Micro X-Ray Diffraction Observations and Calibration of Experimentally Shocked Plagioclase Feldspars: Comparison With Raman Spectroscopic Observations

Plagioclase feldspar is a ubiquitous mineral found in planetary bodies such as Earth, Moon, Mars, large igneous asteroids such as Vesta, numerous achondrites, and every class of chondritic meteorite. Because all solid planetary bodies are potentially subject to hypervelocity impacts, understanding the shock response of plagioclase enables a better understanding of the geological histories of planetary bodies. This study investigates the response of andesine and bytownite to high-pressure shock waves using micro-XRD and Raman. Fourteen andesine and 11 bytownite samples, which had been previously shocked to peak pressures of 0–56 GPa, were examined. Micro-XRD revealed characteristic signatures of shock damage, including weakened diffraction intensities and heightened background signal, reflecting structural collapse under high pressures. Andesine-bearing rock showed the onset of amorphization at 28.4–29.6 GPa, progressing to complete amorphization at 47.5–50 GPa. Bytownite-bearing rock displayed a similar trend but with higher pressure thresholds: partial amorphization occurred at 25.5–27.0 GPa, and complete amorphization at 38.2–49 GPa. To quantify the degree of shock experienced by plagioclase minerals, we measured the Full Width at Half Maximum (FWHMχ) of Debye rings (from 2D XRD images) for samples across different shock levels. We established linear regression models between ΣFWHMχ and peak shock pressure for both andesine (0–28.4 GPa) and bytownite (0–25.5 GPa) using data from samples that remained crystalline. The model is particularly effective for low shock levels, while Raman is more effective at higher shock pressures. These quantitative relationships provide a valuable tool for assessing the shock history recorded in plagioclase minerals.