Planetary and meteoritic Mg/Si and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:msup><mml:mrow><mml:mi>δ</mml:mi></mml:mrow><mml:mrow><mml:mn>30</mml:mn></mml:mrow></mml:msup><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow></mml:math> variations inherited from solar nebula chemistry

Dauphas, N.; Poitrasson, Franck; Burkhardt, C.; Kobayashi, Hiroshi; Kurosawa, Kosuke

doi:10.1016/j.epsl.2015.07.008

Cited by 129 publications

(118 citation statements)

References 86 publications

Supporting

Mentioning

106

Contrasting

Order By: Relevance

“…In contrast, Li is the least volatile element among MVEs (e.g., Sossi and Fegley, 2018) and there is no measurable difference between CCs and OCs in Li isotopes (Pogge von Strandmann et al, 2011). Similarly, for the mass-dependent isotope systems of non-volatile elements (50 % condensation temperatures higher than Li), CCs and OCs also show no resolvable difference, such as Mg (e.g., Teng et al, 2010;Schiller et al, 2010;Bourdon et al, 2010;Pogge von Strandmann et al, 2011;Hin et al, 2017), Si (e.g., Georg et al, 2007;Fitoussi et al, 2009;Armytage et al, 2011;Dauphas et al, 2015), Ca (e.g., Simon and DePaolo, 2010;Valdes et al, 2014;Huang and Jacobsen, 2017), Ti (e.g., Greber et al, 2017;Deng et al, 2018), V (e.g., Nielsen et al, 2014;Xue et al, 2018), and Fe (e.g., Craddock and Dauphas 2011;Poitrasson et al 2004;Wang et al 2013). The fact that only isotopes of elements more volatile than Li (e.g., K, Cu, Zn and Rb) show a mass dependent dichotomy between the CCs and OCs is still intriguing.…”

Section: The K Isotope Comparison Between Carbonaceous Ordinary Andmentioning

confidence: 99%

Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system

Bloom¹,

Lodders²,

Chen³

et al. 2020

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

2020) Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system. Geochimica et Cosmochimica Acta, in press. ABSTRACT Among solar system materials there are variable degrees of depletion in moderately volatile elements (MVEs, such as Na, K, Rb, Cu, and Zn) relative to the proto-solar composition. Whether these depletions are due to nebular and/or parent-body (asteroidal or planetary) processes is still under debate. In order to help decipher the MVE abundances in early solar system materials, we conducted a systematic study of highprecision K stable isotopic compositions of a suite of whole-rock samples of wellcharacterized carbonaceous and ordinary chondrites. We analyzed 16 carbonaceous chondrites (CM1-2, CO3, CV3, CR2, CK4-5 and CH3) and 28 ordinary chondrites covering petrological types 3 to 6 and chemical groups H, L, and LL. We observed significant K isotope (δ 41 K) variations (−1.54 to 0.70 ‰) among the carbonaceous and ordinary chondrites. In general, the two major chondrite groups are distinct: The K isotope compositions of carbonaceous chondrites are largely higher than the Bulk Silicate Earth (BSE) value, whereas ordinary chondrites show K isotope compositions that are typically lower than the BSE value. Neither carbonaceous nor ordinary chondrites show clear/resolvable correlations between K isotopes and chemical groups, petrological types, shock levels, cosmic-ray exposure ages, fall/find occurrence, or terrestrial weathering. Importantly, the lack of a clear trend between K isotopes and K content among chondrites indicates that the K isotope fractionations were decoupled from the relative elemental K depletions, which is inconsistent with a single-stage partial vaporization or condensation process to account for these MVE depletion patterns among chondrites. The range of K isotope variations in the carbonaceous chondrites in this study is consistent with a fourcomponent (chondrule, refractory inclusion, matrix and water) mixing model that is able to explain the bulk elemental and isotopic compositions of the main carbonaceous chondrite groups, but requires a fractionation in K isotopic compositions in chondrules.We propose that the major control of the isotopic compositions of group averages is condensation and/or vaporization in pre-accretional (nebular) environments that is preserved in the compositional variation of chondrules. Parent-body processes, such as aqueous alteration, thermal metamorphism, and metasomatism, can mobilize K and affect the K isotopes in individual samples. In the case of the ordinary chondrites, the full range of K isotopic variations can only be explained by the combined effects of the size and relative abundances of chondrules, parent-body aqueous and thermal alteration, and possible sampling bias.compositions between different planetary materials (e.g., Earth and Moon) that were subsequently used to better understand the accretion mechanism of different planetary bodies.

show abstract

Section: The K Isotope Comparison Between Carbonaceous Ordinary Andmentioning

confidence: 99%

Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system

Bloom¹,

Lodders²,

Chen³

et al. 2020

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

show abstract

“…Melt formation by collisions is one popular scenario to consider. Dauphas et al (2015) calculated that collision-induced vaporization is only significant for targets with masses > 0.2 . However, higher impact velocities in some N-body calculations (Carter et al 2015) lead to higher estimates of vapor production by collision (Hin et al 2017).…”

Section: Planetesimal Magma Oceansmentioning

confidence: 99%

“…Because of the ambiguities resulting from competing mechanisms for iron isotope fractionation, we focus here on Mg and Si (while mindful that some ambiguity surrounds the fractionation of Si isotopes with sequestration of Si in the core as well). Pringle et al (2014) used high 29 Si/ 28 Si in angrite meteorites relative to chondrites (Figure 1) to suggest that impact-induced evaporation from colliding planetesimals controlled the Si isotopic composition of rocky bodies in the solar system, although Dauphas et al (2015) argued instead that the angrite data are best explained as the result of isotopic equilibration between SiO gas and forsterite grains in the early solar protoplanetary disk. Both Pringle et al (2014) and 3 Dauphas et al (2015) used the new angrite Si isotope ratio data to show that sequestration into Earth's core is less likely than volatility to be the primary cause of the high 29 Si/ 28 Si composition of the bulk silicate Earth (BSE) relative to chondrites.…”

Section: Introductionmentioning

confidence: 99%

Near-equilibrium isotope fractionation during planetesimal evaporation

Young

Shahar

Nimmo

et al. 2019

Icarus

View full text Add to dashboard Cite

Silicon and Mg in differentiated rocky bodies exhibit heavy isotope enrichments that have been attributed to evaporation of partially or entirely molten planetesimals. We evaluate the mechanisms of planetesimal evaporation in the early solar system and the conditions that controled attendant isotope fractionations.Energy balance at the surface of a body accreted within ~1 Myr of CAI formation and heated from within by 26 Al decay results in internal temperatures exceeding the silicate solidus, producing a transient magma ocean with a thin surface boundary layer of order < 1 meter that would be subject to foundering. Bodies that are massive enough to form magma oceans by radioisotope decay (≥ 0.1% ) can retain hot rock vapor even in the absence of ambient nebular gas. We find that a steady-state rock vapor forms within minutes to hours and results from a balance between rates of magma evaporation and atmospheric escape. Vapor pressure buildup adjacent to the surfaces of the evaporating magmas would have inevitably led to an approach to equilibrium isotope partitioning between the vapor phase and the silicate melt. Numerical simulations of this near-equilibrium evaporation process for a body with a radius of ~ 700 km yield a steady-state far-field vapor pressure of 10 -8 bar and a vapor pressure at the surface of 10 -4 bar, corresponding to 95% saturation. Approaches to equilibrium isotope fractionation between vapor and melt should have been the norm during planet formation due to the formation of steady-state rock vapor atmospheres and/or the presence of protostellar gas.We model the Si and Mg isotopic composition of bulk Earth as a consequence of accretion of planetesimals that evaporated subject to the conditions described above. The results show that the best fit to bulk Earth is for a carbonaceous chondrite-like source material with about 12% loss of Mg and 15% loss of Si resulting from near-equilibrium evaporation into the solar protostellar disk of H 2 on timescales of 10 4 to 10 5 years. .

show abstract

“…One exception observed so far is the enrichment of light Si isotopes in enstatite meteorites when compared to the Earth (Georg et al, 2007). This could be due to the presence of isotopically light Si isotopes in the metal phase of enstatite chondrites, or to fractionation between Mg-silicates and nebular gas during condensation (Georg et al, 2007;Fitoussi et al, 2009;Fitoussi and Bourdon, 2012;Savage and Moynier, 2013;Dauphas et al, 2015). The S stable isotope composition of enstatite chondrites is also different from that of the Earth; however, S is highly chalcophile and the difference can be attributed to isotope fractionation during core formation (Defouilloy et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Potassium isotopic compositions of enstatite meteorites

Zhao

Lodders

Bloom

et al. 2019

Meteorit & Planetary Scien

View full text Add to dashboard Cite

Enstatite chondrites and aubrites are meteorites that show the closest similarities to the Earth in many isotope systems that undergo mass-independent and mass-dependent isotopic fractionations. Due to the analytical challenges to obtain high-precision K isotopic compositions in the past, potential differences in K isotopic compositions between enstatite meteorites and the Earth remained uncertain. We report the first high-precision K isotopic compositions of eight enstatite chondrites and four aubrites and find that there is a significant variation of K isotopic compositions among enstatite meteorites (from −2.34‰ to −0.18‰). However, K isotopic compositions of nearly all enstatite meteorites scatter around the Bulk Silicate Earth (BSE) value. The average K isotopic composition of the eight enstatite chondrites (−0.47 ±0.57‰) is indistinguishable from the BSE value (−0.48 ±0.03‰), thus further corroborating the isotopic similarity between Earth' building blocks and enstatite meteorite precursors. We found no correlation of K isotopic compositions with the chemical groups, petrological types, shock degrees, and terrestrial weathering conditions; however, the variation of K isotopes among enstatite meteorite can be attributed to the parent-body processing. Our sample of the main-group aubrite MIL 13004 is exceptional and has an extremely light K isotopic composition (δ 41 K=−2.34 ±0.12‰). We attribute this unique K isotopic feature to the presence of abundant djerfisherite inclusions in our sample because this K-bearing sulfide mineral is predicted to be enriched in 39 K during equilibrium exchange with silicates.

show abstract

Planetary and meteoritic Mg/Si and δ30Si variations inherited from solar nebula chemistry

Cited by 129 publications

References 86 publications

Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system

Potassium isotope compositions of carbonaceous and ordinary chondrites: Implications on the origin of volatile depletion in the early solar system

Near-equilibrium isotope fractionation during planetesimal evaporation

Potassium isotopic compositions of enstatite meteorites

Contact Info

Product

Resources

About