Shock Veins in Meteorites: What They Tell Us About Shock Conditions

Abstract

The goal of classifying the shock metamorphic features in meteorites is to estimate the corresponding shock pressure conditions [1]. However, the temperature variability of shock metamorphism is equally important and can result in diverse shock features in samples with equilibrated pressures. Shock-melt veins and melt pockets correspond to the highest temperatures in shock meteorites and they are the location of high-pressure (HP) minerals [2]. The usefulness of shock veins for interpreting shock conditions is debated. Stoeffler et al [3] suggest that shock veins do not provide useful estimates of shock pressure because they represent large deviations from average shock effects. However, these features provide an important mineralogical and chemical record of shock history [4]. Fritz et al. [5] claim that shock veins and HP minerals only record peak shock pressure in the isobaric zone for low-velocity (~ 2km/s) impacts, such as that recorded in L chondrites. Although other shocked materials may not sample the isobaric zone, their crystallization history is still useful for understanding the shock history. Here we calculate shock-temperatures and quench paths to semi-quantitatively evaluate the relationship between shock-melt crystallization and shock pressure.

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