Molybdenum Solubility in Silicate Melt at High Pressures and Temperatures: Experimental Constraints on Planetary Core Formation

摘要: Introduction: We present here data from more than sixty experiments on molybdenum (Mo) solubility in a wide range of silicate melt compositions at pressures 0.5 to 11.5 GPa and temperatures 1360 2080°C. The purpose this study is determine if there are conditions during core formation that can explain the Mo abundance Earth’s upper mantle mantles Moon Mars. refractory, moderately siderophile element should be terrestrial planets with little or no depletion due accretionary volatility effects. Hence planetary bulk expected “chondritic” partitioned solely between crust+mante metallic differentiation. Based estimates content Earth [1,2] partition coefficient for DMo (metal/silicate) = 50-80 would consistent equilibrium core-mantle segregation. Interestingly, earlier experimental work done 1-atm modest report 10-10, depending oxygen fugacity, valence state, structure expressed as non-bridging oxygens divided by tetrahedrally coordinated cations (NBO/T) (see [3] overview partitioning behavior). an apparent excess based low pressure data, similar observed other elements such W, Ni, Co. Experimental studies [46] have shown “excess” Ni Co explained high temperature core-forming magma ocean negative dependence DNi DCo. Therefore we seek uncover which factors stage evolution could contributed distribution Mo. Elucidating effects P, T, X, fO2 etc. combining themwith existing P-T Co, V, Cr further constrain depths planets. Experimental: presented piston-cylinder multi-anvil run Agee High-Pressure Laboratory over course last fifteen years. include komatiite, peridotite, komatiite-fayalite mixtures, hydrous lunar green glass, black glass. All were saturated (Mo-Fe capsules) was fixed exchange MoMoO3 Fe-FeO metal capsule melt. Liquidus super-liquidus existed all experiments. Concentration levels MoO3 determined electron microprobe analyses ranged minimum 0.07 wt% glass 1360°C maximum 6.97 mixture 8 1750°C. Effects Melt Composition: There appears very strong effect increasing P T along Apollo 14 Black Glass liquidus (figure 1). This agreement previous [7] although D-values much lower composition under 1415-2080°C 1.0-11.5 GPa.