Oxygen Isotope Exchange Kinetics Between Coexistent Minerals And Water In Some Granite Plutons Of The Altay Mountains

In this Ph. D thesis the author performed a systematic research on the oxygen isotope exchange kinetics between external water and coexistent mineral triplets quartz,feldspar,biotite or arfvedsonite from three granite plutons Aral,Ertaibei,and Saertielieke,selected from northern Xinjiang. Coexistent quartz and feldspar separates of 11 rock samples,from the main body of the Aral pluton,and of 11 rock samples,from the Ertaibei pluton,manifest negative AOQuanz-Feidspar values,which could be attributed to the 18O/16O exchange with 18O-enriched water during subsolidus cooling. Derivation of the 18O-enriched fluids was either related to the thrusting of the Ertish thrust zone,or,to the dehydration in the lower crust caused by the underplating or,alternatively,induced by adjustment in the lithospheric thermal structure. Fluid systems associated with emplacement of the Aral and Ertaibei plutons derived from the magma source regions,accompanied the magma body in ascendence,and encircled the plutons as an envelope.The quantitative modelling gives a relatively higher relative rate constant kAikaii-feidspar/kQuaitz and a relatively longer time-duration kquaitzt of exchange for samples of the phenocrystic medium-grained rocks as compared with those of the fine-grained rocks,in the Saertielieke alkali granite pluton. Exsolution and microtextural reorganization of alkali feldspar,and infiltration of meteoric water and the accompanying 18O/16O exchange must have been mutually facilitated by each other during slow cooling. Two modes can be recognized for the arfvedsonite-meteoric water interactions:1) two stage model of mixing plus isotopic exchange;2) D/H and 18O/16O exchange between arfvedsonite and meteoric water.