Thermodynamic research of jadeite jade at high temperatures and high pressures based on phase balance intelligent calculation

Abstract

Based on the thermodynamic calculation of chemical composition and the intelligent calculation of phase equilibria, the temperature-pressure of the diagenetic environment of Burma jadeite-jade was studied, and its metamorphism was ver?ified. Firstly, the Wkj value and activity of the four end-member of jadeite (Jd), augite (Acm), diopsite (Di), and hedenbergite (Hed) were calculated. Jadeite rock system was simplified as NCFMASH, and the equilibrium temperature-pressure conditions of both the combination of quartz and jadeite, sodium-feldspar with little kyanite, and the combination of jadeite diopside, hedenbergite, kyanite, sodium-tremolite, tremolite and oblique zoisite were revealed as 751?C with 17.0 kb, and 631?C with 18.8 kb. Based on the two kinds of mineral combination with a small amount of sodium mica [Pa], the balance of the system temperature should be in the range from 700-770?C, and balanced pressure-range should be in the range from 17.34-18.83 kb, which reflects the pure NCFMASH system hard rock type jadeite-jade rock formation of the real balance temperature-pressure range. It is concluded that the metamorphism of jadeite rock has a stable growth equilibrium temperature-pressure range, which is the reaction interval of the closed system NCTNASH. It is explained that the reason that synthetic jadeite-jade reaches the gem level is that it has not been simulated as a mineral assemblage in the later stage and it will be subjected to multi-phase dynamic metamorphism after the rock forms, so it is unreasonable that jadeite synthesize is not just from one mineral crystals.