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A Subgrain-Size Piezometer Calibrated for EBSD
We calibrate a subgrain-size piezometer using electron backscatter diffraction (EBSD) data collected from experimentally deformed samples of olivine and quartz. Systematic analyses of angular and spatial resolution test the suitability of each dataset for inclusion in calibration of the subgrain-size piezometer. To identify subgrain boundaries, we consider a range of critical misorientation angles and conclude that a 1° threshold provides the optimal piezometric calibration. The mean line-intercept length, equivalent to the subgrain-size, is found to be inversely proportional to the von Mises equivalent stress for datasets both with and without the correction of Holyoke and Kronenberg (2010). These new piezometers provide stress estimates from EBSD analyses of polymineralic rocks without the need to discriminate between relict and recrystallised grains and therefore greatly increase the range of rocks that may be used to constrain geodynamic models.This research was supported by the NERC Environmental Research DTP grant NE/L002612/1, University of Oxford, RMG, and National Science Foundation (NSF) Awards EAR-1755805 to DLK, EAR-1806791 to KMK and EAR-1848380 to CWH. Qz-2 experiments were performed by CWH with support from NSF grants EAR-0208150 to Jan Tullis and EAR-1321882 to CWH and Andreas K. Kronenberg. In addition, DW acknowledges support from the Netherlands Organisation for Scientific Research, User Support Programme Space Research, grant ALWGO.2018.038