尼日利亚锌尖晶石的宝石矿物学及包裹体特征研究  

Gem mineralogy and inclusion characteristics of gahnite from Nigeria

作　　者：陈仪方 金雪萍 刘子琪 周征宇[1,2,4] 郑浚豪 管琪韵 陈琦 CHEN Yifang;JIN Xue-ping;LIU Zi-qi;ZHOU Zheng-yu;ZHENG Jun-hao;GUAN Qi-yun;CHEN Qi(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;College of Ocean and Earth Sciences,Tongji University,Shanghai 200092,China;College of Humanities,Tongji University,Shanghai 200092,China;Laboratory of Gemstone and Process Materials,Tongji University,Shanghai 200092,China)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092 [2]同济大学海洋与地球科学学院,上海200092 [3]同济大学人文学院,上海200092 [4]同济大学宝石及工艺材料实验室,上海200092

出　　处：《岩石矿物学杂志》2024年第3期619-629,共11页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金项目(49772096);上海市科委项目(18DZ2281300)。

摘　　要：采用常规宝石学测试、电子探针、单晶X射线衍射和拉曼光谱等方法,深入分析了尼日利亚锌尖晶石的常规宝石学特征、化学成分、晶体结构以及包裹体特征。尼日利亚锌尖晶石呈完好的八面体晶形,强玻璃光泽、半透明,相对密度为4.48~4.61,折射率为1.792~1.794,紫外荧光灯下呈惰性。通过电子探针测试,计算其化学式为Zn_((0.87~0.92))Fe_((0.06~0.07))Al_((1.98~2.01))O_(4)。单晶X射线衍射揭示其为立方晶系、空间群Fd3m,晶胞参数a=8.089(2)A,四面体键长T—O=1.953(4)A,八面体键长M—O=1.9129(19)A。锌尖晶石的特征拉曼吸收峰位于418 cm^(-1)和659 cm^(-1),分别对应E_g模式、高频T_(2g(3))模式。包裹体研究显示锌尖晶石含有多种矿物包体,包括闪锌矿、钠长石、白云母、石英、绿柱石、锆石和硅铍石,结合前人研究认为尼日利亚锌尖晶石形成于富Li、Cs、Rb、Be和Ta等元素的花岗伟晶岩中。The conventional gemological properties,chemical composition,crystal structure,and inclusions compo-sition and characteristics of the Nigerian gahnite were analyzed in depth by conventional gemological testing,elec-tron probe,single crystal X-ray diffraction,and Raman spectroscopy.The gahnite exhibits well-preserved octahe-dral crystal morphology,strong vitreous luster,and semi-transparency,with a relative density ranging from 4.48 to 4.61 and a refractive index of 1.792 to 1.794,displaying inert fluorescence under ultraviolet light.The electron probe analysis determined its chemical formula as Zn_((0.87-0.92))e(0.060.07)Al_((1.98-2.0))O_(4) Single-crystal X-ray dffrac-tion revealed a cubic crystal system with space group Fd3m,lattice parameter a=8.089(2)A,tetrahedral bond length T-0=1.953(4)A,and octahedral bond length M-0=1.9129(19)A.Characteristic Raman absorption peaksfor gahnite werei denifed a 48cm^(-1) and 659cm^(-1),coreponding he modeand hgh-reueney T_(2g(3)) mode,respectively.Raman spectroscopy of inclusions confirmed the presence of various minerals in gahnite,including sphalerite,albite,muscovite,quartz,beryl,zircon,and phenacite.Combined with previous studies,it is believed that gahnite in Nigeria is formed in granite-pegmatite rich in Li,Cs,Rb,Be and Ta.

关 键 词：锌尖晶石 宝石学 矿物学 包裹体特征 

分 类 号：P578.46[天文地球—矿物学]