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 1100degreesC, 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 mm. The data are well fit by a single piezometer relation, D = 10(3.56+/-0.27) * sigma(-1.26+/-0.13), with no change in slope at the regime 2-3 transition and no effect of temperature or alpha/beta 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.