MnO exsolution in periclase from Långban, Sweden: An evaluation of the activity-composition relations in the system MgO-MnO

J. P R De Vllliers, P R Buseck, H. S. Steyn

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

The occurrence of MnO exsolution in periclase host crystals from Långban, Sweden is described. The composition of the periclase is Mg0.942 Mn0.046Zn0.012O, and it coexists with exsolved manganosite crystals with a composition of Mn0.909Mg0.082Zn0.008O. Crystals of hausmannite are also present, indicating fo2 conditions approaching the MnO-Mn3O4 equilibrium. Activity-composition data for the system MgO-MnO is critically reviewed. The data obtained from solid electrolyte measurements are rejected because of the unrealistic calculated equilibration temperatures and the large deviations from the gas equilibration Mn-Pt activity measurements. The large errors associated with the gas equilibration measurements, especially at large XMnO, also introduces uncertainties associated with the asymmetric interaction parameters. The non-parametric 'jack-knife' method was used to determine the asymmetric interaction parameters and their standard deviations from the data of Wood et al. (1994) and Tsai and Muan (1992). These were calculated as WMno = 21.2 kJ/mol, σWMno = 2.5 kJ/mol and WMgO = 8.2 kJ/mol, σWMgo = 3.3 kJ/mol. Ushig the asymmetric interaction parameters, WMnO = 19.9 kJ/mol and WMgo = 13.7 kJ/mol for the system MgO-MnO as determined by Wood e, al. (1994) and the equations for two-phase equilibrium as formulated by Thompson (1967), equilibration temperatures of 334°C and 466°C were calculated. The difference between the calculated temperatures is ascribed to inaccuracies in the experimentally determined interaction parameters.

Original languageEnglish (US)
Pages (from-to)333-339
Number of pages7
JournalMineralogical Magazine
Volume62A
Issue numberPART 3
DOIs
StatePublished - Jan 1 1998

Keywords

  • Calculated solvus
  • Exsolution
  • Manganosite
  • Periclase
  • System MgO-MnO

ASJC Scopus subject areas

  • Geochemistry and Petrology

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