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Contributions to Mineralogy and Petrology

, Volume 134, Issue 2–3, pp 251–263 | Cite as

An empirical model for the calculation of spinel-melt equilibria in mafic igneous systems at atmospheric pressure: 2. Fe-Ti oxides

  • Alexi A. Ariskin
  • Galina S. Barmina
Article

Abstract

In order to develop models simulating the crystallization of Fe-Ti oxides in natural lavas, we have processed published experimental data on magnetite-melt and ilmenite-melt equilibria. These data include 62 Mt-melt and 75 Ilm-melt pairs at temperatures 1040–1150 °C, oxygen fugacities from IW to NNO+2, and bulk compositions ranging from ferrobasalts to andesites and dacites. Five major cations (Fe3+, Fe2+, Ti4+, Mg2+ and Al3+) were considered for the purpose of describing Fe-Ti oxide saturation as a function of melt composition, temperature and oxygen fugacity at 1 atmosphere pressure. The empirically calibrated mineral-melt expression based on multiple linear regressions is: ln D i = a/T + blog fO2 + c + d1XNa + d2XK + d3XP, where D i represents molar distribution coefficients of the given cations between Mt/Ilm and melt; XNa, XK, and XP are the molar fractions of Na, K, and P in the melt. The empirically calibrated Mt-melt and Ilm-melt equilibria equations allowed us to develop two models for calculating crystallization temperatures of the Fe-Ti oxides in the melts with an accuracy of 10–15 °C, and compositions with an accuracy of 0.5–2 mol%. These models have been integrated into the COMAGMAT-3.5 program, improving our ability to study numerically the effects of temperature and oxygen fugacity on the stability and phase equilibria of Fe-Ti oxides. Application of this approach to the tholeiitic series of Chazhma Sill from Eastern Kamchatka (Russia) indicates oxygen fugacity conditions near NNO + 0.5. Numerical simulation of fractional crystallization of an iron-enriched basaltic andesite parent at these oxidizing conditions accurately reproduces the FeO-SiO2 relations observed in the Chazhma suite.

Keywords

Magnetite Olivine Ilmenite Oxygen Fugacity Contrib Mineral Petrol 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Alexi A. Ariskin
    • 1
  • Galina S. Barmina
    • 1
  1. 1.Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Kosygin st. 19, Moscow, 117975, Russia Fax: (095) 938-2054, e-mail: ariskin@glas.apc.orgRussia

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