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TitlePartitioning coefficients between olivine and silicate melts
AuthorBédard, J H
SourceModelling of magma chambers - in honour of J.C. Duchesne; by Vander Auwera, J (ed.); Lithos vol. 83, issue 3-4, 2005 p. 394-419,
LinksSupplementary Data - Données supplémentaires
Alt SeriesGeological Survey of Canada, Contribution Series 2004105
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
Subjectstectonics; igneous and metamorphic petrology; partial melting; magmas; olivine; petrogenesis; modelling; trace elements; silicates; fractional crystallization; pressure-temperature conditions; forsterite; oxides; scandium; yttrium; trace element analyses; basalts; equilibrium; anomalies; tantalum; hafnium; zirconium; titanium; niobium; electron probe analyses; statistical analyses; partitioning; Nernst partition coefficients; water content; rare earth elements; large ion lithophile elements; Lattice Strain Model; kinetic effects
Illustrationstables; plots; models
AbstractVariation of Nernst partition coefficients (D) between olivine and silicate melts cannot be neglected when modeling partial melting and fractional crystallization. Published natural and experimental olivine/liquidD data were examined for covariation with pressure, temperature, olivine forsterite content, and melt SiO2, H2O, MgO and MgO/MgO + FeOtotal. Values of olivine/liquidD generally increase with decreasing temperature and melt MgO content, and with increasing melt SiO2 content, but generally show poor correlations with other variables. Multi-element olivine/liquidD profiles calculated from regressions of D REE-Sc-Y vs. melt MgO content are compared to results of the Lattice Strain Model to link melt MgO and: D0 (the strain compensated partition coefficient), EM3+ (Young's Modulus), and r0 (the size of the M site). Ln D0 varies linearly with Ln MgO in the melt; EM3+ varies linearly with melt MgO, with a dog-leg at ca. 1.5% MgO; and r0 remains constant at 0.807 Å. These equations are then used to calculate olivine/liquidD for these elements using the Lattice Strain Model. These empirical parameterizations of olivine/liquidD variations yield results comparable to experimental or natural partitioning data, and can easily be integrated into existing trace element modeling algorithms. The olivine/liquidD data suggest that basaltic melts in equilibrium with pure olivine may acquire small negative Ta-Hf-Zr-Ti anomalies, but that negative Nb anomalies are unlikely to develop. Misfits between results of the Lattice Strain Model and most light rare earth and large ion lithophile partitioning data suggest that kinetic effects may limit the lower value of D for extremely incompatible elements in natural situations characterized by high cooling/crystallization rates.

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