Fe2+–Mg partitioning between olivine and liquid at low oxygen fugacity: an experimental and thermodynamic framework

Abstract A set of 1-atm gas-mixing experiments ( n = 31) was run using Re wire loops at low-oxygen fugacity (ƒO 2 , within one half-log unit the Fe–FeO buffer) and temperatures 1175–1400 °C to explore compositional dependence Fe 2+ –Mg olivine–liquid exchange coefficient, $${\mathrm{K}}_{\mathrm{D},{\mathrm{Fe}}^{2+}-\mathrm{Mg}}^{\mathrm{ol}/\mathrm{liq}}$$ K D , Fe 2 + - Mg ol / liq under conditions where corrections for liquid 3+ are small. The bulk compositions used these include a picrite, high-alumina basalt, suite three MORB with variable Fe/Mg. values from 14 on pre-saturated were fit regular solution model that relates temperature, melt composition, olivine composition. in is well-described two parameters: SiO content coexisting Combining our literature compilation low-pressure, low-ƒO (largely non-terrestrial compositions) produced combined data spanning broad region composition space (e.g., TiO Na O + K contents up 18.4 wt% 8.4 wt%, respectively). Fitting this expanded experimental database required additional terms: Ti, Si-(Na K) cross-term. Because all liquids low, variation seen effectively independent effects /Fe ratios. Given Mg or partition coefficient information, it possible eliminate explicit enabling simple iterative approach calculating given only (and ratio) an olivine-saturated liquid.