DOI: 10.1016/j.epsl.2020.116659
论文题名: Carbon partitioning between metal and silicate melts during Earth accretion
作者: Fichtner C.E. ; Schmidt M.W. ; Liebske C. ; Bouvier A.-S. ; Baumgartner L.P.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 554 语种: 英语
中文关键词: accretion
; carbon
; core
; magma ocean
; NBO/T
; partition coefficient
英文关键词: Earth atmosphere
; Experimental mineralogy
; Mass spectrometry
; Metal melting
; Metals
; Olivine
; Oxygen
; Solubility
; Structural geology
; Carbon concentrations
; Carbon partition coefficients
; Carbon partitioning
; Experimental protocols
; Mantle concentrations
; Partition coefficient
; San Carlos olivines
; Secondary ionization
; Silicates
; accretion
; carbon
; concentration (composition)
; core (planetary)
; magma
; metal
; olivine
; partition coefficient
; silicate melt
英文摘要: In the accreting Earth and planetesimals, carbon was distributed between a core forming metallic melt, a silicate melt, and a hot, potentially dense atmosphere. Metal melt droplets segregating gravitationally from the magma ocean equilibrated near its base. To understand the distribution of carbon, its partitioning between the two melts is experimentally investigated at 1.5–6.0 GPa, 1300–2000 °C at oxygen fugacities of −0.9 to −1.9 log units below the iron-wuestite reference buffer (IW). One set of experiments was performed in San Carlos olivine capsules to investigate the effect of melt depolymerization (NBO/T), a second set in graphite capsules to expand the data set to higher pressures and temperatures. Carbon concentrations were analyzed by secondary ionization mass spectrometry (SIMS) and Raman spectra were collected to identify C-species in the silicate melt. Partition coefficients are governed by the solubility of C in the silicate melt, which varies from 0.01 to 0.6 wt%, while metal melts contain ∼7 wt% C in most samples. C solubility in the silicate melt correlates strongly with NBO/T, which, in olivine capsules, is mostly a function of temperature. Carbon partition coefficients DCmetal/silicate at 1.5 GPa, 1300–1750 °C decrease from 640(49) to 14(3) with NBO/T increasing from 1.04 to 3.11. For the NBO/T of the silicate Earth of 2.6, DCmetal/silicate is 34(9). Pressure and oxygen fugacity show no clear effect on carbon partitioning. The present results differ from those of most previous studies in that carbon concentrations in the silicate melt are comparatively higher, rendering C to be about an order of magnitude less siderophile, and the discrepancies may be attributed to differences in the experimental protocols. Applying the new data to a magma ocean scenario, and assuming present day mantle carbon mantle concentrations from 120 to 795 ppm, implies that the core may contain 0.4–2.6 wt% carbon, resulting in 0.14–0.9 wt% of this element for the bulk Earth. These values are upper limits, considering that some of the carbon in the modern silicate Earth has very likely been delivered by the late veneer. © 2020 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165467
Appears in Collections: 气候变化与战略
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作者单位: Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, Zurich, 8092, Switzerland; Institute of Mineralogy and Geochemistry, University of Lausanne, BFSH2, Lausanne, 1015, Switzerland
Recommended Citation:
Fichtner C.E.,Schmidt M.W.,Liebske C.,et al. Carbon partitioning between metal and silicate melts during Earth accretion[J]. Earth and Planetary Science Letters,2021-01-01,554