Creating Calibration Curves using In Situ X-ray Diffraction to Determine the Shock Pressure Experienced by Clinopyroxene
Abstract
This work extends on two quantitative methods for evaluating shock metamorphism to include clinopyroxene using X-ray diffraction (XRD). Clinopyroxene samples experimentally shocked to known shock pressures were studied with XRD. Lattice strain (ε) and strain-related mosaicity (SRM) were measured for each sample and plotted against their known shock pressures, creating a ε versus shock pressure calibration curve and an SRM versus shock pressure calibration curve. These calibration curves were applied to three meteorites: Nakhla, Zagami, and ALHA 77005. The SRM calibration curve gave peak shock pressures of 12±8 GPa for Nakhla, 44±8 GPa for Zagami, and 68±8 GPa for ALHA 77005. The SRM calibration curve is inaccurate because high SRM values weren’t adequately sampled. The ε calibration curve gave peak shock pressures of 8±12 GPa for Nakhla, 36±12 GPa for Zagami, and 90±12 GPa for ALHA 77005. The ε calibration curve is effective when sufficient amounts of data are used.