H_2O in channel of pegmatitic beryl and its hydrogen isotopic composition

摘要

At present; it is universally accepted that pegmatite can be crystallized from volatile-rich peraluminous residual granitic melt in a relatively elosed environment from liquidus to solidus. However, there still exist controversies on the properties of magmatic/hydrothermal transition, the presence of an independent fluid-phase and internal evolution in the system of equilibrium, the crystallization temperature of mineral structural zones, the time and seale of the occurrence of metasomatosis and the process of rock/fluid interaction. The method of crush-leach analysis of fluid inclusions is still widely used in the study of the properties of magmatic/hydrothermal transition because analysis of single inclusion is limited by the techniques. Thus the results of crush-leach analysis unavoidably encounters the contamination from inclusions of multi-generations. Recently, Taylor and Giuliani et al, successively provided some important information about the volatile evolution (mainly H_2O) of pegmatite and genesis of emerald ore deposits by use of hydrogen isotopic composition of original fluids trapped in channels of beryl and emerald.