Metal size distributions in EH and EL chondrites

Abstract

EL chondrites exhibit larger average metal grain sizes than EH chondrites, a difference attributed by Easton [1983] to metamorphic coarsening, as most EL chondrites are equilibrated, and most EH chondrites are unequilibrated. In this paper, we present metal grain size data for three unequilbrated EL3 chondrites (PCA 91020; ALH 85119; MAC 88180) , and three EH3 chondrites (ALH 84170; PCA 91085; PCA 91238). We find that EL3 chondrites have larger average metal grain sizes than EH3 chondrites, and that grain sizes of the unequilibrated enstatite chondrites are similar to those of equilibrated chondrites of the same class. We thus interpret the metal size distributions of enstatite chondrites as primarily reflecting their pre‐metamorphic distributions. Shock processing appears to have had only minor influence on metal grain size distributions in these meteorites.