Carbon and nitrogen in carbonaceous chondrites: Elemental abundances and stable isotopic compositions

Pearson, V. K.; Sephton, M. A.; Franchi, I. A.; Gibson, J. M.; Gilmour, I.

doi:10.1111/j.1945-5100.2006.tb00459.x

Cited by 171 publications

(160 citation statements)

References 50 publications

Supporting

Mentioning

143

Contrasting

Order By: Relevance

“…The range of δ 13 C values for the bulk Earth is in fact more consistent with those observed for chondrites and other meteorites (−24‰ to +5‰) (2,49,50). Recently, a conceptually similar, but qualitative model has been presented (48).…”

supporting

confidence: 78%

Carbon-bearing iron phases and the carbon isotope composition of the deep Earth

Juske

Polyakov

2014

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The carbon budget and dynamics of the Earth’s interior, including the core, are currently very poorly understood. Diamond-bearing, mantle-derived rocks show a very well defined peak at δ13C ≈ −5 ± 3‰ with a very broad distribution to lower values (∼−40‰). The processes that have produced the wide δ13C distributions to the observed low δ13C values in the deep Earth have been extensively debated, but few viable models have been proposed. Here, we present a model for understanding carbon isotope distributions within the deep Earth, involving Fe−C phases (Fe carbides and C dissolved in Fe−Ni metal). Our theoretical calculations show that Fe and Si carbides can be significantly depleted in 13C relative to other C-bearing materials even at mantle temperatures. Thus, the redox freezing and melting cycles of lithosphere via subduction upwelling in the deep Earth that involve the Fe−C phases can readily produce diamond with the observed low δ13C values. The sharp contrast in the δ13C distributions of peridotitic and eclogitic diamonds may reflect differences in their carbon cycles, controlled by the evolution of geodynamical processes around 2.5–3 Ga. Our model also predicts that the core contains C with low δ13C values and that an average δ13C value of the bulk Earth could be much lower than ∼−5‰, consistent with those of chondrites and other planetary body. The heterogeneous and depleted δ13C values of the deep Earth have implications, not only for its accretion−differentiation history but also for carbon isotope biosignatures for early life on the Earth.

show abstract

supporting

confidence: 78%

Carbon-bearing iron phases and the carbon isotope composition of the deep Earth

Juske

Polyakov

2014

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…The δ 13 C and C/N values as well as the earlier determined Ir concentrations (4) obtained from the Lommel black material fall completely within the range of terrestrial organic matter (29)(30)(31). However, extraterrestrial organic carbon displays a broad range of isotopic compositions that also include those of terrestrial organic matter (32)(33)(34)(35). For example, bulk samples of nanodiamonds separates extracted from primitive chondrites yield δ 13 C values around −38.8 to −32.5‰ (i.e., close to the range obtained here), but somewhat higher C/N ratios from 75 to 555 (32).…”

Section: Discussionmentioning

confidence: 67%

Nanodiamonds do not provide unique evidence for a Younger Dryas impact

Tian

Schryvers

Claeys

2010

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Microstructural, δ13C isotope and C/N ratio investigations were conducted on excavated material from the black Younger Dryas boundary in Lommel, Belgium, aiming for a characterisation of the carbon content and structures. Cubic diamond nanoparticles are found in large numbers. The larger ones with diameters around or above 10 nm often exhibit single or multiple twins. The smaller ones around 5 nm in diameter are mostly defect-free. Also larger flake-like particles, around 100 nm in lateral dimension, with a cubic diamond structure are observed as well as large carbon onion structures. The combination of these characteristics does not yield unique evidence for an exogenic impact related to the investigated layer.

show abstract

“…No analyses are yet available for recently identified CK3 chondrites, however, the extensively weathered nature of these terrestrial finds (Huber et al, 2006) would severely limit the usefulness of such data when attempting comparisons with CV falls. This fact is clearly illustrated by the heavily altered CK4 find Maralinga which has carbon abundance of 0.28 wt% (Pearson et al, 2006). Antarctic CKs appear to have suffered less terrestrial contamination.…”

Section: Carbon Contentmentioning

confidence: 86%

“…The CK4 fall Karoonda has a carbon abundance of 0.07 wt%, compared to 0.27 to 1.5 wt% in CVs (Pearson et al, 2006). No analyses are yet available for recently identified CK3 chondrites, however, the extensively weathered nature of these terrestrial finds (Huber et al, 2006) would severely limit the usefulness of such data when attempting comparisons with CV falls.…”

Section: Carbon Contentmentioning

confidence: 99%

The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

100

195

View full text Add to dashboard Cite

CK chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of Fe,Ni-metal. Although the group is predominately composed of equilibrated meteorites (types 4 to 6), in recent years a significant number of new samples have been classified as being either CK3 or CK3-anomalous. These unequilibrated CKs often display a close affinity with members of the CV oxidized subgroup. CKs and CVs (oxidized subgroup) may therefore form a continuum and by implication could be derived from a single common parent body. To investigate the relationship between these two groups a detailed study of the oxygen isotope composition, opaque mineralogy and major and trace element geochemistry of a suite of CV and CK chondrites has been undertaken. The results of oxygen isotope analysis confirm the close affinity between CV and CK chondrites, while excluding the possibility of a linkage between the CO and CK groups. Magnetites in both CV and CK chondrites show significant compositional similarities, but high Ti contents are a diagnostic feature of the latter group. The results of major and trace element analysis demonstrate that both CV and CK chondrites show overlapping variation. Supporting evidence for a single common source for both groups comes from their similar cosmic-ray exposure age distributions. Recent reflectance spectral analysis is consistent with both the CVs and CKs being derived from Eos family asteroids, which are believed to have formed by the catastrophic disruption of a single large asteroid. Thus, a range of evidence appears to be consistent with CV and CK chondrites representing samples from a single thermally stratified parent body. In view of the close similarity between CV and CK chondrites some modification of the present classification scheme may be warranted, possibly involving integration of the two groups. One means of achieving this would be to reassigned CK chondrites to a subgroup of the oxidized CVs. It is recognized that a full evaluation of this proposal may require further study of the still poorly understood CK3 chondrites. ACCEPTED MANUSCRIPT3

show abstract

Carbon and nitrogen in carbonaceous chondrites: Elemental abundances and stable isotopic compositions

Cited by 171 publications

References 50 publications

Carbon-bearing iron phases and the carbon isotope composition of the deep Earth

Carbon-bearing iron phases and the carbon isotope composition of the deep Earth

Nanodiamonds do not provide unique evidence for a Younger Dryas impact

The relationship between CK and CV chondrites

Contact Info

Product

Resources

About