Cation diffusion in olivine—II. Ni-Mg,Mn-Mg,Mg and Ca |
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| Authors: | Masana Morioka |
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| Institution: | Radioisotope Centre, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, 113 Japan |
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| Abstract: | Diffusivities of bivalent cations. Mg, Ni. Mn and Ca, in olivine were determined experimentally. The diffusivities of Ni and Mn in forsterite were determined by couple annealing between Ni2SiO4 and Mg2SiO4, and Mn2SiO4 and Mg2SiO4, respectively. The diffusivities of Mg and Ca in forsterite were determined by the use of 26Mg and Ca tracers, respectively. Combined with other published results, the diffusion coefficients for bivalent cation diffusion in pure forsterite along the c crystallographic axis range from 2.45 × 10?11 to 1.4 × 10?13 cm2 sec?1 at 1200°C, in the order of Fe > Mn > Co > Ni > Mg > Ca. The results suggest that the diffusivity is governed by at least two factors, i.e. the size of the diffusing ionic species and the change of defect density in the crystal structure which is induced by substitution of diffusing ion for Mg ion. |
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