Oxygen and hydrogen isotopic compositions of coexistent minerals of the Tasigake alkali granite pluton, northern Xinjiang: constraints upon the causeof O-18-D depletion and the O-18/O-16 exchange kinetics

Oxygen and hydrogen isotopic compositions have been determined of three coe xistent mineral triplets of alkali Feldspar, quartz, arfvedsorite of 11 sam ples collected from the Tasigake alkali granite pluton, Ulungur River regio n, northern Xinjiang. Istopic exchange with meteoric water during subsolidu s cooling caused strong O-18-D depletion and the remarkable nonequilibrium O-18/O-16 relation between coexistent minerals. O-18/O-16 exchange kinetic effects of the three minerals are simultaneously and consistently modelled. Exsolution and microtextural reorganization of alkali feldspar, and infilt ration of water have been mutually facilitated by each other. Shallow Intru sion, and circulation of meteoric water throughout the pluton cool it effec tively. As a result, the "heat engine" is rapidly extinguished, and the non equilibrium O-18/O-16 relation is frosen.