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 data set 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 data sets both with and without the correction of Holyoke and Kronenberg (2010, https://doi.org/10.1016/j.tecto.2010.08.001). These new piezometers provide stress estimates from EBSD analyses of polymineralic rocks without the need to discriminate between relict and recrystallized grains and therefore greatly increase the range of rocks that may be used to constrain geodynamic models.
Bibliographical noteFunding Information:
The authors thank Andrew Cross for useful discussions. Jon Wade and Phillip Gopon are gratefully acknowledged for technical support on the SEM. We thank Luca Menegon and Phil Skemer for insightful reviews and Steve Jacobsen for editorial handling. This research was supported by the NERC Environmental Research DTP grant NE/L002612/1, University of Oxford, R.M.G, and National Science Foundation (NSF) Awards EAR‐1755805 to D. L. K., EAR‐1806791 to K. M. K., and EAR‐1848380 to C. W. H. Qz‐2 experiments were performed by C.W.H with support from NSF Grants EAR‐0208150 to Jan Tullis and EAR‐1321882 to C. W. H. 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.
© 2020. The Authors.