Thermodynamic formulations of (Ca,Fe,Mg)2SiO4 olivine.

• KAWASAKI Toshisuke

  Division of Earth Sciences, Department of Biosphere-Geosphere Sciences, Faculty of Science, Ehime University

Abstract

The multi-site regular solution model is applied to the intracrystalline exchange reaction of Fe²⁺ and Mg²⁺ between M1 and M2 sites of olivine. Effects of Ca on the Fe–Mg intracrystalline distribution coefficient K_D[=(X_Mg^M2X_Fe^M1)⁄(X_Fe^M2X_Mg^M1] are derived from this solution model, which indicates that Fe preferentially orders onto the lager M2 site accompanying with increasing Ca. This reaction would be assumed to be temperature-independent. The difference between Fe–Mg mixing parameters of M1 and M2 sites is very small and temperature-independent, so that the fayalite-forsterite olivine would be approximated as a binary regular solution.<BR>The miscibility gaps between high-Ca and low-Ca olivines are sufficiently described by the disordered multi-site regular solution model, which is very similar to a symmetric regular solution model. The present estimates for Margules parameters W_MgCa^M2 is consistent with Davidson and Mukhopadhyay’s (1984) analysis of miscibility gap in Ca–Fe–Mg olivines, and is slightly less non-ideal than the Adams and Bishop’s (1985) results estimated from the mon-ticellite-forsterite solvus. The Ca–Fe mixing is more non-ideal than the previous estimates.

Journal

• Mineralogical Journal

  Mineralogical Journal 20 (3), 135-149, 1998

  Japan Association of Mineralogical Sciences

Keywords

• General Earth and Planetary Sciences
• General Environmental Science

Details

• CRID: 1390001206546477056
• NII Article ID: 10008773224
• NII Article ID: 30027161523
• NII Book ID: AA00739590
• DOI: 10.2465/minerj.20.135
• ISSN: 18814174
• ISSN: 05442540
• ISSN: http://id.crossref.org/issn/05442540
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed