Coefficients were determined for diffusion parallel to each of the 3 crystallographic directions in natural orthoenstatite. Experiments were conducted at 1atm in CO-CO2 gas. The 25Mg was introduced into polished samples of oriented orthoenstatite by using a film of isotopically enriched 25MgO as the source. Penetration profiles were measured using an ion microprobe. The diffusion at 900, 850, 800 and 750C was described by:

a-axis:     D(m2/s) = 1.10 x 10-4 exp[-360(kJ/mol)/RT]

b-axis:    D(m2/s) = 6.93 x 10-6 exp[-339(kJ/mol)/RT]

c-axis:     D(m2/s) = 4.34 x 10-9 exp[-265(kJ/mol)/RT]

C.S.Schwandt, R.T.Cygan, H.R.Westrich: Contributions to Mineralogy and Petrology, 1998, 130[3-4], 390-6