Data for Grain Growth in Olivine + Ferropericlase Rocks Deformed to High Strains

Abstract

We performed grain growth experiments on four samples of olivine (Ol) + periclase (Per); three samples contained volume fractions of fPer = 0.2, 0.5, 0.8 of Per100 while the fourth contained fPer = 0.2 of Per70, a Fe-bearing periclase. Prior to the grain growth experiments, these samples were deformed to shear strains of γ = 6 – 7, which resulted in a well-mixed, random distribution of grains of both phases among each other. After deformation, samples were statically annealed for 10 h and 100 h at T = 1523 K in a one-atmosphere furnace to facilitate grain growth. Almost all grain growth occurred within the first 10 h of annealing and only the sample containing fPer = 0.8 experienced additional, albeit limited, grain growth up to 100 h. Additionally, grain growth laws determined for single-phase samples of Ol and Per predict increases in grain size by factors of 4 and 5, respectively after 100 h of annealing, larger than observed in our experiments. We attribute the initial increase in grain size during the first 10 h of annealing to stored strain energy from deformation and/or Ostwald ripening, however the kinetics of grain growth are too slow in our samples to allow for grain growth over longer periods of time. The lack of significant grain growth in our study reaffirms the importance of Zener pinning in polymineralic rocks deformed to large strains, such that, once mixing is thorough, pinning along interphase boundaries is effective at maintaining a fine grain size.