Variability of diffusion of argon in albite, pyroxene, and olivine in shocked and unshocked samples

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 ∼30-60 GPa all have an equal effect on the diffusion parameters, lowering the activation energy (E) from ∼45 to ∼25 kcal/mol, and the log D0/a2 from ∼4 to ∼1 s−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 ∼80 kcal/mol, and the log D0/a2 from ∼14 to ∼7 s−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 ∼100 kcal/mol and a log D0/a2 of ∼10 s−1, intermediate to the values of mixed pyroxene when shocked and unshocked. The olivine (Fa18) has an E of ∼45 kcal/mol and a log D0/a2 of ∼1 s−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).