Stoichiometry of the iron oxidation reaction in silicate melts

Journal Article · · American Mineralogist; (USA)

OSTI ID:7188975

Kress, V C; Carmichael, I S.E. ^[1]

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1. Univ. of California, Berkeley (USA)

Experiments have been performed that calibrate the stoichiometry and thermodynamics of the iron oxidation reaction in natural silicate melts. A series of experiments was carried out on six melt compositions covering a far larger range of oxygen fugacities than had been examined previously. Oxygen fugacities between air and 5.2 log{sub 10} units below those defined by the nickel-nickel oxide assemblage were investigated at 1360 C and 1460 C. Results of these experiments confirm that ln(X{sub Fe{sub 2}O{sub 3}}/X{sub FeO}) is a linear function of ln {line integral}{sub O{sub 2}} over this entire range, and that this linear behavior is independent of composition over the range considered. These results are inconsistent with an ideal mixing between FeO and Fe{sub 2}O{sub 3} components. They are, however, entirely consistent with ideal mixing between FeO and FeO{sub 1.464{plus minus}0.003} (FeO 6Fe{sub 2}O{sub 3}) components. A second series of experiments was performed on a single mid-ocean ridge basalt composition (JDFD2) in order to better constrain the temperature dependence of the iron oxidation reaction in this simplified two-component subsystem. This series was carried out at temperatures between 1299 C and 1636 C in air, CO{sub 2}, and 0.2 log{sub 10} units below the fayalite-magnetitie-quartz buffer assemblage. Results of both series of experiments were combined with the Sack et. al. (1980) and Kilinc et al. (1983) databases to estimate thermodynamic parameters for the iron oxidation reaction expressed in terms of FeO and FeO{sub 1.464} components. These coefficients offer the most precise method available for estimation of iron oxidation state in natural silicate melts as a function of ln {line integral}{sub O{sub 2}}, temperature, and composition.

• OSTI ID: 7188975
• Journal Information: American Mineralogist; (USA), Journal Name: American Mineralogist; (USA) Vol. 73:11-12; ISSN AMMIA; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
BASALT
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
ELEMENTS
EQUILIBRIUM
GEOCHEMISTRY
IGNEOUS ROCKS
IRON
IRON COMPOUNDS
IRON OXIDES
LOSSES
MAGMA
METALS
NICKEL
NICKEL COMPOUNDS
NICKEL OXIDES
NONMETALS
OXIDATION
OXIDES
OXYGEN
OXYGEN COMPOUNDS
ROCKS
SILICATES
SILICON COMPOUNDS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
THERMODYNAMICS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VOLCANIC ROCKS