Metal–silicate partitioning of cesium: Implications for core formation

Depletion of potassium and sodium in mantles of Mars, Moon and Vesta by core formation

“…To assess the effects of S and Si in the metal or sulfide on sulfide/metal-silicate partitioning, new interaction coefficients were derived using a thermodynamic approach (Supplementary Information). It was found that K and Na behave chalcophile, in agreement with previous studies 6 , 11 , 12 , 16 , 17 . The addition of Si to the metal has an opposite effect, resulting in a substantial decrease of their siderophile behavior, in agreement with the negative effects of Si on metal-silicate partitioning of virtually all siderophile elements 21 , 22 .…”

“…Using our derived interaction parameters, we corrected for any variability in the due to different metal compositions (Supplementary Information). Given the geochemical highly similar behavior of K and Na, we assume that the effects of S on Na are the same as that for K 11 , 17 .…”

“…It has been suggested that polymerization of silicate melts affects the sulfide-silicate and metal-silicate partitioning of K and Na 6 , 11 . Consideration of versus nbo/t, a single term proxy for the degree of silicate melt polymerization 28 , suggests the iron-loving behavior of K may be affected at the highest degrees of melt polymerization (low nbo/t, see Supplementary Information).…”

“…Previous studies were hampered by a range of analytical challenges including loss of alkalis during polishing with lubricants, relatively high detection limits of electron microprobe analysis (EMPA), “smearing” effects during sample preparation (leading to artificial enrichment of alkalis in metals by smearing alkali-rich silicate materials onto their surface) and simultaneous variation of multiple variables, prohibiting isolation of the individual parameters that affect K metal-silicate partitioning. Only two studies determined the sulfide-silicate partitioning behavior of Na 11 , 17 . As a result, it is hard to quantify to which extent these elements may have partitioned into the cores of differentiated planets, moons, and asteroids.…”

Is Mercury a volatile‐rich planet?

“…[9] A number of experimental studies investigated metal/ silicate partitioning of potassium at elevated temperatures and pressures. Studies were conducted over a range of temperatures (1650-2200 C), pressures (1-15 GPa), f O2 's (À4.6 to À1.7DIW), and bulk compositions relevant for planetary cores (i.e., <20 wt.% S in the metal) [Bouhifd et al, 2007;Chabot and Drake, 1999;Corgne et al, 2007;Mills et al, 2007]. These studies show that the S content of the metallic phase had the largest effect on the metal/silicate partition coefficient for K, which typically ranged from 0.0003 to 0.009.…”