Studies Of Inclusions And Zonal Characteristics Of Emeralds From Malipo,Yunan Province,China

In this research,based on field work in Malipo in Yunnan province,inclusions and zonal characteristics of emeralds are studied by gemological methods,polarized microscope,electron probe?EPMA?,LA-ICP-MS,cathodoluminescence?CL?,FTIR micro-spectroscopy,laser raman spectroscopy,UV-Vis spectrophometer and microscopic heating/cooling Stage.There are two occurrences in Yunnan emeralds:pegmatite veins and shear zone veins.Chemical composition of emeralds differences in these two occurrences:emeralds in shear zone veins contain more Cr₂O₃,which lead to a greener appearance.Emeralds in pegmatite veins contain more V₂O₃.Emeralds in shear zone veins contain more abundant inclusions.Inclusions which can be considered as origin characteristics:black dravite,vanadium muscovite,zonal feldspar,arsenopyrite,magnesium biotite,scheelite.Additionally,Yunnan emeralds contain a large amount of albite,pyrite,quartz,calcite,sphene,zircon,apatite,fluorite,chlorite,emerald inclusions.Diopside,epidote,sphalerite,galena are discovered occasionnally.Fluid inclusions in mineralization stage of Yunnan emeralds are divided into three types:two-phase inclusions?Type??,three-phase inclusions bearing CO₂?Type??,three-phase inclusions bearing daughter minerals s?Type??.Studies shows that ore-forming fluid characterized with middle-high homogenization temperature and middle-low salinity.Differences appear in two type pegmatite veins,which indicates that there are at least two stage mineralization respectively in quartz vein and feldspar vein.Yunnan emeralds have characteristic concentric hexagon color zone and straight color zone perpendicular to axis c.In this study,major elements,trace elements,and rare earth elements are analyzed and the causes of color zone are discussed.FTIR micro-spectroscopy shows that 3600 cm^-1 symmetric stretching vibration?s of type?H₂O and 1637 cm^-1 bending vibration?of type?H₂O appear stronger in white zones in Yunnan emeralds,which indicates white zones contain more type?H₂O than green zones.Moreover,the result confirms there are more alkali metal in white zones,consistent with EPMA and LA-ICP-MS results.The UV-Vis spectra of 410⁴80nm 590⁶80nm wide and strong absorption bands are caused by V³⁺,and characteristic V³⁺are 610nm and 430nm.Green zones in zonal emerald show characteristic Cr³⁺absorption band.