Oxygen diffusion rates in quartz exchanged with CO2

摘要: Oxygen self diffusion rates were determined in quartz samples exchanged with18O-enriched CO2 between 745 and 900°C various pressures, the profiles measured using an ion microprobe. The activation energy (Q) preexponential factor (D0) at P(CO2) = P(tot) 100 bar, for parallel to c-axis are 159 ( ± 13) kJ/g atom 2.10 (+0.75/ −0.55) × 10−8 cm2/s. This rate is approximately times slower than that obtained from hydrothermal experiments faster a previous 1-bar quartz-O2 exchange experiment. oxygen 0.6 888°C, vacuum agreement with with18O2. effect of higher pressures small. At 900°C, 2.35 10−15 cm2/s 2.24 3.45 kbar 8.13 7.2 kbar. There probably diffusing species, other oxygen, enhances these quartz-CO2 systems, relative occurring very low or vacuum. this however, not as strong associated H2O. Preserved isotope fractionations coexisting minerals slowly cooled, high-grade metamorphic terrane will vary depending upon whether water-rich phase was present not. Closure temperatures be 100°C rocks where no during cooling. may potentially used sensor water presence retrogression.