Olivine-liquid equilibria and the chemical activities of FeO, NiO, Fe sub 2 O sub 3 , and MgO in natural basic melts

Journal Article · Wed Jan 01 00:00:00 EST 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90135-6· OSTI ID:5035684

Snyder, D A; Carmichael, I S.E. ^[1]

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1. Univ. of California, Berkeley (United States)

The distribution of the cations Fe{sup +2}, Mg{sup +2}, Ni{sup +2}, Mn{sup +2}, and Ca{sup +2} between olivine and natural basic liquid is experimentally explored at one atmosphere as functions of oxygen fugacity, temperature, and composition. By performing the experiments in equilibrium with NiFe alloys, the chemical activities of FeO, Fe{sub 2}O{sub 3}, and Ni{sub O} were monitored in the melt and from knowledge of the thermodynamics of olivine mixing, the activity of MgO was also calculated. This is the first time that the activity of Fe{sub 2}O{sub 3} has been monitored in a natural melt and also the first observations of the variation of a{sub FeO} with oxygen fugacity. Empirical models for the variation of the activities of these components as functions of oxygen fugacity, temperature, and composition are presented and the models for FeO and MgO are shown to be able to predict the olivine composition. The partition coefficients for FeO, MgO, NiO, and MnO for olivine were found to be invariant over more than 9 orders of magnitude in oxygen fugacity. The calcium partition coefficient decreases with increasing f{sub o{sub 2}}, but this is due to the changing olivine composition with oxygen fugacity. Nickel, manganese, and calcium partitioning are functions of composition and temperature, although thermodynamic analysis shows that the temperature variation for NiO and MnO is primarily due to the temperature dependence of the activity coefficients rather than a large enthalpy of the exchange reactions. Empirical predictive models are presented for the partition coefficients of all of the divalent cations.

• OSTI ID: 5035684
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 56:1; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
58 GEOSCIENCES
IRON OXIDES
ACTIVATION ENERGY
DISTRIBUTION
MAGMA
PHASE STUDIES
MAGNESIUM OXIDES
NICKEL OXIDES
CHEMICAL COMPOSITION
ELECTRON MICROPROBE ANALYSIS
EQUILIBRIUM
EXPERIMENTAL DATA
GEOCHEMISTRY
MANGANESE OXIDES
OLIVINE
OXYGEN
PARTITION FUNCTIONS
QUANTITY RATIO
RESERVOIR TEMPERATURE
THERMODYNAMIC PROPERTIES
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMISTRY
DATA
ELEMENTS
ENERGY
FUNCTIONS
INFORMATION
IRON COMPOUNDS
MAGNESIUM COMPOUNDS
MANGANESE COMPOUNDS
MICROANALYSIS
MINERALS
NICKEL COMPOUNDS
NONDESTRUCTIVE ANALYSIS
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATE MINERALS
TRANSITION ELEMENT COMPOUNDS
152002* - Geothermal Data & Theory- Properties of Minerals & Rocks
580000 - Geosciences