We analyzed the argon diffusion parameters of albite and pyroxene as a function of shock, as well as an olivine of unknown shock pressure. In albite, shock pressures of ~30-60GPa all have an equal effect on the diffusion parameters, lowering the activation energy (E) from ~45 to ~25kcal/mol, and the logD 0/a 2 from ~4 to ~1s -1. In a mixture of low-Ca and high-Ca pyroxene, similar shock pressures also have an equal effect, lowering the E from ~130 to ~80kcal/mol, and the logD 0/a 2 from ~14 to ~7s -1. However, given that some shocked and unshocked pyroxene splits have similar release patterns, making a clear distinction between the two is difficult. Additionally, splits of pure unshocked high-Ca pyroxene have an E of ~100kcal/mol and a logD 0/a 2 of ~10s -1, intermediate to the values of mixed pyroxene when shocked and unshocked. The olivine (Fa 18) has an E of ~45kcal/mol and a logD 0/a 2 of ~1s -1, somewhat similar to that of feldspar. These results will be useful in interpreting complex argon release patterns from shocked multi-mineral samples too fine-grained for easy mineral separation (such as chondrites).
ASJC Scopus subject areas
- Geochemistry and Petrology