Application Of Hydrothermal Diamond-anvil Cell On Beryllium Mineral Crystallization Experiment Study

Beryl and phenakite are the crucial industrial minerals and also the precious gemstones in the beryllium deposit.Their crystallization conditions have critical indicative significance in the study of ore-forming environment,mechanism of beryllium deposits and artificial synthesis.This dissertation make use of the latest hydrothermal diamond-anvil cell(HDAC,type VT)to carry out the crystallization experiment of typical beryllium minerals-beryl and phenakite.In comparison of the traditional high temperature and high pressure experimental apparatus which need their loaded sample quench under the high temperature,hydrothermal diamond-anvil cell can make the in-situ observation on crystallization of the mineral samples and effectively reduce the error.The experiments record the the crystallization conditions of beryllium minerals,including temperature,pressure and some kinetics parameters.We also discussed the migration and precipitation mechanism of Be element in aqueous solution and the correspondent geological significance.The paper has achieved the following main achievements and understandings:(1)The results showed that beryl crystallized at range of 495~869??2.2~10kbar and phenakite crystallized at the lower limit of 467??2.8~6.4kbar,while it can continuously grow under condition of 870??13 kbar which was the upper limit of the experimental equipment.Compared to beryl,phenakite tend to crystallize at a higher temperature range.The diffusion and content of Be,Si and Al in the aqueous system were likely the main factors that enfluence the crystallization habit and crystallization condition of the beryllium minerals.The presence of Al component inhibited the formation of phenakite to a certain extent.(2)In the aspect of crystallization kinetics,crystal nucleated in two types of environment which were flux-rich and silicate-dissoling aqueous fluid and silicate melt.Crystals in the former environment was easy to form a large euhedral crystal,while in the later environment crystals grew into tiny xenomorphic crystals in a large amount.The highest growth rate of phenakite in aqueous solution was 8.02×10-6 cm/s which was equivalent to previous study on the rate in pegmatite.This proved that the silicate aqueous solution was the ideal medium for mineral crystallization.The nucleation and growth of the crystals in aqueous solution are affected to a certain extent by the cooling rate and the saturation of the silicate melt of the system.The lower cooling rate and the lower silicate melt saturation may contribute to forming into euhedral crastals in a higher crystal growth rate and may have less nucleation number in the system(3)Be is sufficiently soluble and gave a obvious migration and precipitation in the OH--contained?CO32--contained aqueous solution system.In the CO32-system,the solubility of Be is higher and easy to precipitate into Be-minerals.