PHASE TRANSITIONS IN ZIRCON IN 2M Na_2 CO_3 SOLUTIONS AT ELEVATED

摘要

Experimental investigation of the stability of metamict and crystalline zircons during the hydrothermal treatment in 2M Na_2 CO_3 solution at T=400-800 deg C, P=1 and 5 kbar were performed. The zircon matrix recrystallization is accompanied by reducing number of imperfections homogenization of main elements and impurity contens and by loss of impurities wich become slightly soluble. Initially Na saturation of zircon matrix causes crystallographic variations and then formation and growth Zr-Na-Si-phase crystals (above 12 wt. Percent of Na). The phase transformations of zircon into baddeleyite begins in metamict zircon at 400 deg C, 1 kbar and in crystalline zircon at 600 deg C, 1 kbar.