黑青和田玉宝石矿物学及地球化学特征研究OA北大核心CSTPCD

In recent years,a kind of black cyan nephrite containing pyrite has appeared in the domestic market.It is mainly produced in Xinjiang and belongs to a relatively rare nephrite variety,which has mining and utilization value.This article systematically analyzed the mineralogical and geochemical characteristics of seven samples using conventional gemological instruments,polarized light microscopy,infrared spectroscopy,Raman spectroscopy,X-ray powder diffraction(XRD),electron probe(EPMA)laser inductively coupled plasma mass spectrometry(LA-ICP-MS),and isotope mass spectrometer(MC-ICP-MS).The results show that the color of black cyan neph-rite is dark green to black,the refractive index is 1.61,the relative density is 3.08～3.17,and the Mohs hardness is 6.0～6.5.The main component mineral is tremolite,the secondary mineral is mainly pyrite,and a small amount of chlorite,epidote,sphene,zircon,and graphite are also contained,with a typical fiber interlaced struc-ture;The characteristic peaks of infrared and Raman spectra are consistent with the standard peaks of nephrite;The main chemical components of the sample are SiO2,MgO,CaO and FeO.The Mg/(Mg+Fe2+)value indicates that some tremolite has transitioned to actinolite.Based on the trace element Cr-Ni mapping,the sample is identified as a dolomite marble type genesis,while the content of rare earth elements is relatively low,in a left leaning mode,The ore-forming hydrothermal fluid is mainly magmatic water,containing a small amount of metamorphic water.The sample contains pyrite with Co/Ni＞1 and small amounts of As,Se,Cu,Zn and Pb,δ34Sranges from 8.87％o to 20.92％o,suggesting that it is of magmatic-hydrothermal origin and the source of sulfur is a mixture of magma and formation sulfur.