ANALYSIS OF CONSTITUTION WATER NON-UNIFORMITY AND DIAGENESIS OF THE JADEITE FROM HPAKANT AREA IN MYANMAR

The jadeitite originating from Hpakant region in Myanmar is a crystallized product created in the subduction region with low temperature and high pressure with the involvement of multi-stage fluid. The micro-FTIR and electron microscope have demonstrated that traces of constitution water commonly exist in nominally anhydrous jadeite from Hpakant and TawMaw areas in Myanmar and the water exists in the form of M-OH. The infrared absorption bands caused by M-OH stretching vibration are located within the wave number ranging from 3570 to 3520 cm-1, from 3340 to 3310 cm-1 and from 3230 to 3140 cm-1, respectively. The micro-constitution water in single jadeite grains tends to unite with positive ions of Ca, Fe and Mg elements in the position of MI and MII in the crystalline structure. In addition, the non-uniformity in the constitution water content and the chemical constituents commonly exist, suggesting that the content of constitution water and Ca, Fe and Mg elements increases progressively inside-out whereas the content of Al element decreases progressively inside-out. The maximum constitution water content in jadeite can reach 2707.25×10-6 and the minimum level can achieve 1022.66×10-6. A certain degree of coupling relationship exists between these two concentrations. Consequently, the jadeitite in this area probably has experienced plate subduction and metasomatism of multi-stage fluid during the exhumation process.