Nitrogen and carbon fractionation during core–mantle differentiation at shallow depth

摘要: Abstract One of the most remarkable observations regarding volatile elements in solar system is depletion N bulk silicate Earth (BSE) relative to chondrites, leading a particularly high and non-chondritic C:N ratio. The may reflect large-scale differentiation events such as sequestration Earth's core or massive blow off early atmosphere, alternatively characteristics late-added volatile-rich veneer. As behavior during planetary processes poorly constrained, we determined together partitioning C between Fe–N–C metal alloy two different melts (a terrestrial martian basalt). Conditions spanned range fO2 from ΔIW−0.4 ΔIW−3.5 at 1.2 3 GPa, 1400 °C 1600 °C, where ΔIW logarithmic difference experimental that imposed by coexistence crystalline Fe wustite. ( D / ) depends chiefly on fO2, decreasing 24 ± 0.3 0.1 with fO2. also decreases increasing temperature pressure similar though effect subordinate. In contrast, partition coefficients show no evidence dependence but diminish temperature. At 1400 °C, increase linearly 300 30 670 50 . however, they ΔIW−0.7 ΔIW−2 87 240 decrease ΔIW−3.3 99 6 Enhanced temperatures under reduced conditions stabilization C–H species (most likely CH4). No significant compositional for either evident, perhaps owing comparatively basalts investigated. modestly (ΔIW−0.4 −2.2), more compatible core-forming than molten 1 ≤ ), while (ΔIW−2.2 ΔIW−3.5), becomes magma ocean phase. highly siderophile all investigated 100 700 ). Therefore, volatiles affects N, lowers ratio BSE. Consequently, BSE cannot be explained formation. Mass balance modeling suggests formation combined atmosphere blow-off produce non-metallic BSE, accretion C-rich late veneer can account observed