OXYGEN DIFFUSION IN ANHYDROUS SANIDINE FELDSPAR

Oxygen exchange experiments have been performed between single crystal s of sanidine feldspar and oxygen gas enriched in O-18, at temperature s in the range 869-1053 degrees C, total pressure 1 atmosphere, for ti mes up to 28 days. Oxygen isotope diffusion profiles in a direction pe rpendicular to (001) were determined with an ion microprobe. The exper imental data obey a single Arrhenius relationship of the form D = 8.4 x 10(-11) exp. (-245 +/- 15 kJ mol(-1)/RT) m(2)s(-1). The results indi cate that oxygen diffusion in anhydrous sanidine feldspar is marginall y slower than oxygen diffusion in anhydrous anorthite. Comparison with published atomistic simulation studies suggests that oxygen transport in feldspar is by an interstitial mechanism.