INTERACTION OF METAMICT ZIRCON WITH FLUIDS OF VARIOUS COMPOSITION

Abstract

Interaction of metamict zircon with solutions of various composition (H2O, 1 m NaCl + 0.5 m HCl, 1 m NaCl, 1 m NaHCO3, 0.1 m Na2CO3, 1 m Na2CO3, 2 m Na2CO3, and 1 m NaOH) was examined at temperatures of 25-800°C, pressures of 1 and 5 kbar, and exposure times of 3, 7, and 14 days. The choice of fluid compositions was determined by the fact that aqueous, chloride, and carbonate solutions are the principal components of postmagmatic, metamorphic, and metasomatic fluids that can affect zircon in nature. Occurring in contact with these solutions, metamict zircon congruently and incongruently dissolves competing with the sorption of elements, crystallization of newly formed phases, and the restoration of the crystal structure. The intensities of these processes are controlled by the temperature, pressure, exposure time, and the pH and composition of the solution. © Pleiades Publishing, Ltd. 2007.