Study On Mineralogical Characteristic And Fluid Inclusions Of Aquamarine From Fugong,Yunnan Province

The mineralogical characteristic and the fluid inclusions of aquamarine from Fugong Yunnan province were studied in this paper,using modern testing technology of Eectron-probe,X-ray powder diffraction,Infrared spectrum,UV-visible absorption spectroscopy,Laser Raman spectroscopy and Microscopic measurement.The electron-probe-derived compositions of the Yunnan Fugong aquamarine suggest that the Al concentration is on the low side whereas the Si concentration is on the high side,the Al concentration decrease when the Fe and Mg concentration increase.There is the replacement of A13+ by Mg2,Fe2,Fe3+ and Mn2+ in the octahedral site,besides there are some microelements such as V3+,Cr3+ and Ti4+substitute the Al3+.In the tetrahedral site there is the isomorphic substitution of Be2+by Li+.The analytic results of the X-ray powder diffraction show that there is a little quartz in the aquamarine except for the palasome.The cell parameters indicate that the aquamarine of Yunnan and Xinjiang province should be assigned to "common"beryl class,the high amount of alkali metal ions locate in the channel architecture or there is structural substitution by minute quantity of alkali metal ions.The infrared reflection spectrum of aquamarine show that the inner structure of aquamarine of different colors don't have evident change,and the structure of Yunnan aquamarine is similar to the structure of Xinjiang aquamarine.The infrared transmitted spectrum of aquamarine show that there are two different types of water molecules(water type ? and water type II)in the channel architecture of Yunnan and Xinjiang aquamarine.In the direction vertical to the C-axis,the vibration of water type ? is very faint.Besides,the multiple polymerization ion[Fe2(OH)4]2+ is characterized by the stretching vibration at 3236cm-1 in the direction parallel to C-axis,and at 2363cm-1 there is the asymmetric stretching vibration of CO2 molecules in the direction of both parallel to C-axis and vertical to C-axis.The UV-visible absorption spectroscopy of Yunnan Fugong aquamarine of different colors in different directions is examined.It's found that there is a strong and broad absorption band near at 815nm,which illustrates that Fe2+ is not only in the octahedral site but also in the channel site.The absorption band at 695nm(?C)is attributed to the Fe2+/Fe3+ interaction.The weak absorption band at 430nm arises from the Fe2+ which substitutes the Al3+ in the octahedral site.The Fe2+ in the octahedral site produces the color of the aquamarine,and the Fe2+/Fre3+ interaction also makes a weak effect,but it doesn't have much relationship with the channel Fe2+.The inclusions of Yunnan Fugong aquamarine are mainly three-phase fluid inclusions of gas-liquid-solid.The size of the fluid inclusions is 26×25?143×85?m,and the gas-liquid ratio is 5%?55%.By the means of Laser Raman spectroscopy test and analysis,it's found that the fluid inclusions' gas components are CO2,H2O and a small amount of CH4,the liquid components are carbonate saline solutions with some liquid CO2,the solid matted crystals are carbonates.The micro-thermal results show the homogenization temperatures of gas-liquid phase are between 290.6? and 362.8?,relatively concentrate on 340?370?,and the freezing temperatures are in the range of-2.7?+-8.8?.The fluid inclusions are inclusions with supersaturated saline solutions,their trapping temperatures are above 450?,which belong to high salinity,moderate and high temperature fluid inclusions.