The influence of pressure and temperature on the metal-silicate partition coefficients of nickel and cobalt in a model C1 chondrite and implications for metal segregation in a deep magma ocean

Conditions of core formation in the earth: Constraints from Nickel and Cobalt partitioning

“…At 7 GPa, both D(Ni) and D(Co) decrease with increasing temperature, though the effect is more pronounced for Ni than for Co. The observed decrease in D(Ni) and D(Co) with increasing temperature is generally consistent with the previous oneatmosphere studies of Capobianco and Amelin (1994) and Holzheid and Palme (1996), which each covered a temperature range of Ͻ300 K. At pressures above one-atmosphere, Thibault and Walter (1995) conducted experiments at 5 GPa and three different temperatures, over a total range of 450 K; Li and Agee (2001) also ran experiments at three different temperatures, with a smaller overall range of 350 K, at 10 GPa. Though limited to essentially three points and a small range in temperature to constrain the slopes, both of these studies suggested some decrease in D(Ni) and D(Co) with increasing temperature, consistent with our new result in Figure 3.…”

“…To achieve good separation of the metal and silicate phases, lower temperature runs #Ni20, #Ni24, and #Ni25 were first raised to 2273 K for 2 min and then lowered to their run temperatures. The choices of run durations were based on previous multi-anvil experimental studies that demonstrated that equilibrium was obtained during such run durations (Thibault and Walter, 1995;Gessmann and Rubie, 1998;Li and Agee, 2001;. The experiments #Ni20 and #Ni24, both conducted at 1973 K, gave consistent partitioning results despite the different run durations of 3 hours and 1 h respectively, suggesting that equilibrium was achieved in both runs.…”

Thermal Evolution and Magnetic Field Generation in Terrestrial Planets and Satellites

“…5.1), it is conceivable that light elements were exsolved if the core started not too far from saturation. On the other hand, the pressure of equilibration between core and mantle materials is between 20 and 40 GPa (e.g., Thibault and Walter 1995;Li and Agee 1996), much lower than the pressure in the core. It is thus possible that during differentiation liquid iron blobs incorporated light elements at low pressures that would later not be in equilibrium at the high pressures of the core.…”

Element partitioning constraints on the light element composition of the Earth's core

“…Time-series and chemical reversal experiments demonstrated that at 5 GPa and above 2300 K, equilibrium partitioning between liquid metal and liquid silicate is accomplished in no more than five seconds [Thibault and Walter, 1995]. Moreover, in liquid phases, the characteristic length of diffusion in a 2-minute experiment is about 100 I.tm at temperatures between 1800 and 2800 K, and pressures between 15 and 25 GPa [Walker and Agee, 1989].…”