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Mineral-melt partitioning of redox-sensitive elements
  • Antony D Burnham,
  • Guil Mallmann,
  • Raul O C Fonseca
Antony D Burnham
Australian National University

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Guil Mallmann
Australian National University
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Raul O C Fonseca
Ruhr-University Bochum
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Elements with variable valence state (i.e. redox-sensitive) often show contrasting mineral/melt partition coefficients as a function of oxygen fugacity (fO2) in magmatic systems. This is because trace-element incorporation into crystal lattices depends on the charge, size, and crystal-field stabilization energy of atoms, all of which differ greatly between oxidized and reduced species of the same element. This has two critical implications: (1) petrologic/ geochemical modelling of partitioning behavior of redox-sensitive trace-elements in magmatic systems requires some knowledge of their oxidation state, and (2) the oxidation state of magmatic systems may be inferred from partitioning relations of redox-sensitive trace elements preserved in mineral and melt phases of rapidly cooled magmas. The advantage of this oxybarometric approach is that mineral/melt partitioning relations are not sensitive to late stage degassing, charge-transfer on quenching, or surficial alteration. In this chapter we discuss the theoretical treatment of experimental mineral/melt partitioning data of redox-sensitive trace elements, and review aspects concerning the partitioning behavior of well-known redox-sensitive elements, including transition metals (Ti, V, Cr, Fe), rare earth elements (Ce, Eu), U, and siderophile elements (Mo, W, Re, and platinum group elements) under planetary magmatic fO2 conditions.
30 Sep 2021Published in Magma Redox Geochemistry on pages 345-367. 10.1002/9781119473206.ch17