The recrystallized grain size piezometer for quartz

In order to determine a recrystallized grain size piezometer for quartz, we deformed Black Hills quartzite in a molten salt assembly in a Griggs apparatus at 1.5 GPa, 800 to 1100°C, and strain rates between 2*10 −7 and 2*10 −4 s −1 , conditions which include dislocation creep regimes 2 and 3 of Hirth and Tullis [1992] . Flow stresses ranged from 34 ± 16 to 268 ± 38 MPa with corresponding recrystallized grain sizes from 46 ± 15 to 3.2 ± 0.7 μm. The data are well fit by a single piezometer relation, D = 10 3.56± 0.27 * σ −1.26 ± 0.13 , with no change in slope at the regime 2–3 transition and no effect of temperature or α/β stability field. Another experimental piezometer relation for regime 1 of Hirth and Tullis [1992] differs in slope, suggesting that different recrystallization mechanisms require different piezometer calibrations.