岩矿测试2025，Vol.44Issue(6)：1113-1130,18.DOI:10.15898/j.ykcs.202503100040
金膏玉的岩石矿物学特征及颜色成因
Petrological and Mineralogical Characteristics of Jingao Jade and Its Color Genesis
摘要
Abstract
The Jingao jade produced in Luonan County,Shaanxi Province,is named for its distinctive golden color.Currently,the research on the color and genesis of the Jingao jade deposit is still in its infancy and has not yet reached a consensus.The lack of completeness in the research on the origin of color restricts the non-destructive detection of Jingao jade as a gemstone.In order to further clarify the color origin and genesis of Jingao jade,different colored samples were selected and studied by polarized light microscopy,X-ray diffraction(XRD),inductively coupled plasma-optical emission spectrometry/mass spectrometry(ICP-OES/ICP-MS),electron probe microanalysis(EPMA),scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS),laser Raman spectroscopy(LRS),diffuse reflectance spectroscopy(DRS),and stable isotope mass spectrometry.Data demonstrate that Jingao jade mainly consists of dolomite.The unit cell parameters and chemical composition of the dolomite are very close to those of the ideal dolomite.Whole-rock geochemistry and EPMA spot analyses of dolomite both reveal that the Fe content in the yellow jade is significantly higher than that in the white one.First-derivative diffuse reflectance spectra of Jingao jade exhibit characteristic goethite absorptions at 526-538nm and 435-437nm,and the intensity of the yellow hue increases linearly with goethite content.The regular shift of the main peak of dolomite in Raman spectroscopy also indicates that the Fe in dolomite might also contribute to the yellow color.Whole-rock chemical analysis indicates that Jingao jade has not been significantly influenced by terrestrial components and can reflect the environment during the formation period.The average values of δEu and δCe of Jingao jade are 0.956 and 0.818,respectively,indicating a weakly oxidized sedimentary environment.Based on the results of the isotopic analysis of carbon and oxygen(with the average δ13C value of Jingao jade being-0.1896‰ and the average δ18O value being-4.2107‰),the formation model analysis indicates that Jingao jade may belong to burial-origin dolomite.Based on the carbon and oxygen isotope values,the Z value is calculated using empirical formulas to determine the source of the limestone.The average Z value of Jingao jade is 142.746,which is far beyond the discrimination threshold for marine limestone(Z>120 indicates marine limestone,while Z<120 indicates freshwater limestone).This supports the conclusion that Jingao jade was formed by the transformation of limestone with distinct marine origin characteristics,and did not undergo any geological events that might have significantly reduced the carbon and oxygen isotopes(such as sea level drop or freshwater environment)after diagenesis,reflecting a stable marine sedimentary environment.The BRIEF REPORT is available for this paper athttp://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202503100040.关键词
金膏玉/白云石/针铁矿/碳氧同位素/全岩化学分析/海相成因Key words
Jingao jade/dolomite/goethite/carbon and oxygen isotopes/full rock chemical analysis/marine origin分类
天文与地球科学引用本文复制引用
陈倩,张随安,康琴琴,成星,艾昊,贺凯凯..金膏玉的岩石矿物学特征及颜色成因[J].岩矿测试,2025,44(6):1113-1130,18.基金项目
陕西省自然科学基础研究计划项目(2022JQ-258) （2022JQ-258）
陕西省公益性地质调查项目(202507) （202507）
陕西省重点研发计划社会发展领域一般项目(2024SF-YBXM-561) （2024SF-YBXM-561）
