The Mg/2+/-Fe/2+/ order-disorder and the thermodynamics of the orthopyroxene, /Mg,Fe/2Si2O6 crystalline solution. Part 1 - A Fe 57 Moessbauer resonance study of the Mg/2+/-Fe/2+/ distribution in orthopyroxenes at 500, 600, 700 and 800 C

Iron 57 Mossbauer resonance determination of distribution isotherms for bibalent Mg and Fe ions between M1 and M2 sites in orthopyroxene