity minerals and weathering of the two samples.At the same time through Raman spectra,Tianhudong turquoise is also accompanied with apatite minerals rarely seen in other turquoise mines.This characteristic is unique to turquoise from Tianhudong,and is one of the evidences for distinguishing the origin of turquoise in the future.The electron microprobe analysis indicates that the chemical compositions of turquoise from Tianhudong deviate from theoretical value.The contents of Al 2 O 3 and P 2 O 5 in turquoise from Tianhudong are lower than the standard value,while the turquoise from Heishanling is higher,and there are obvious differences between them.