Study On Fluid Inclusions In Beryl From Pegmatite Of Xinjiang And Inner Mongolia

Beryl is an important gem mineral and main source of beryllium which has significant strategic importance in mineral resources. China is celebrated for beryl, but few beryl deposits can be exploited to become gem resources. Pegmatite-type deposit of beryl in Inner Mongolia which was found in1970s has great potential to be exploited. And the deposit of beryl has similar geological background and occurrence to Xinjiang Altay. However, there's almost no previous information to guide. So the intensive researches on formation causes of beryl from Xinjiang Altay and Inner Mongolia have great significance in seeking beryl gem resources in Inner Mongolia.This article studied on fluid inclusions in beryl and paragenetic apatite from pegmatite of Xinjiang Altay and Inner Mongolia. By comparing and analyzing the similarities and differences of type, characteristic, mineralization temperature, salinity, density, pressure and gas-liquid composition of fluid inclusions from the two places, we can explain beryl's crystallization period, analyze their genetic physics and chemistry conditions, approach to deposit genesis and supplement related information.By means of EPMA, we found that beryls from two places have similar chemical composition and the contents of silicon and aluminum in beryl are a little lower than standard chemical formula. The results of micro-temperature measurement showed that the ore-forming fluids are of the NaCl-H2O and NaCl-CO2-H2O types. Main types of fluid inclusions in the two places include gas-liquid inclusions, carbon dioxide three-phase inclusions and pure-liquid inclusions which point to hydrotherm phase. The homogenization temperatures are concentrated in the range of 150～280℃, the salinities w (NaCleq) are in the range of 5～10%, the pressures are in the range of 20～40×105Pa. So the fluids belong to low-medium temperature and low-medium salinity fluids. And by Laser-Raman Spectrum, we found some organic gas in beryls which proves the liquid immiscibility. In view of above-mentioned results, we suppose that the beryl deposits in two places possess the same genesis and probably went through hydrotherm phase. Researches showed that the fluid inclusions in paragenetic apatite from Inner Mongolia have different features. The homogenization temperatures are concentrated in the range of 270～450℃, the salinities w (NaCleq) are in the range of 9～13%, the pressures are in two separated ranges of 5～18×105Pa and 240～18×105Pa. In view of these, we suppose that paragenetic apatite formed earlier than the beryl in the same deposit, and probably went through second-period or multi-period metallogenesis or hydrotherm phase.