Influence of oxygen fugacity and temperature on the redox state of iron in natural silicic aluminosilicate meltsстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The influence of oxygen fugacity (fO(2)) and temperature on the valence and structural state of iron was experimentally studied in glasses quenched from natural aluminosilicate melts of granite and pantellerite compositions exposed to various T-fO(2) conditions (1100-1420A degrees C and 10(-12)-10(-0.68) bar) at a total pressure of 1 atm. The quenched glasses were investigated by Mossbauer spectroscopy. It was shown that the effect of oxygen fugacity on the redox state of iron at 1320-1420A degrees C can be described by the equation log(Fe3+/Fe2+) = k log(fO(2)) + q, where k and q are constants depending on melt composition and temperature. The Fe3+/Fe2+ ratio decreases with decreasing fO(2) (T = const) and increasing temperature (fO(2) = const). The structural state of Fe3+ depends on the degree of iron oxidation. With increasing Fe3+/Fe2+ a parts per thousand yen 1, the dominant coordination of Fe3+ changes from octahedral to tetrahedral. Ferrous iron ions occur in octahedral (and/or five-coordinated) sites independent of Fe3+/Fe2+.