Modeling fractional crystallization of group IVB iron meteorites

Walker, Richard J.; McDonough, William F.; Honesto, J.; Chabot, N. L.; McCoy, T. J.; Ash, R. D.; Bellucci, Jeremy J.

doi:10.1016/j.gca.2008.01.021

Cited by 140 publications

(224 citation statements)

References 39 publications

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“…That study recognized considerable variance of data about the isochron they reported and eliminated data for three samples that would have been consistent with an older age. The new isochron age is similar to the Re-Os ages of other iron meteorite groups (Luck et al, 1980;Horan et al, 1992Horan et al, , 1998Shen et al, 1996;Smoliar et al, 1996;Cook et al, 2004;Walker et al, 2008). For our suite of bulk samples, Os concentrations vary by as much as three orders of magnitude over the entire range of IVA irons, while Ru, Pt and Pd vary by less than factors of five.…”

Section: Re-187 Os and Highly Siderophile Elementssupporting

confidence: 83%

“…3). The pattern shapes for evolved (high Ni) IVA irons are distinct compared to typical patterns for other magmatic iron groups (Pernicka and Wasson, 1987;Wasson, 1999;Petaev and Jacobsen, 2004;Walker et al, 2008), yet the overall trend towards greatly diminished Re, Os and Ru concentrations with increasing level of fractionation (e.g., Ni) is also present in the group IIAB and IIIAB iron meteorite suites (e.g., Cook et al, 2005). Abundances of Pd (and Au) increase with increasing level of fractionation, indicating that they were the only incompatible elements among the group of HSE measured.…”

Section: Re-187 Os and Highly Siderophile Elementsmentioning

confidence: 93%

“…The chemical-separation and mass spectrometric techniques used in this study for Re-Os isotopic analysis and isotope dilution analysis of Ir, Ru, Pt and Pd have been previously published (Shirey and Walker, 1995;Rehkämper et al, 1997;Cook et al, 2004;Becker et al, 2006;Walker et al, 2008). A brief description follows with additional details provided in the Electronic Annex.…”

Section: O and Dmentioning

confidence: 99%

“…Prior studies have shown that the variance about the mean for multiple chunks of iron taken from the same piece for HSE is 62% (Walker et al, 2008). This level of reproducibility includes minor variations resulting from analytical methods (weighing spikes and samples, mass spectrometric uncertainties including error magnification resulting from non-ideal spiking), as well as sample heterogeneity.…”

Section: O and Dmentioning

confidence: 99%

“…The mass spectrometer was operated in a dynamic peak hopping mode with mass/charge positioning achieved by a combination of magnet current shifts and voltage offsets (Hamester et al, 1999). Details regarding the analytical system and mode of operation for iron meteorites have been recently published (Walker et al, 2008) and are only briefly reviewed here. Additional details are provided in the Electronic Annex.…”

Section: Laser Ablation Icp-msmentioning

confidence: 99%

See 4 more Smart Citations

Group IVA irons: New constraints on the crystallization and cooling history of an asteroidal core with a complex history

McCoy

Walker

Goldstein

et al. 2011

Geochimica et Cosmochimica Acta

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Section: Re-187 Os and Highly Siderophile Elementssupporting

confidence: 83%

Section: Re-187 Os and Highly Siderophile Elementsmentioning

confidence: 93%

Section: O and Dmentioning

confidence: 99%

Section: O and Dmentioning

confidence: 99%

Section: Laser Ablation Icp-msmentioning

confidence: 99%

See 3 more Smart Citations

Group IVA irons: New constraints on the crystallization and cooling history of an asteroidal core with a complex history

McCoy

Walker

Goldstein

et al. 2011

Geochimica et Cosmochimica Acta

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Multistage Core Formation in Planetesimals Revealed by Numerical Modeling and Hf‐W Chronometry of Iron Meteorites

et al. 2018

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Iron meteorites provide some of the most direct insights into the processes and timescales of core formation in planetesimals. Of these, group IVB irons stand out by having one of the youngest 182Hf‐182W model ages for metal segregation (2.9 ± 0.6 Ma after solar system formation), as well as the lowest bulk sulfur content and hence highest liquidus temperature. Here, using a new model for the internal evolution of the IVB parent body, we show that a single stage of metal‐silicate separation cannot account for the complete melting of pure Fe metal at the relatively late time given by the Hf‐W model age. Instead, a complex metal‐silicate separation scenario is required that includes migration of partial silicate melts, formation of a shallow magma ocean, and core formation in two distinct stages of metal segregation. In the first stage, a protocore formed at ≈1.5 Ma via settling of metal particles in a mantle magma ocean, followed by metal segregation from a shallow magma ocean at ≈5.4 Ma. As these stages of metal segregation occurred at different times, the two metal fractions had different 182W compositions. Consequently, the final 182W composition of the IVB core does not correspond to a single differentiation event, but represents the average composition of early‐ and late‐segregated core fractions. Our best fit model indicates an ≈100 km radius for the IVB parent body and provides an accretion age of ≈0.1–0.5 Ma after solar system formation. The computed solidification time is, furthermore, consistent with the Re‐Os age for crystallization of the IVB core.

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Additive manufacturing of platinum group element (PGE) reference materials with a silica matrix

Sio

Parsons‐Davis

Lee

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale The microanalytical community has an outstanding need for platinum group element (PGE) reference materials, particularly for trace element analysis by laser ablation inductively coupled plasma mass spectrometry (LA‐ICPMS). National Institute of Standards and Technology (NIST) glasses contain Rh, Pd, and Pt, but lack Ru, Os, and Ir. Synthesis of silicate PGE standards has proven difficult due the tendency of PGEs to form metallic nuggets. Methods Additive manufacturing methods were used to produce PGE standards with a silica matrix. Monodispersed submicron PGE‐doped Stöber particles were used as feedstock materials for electrophoretic deposition (EPD). Two‐cm‐sized samples produced by EPD were subsequently densified by thermal processing. The homogeneity of PGEs was tested using LA‐ICPMS and concentrations were measured by laser ablation and solution ICPMS. Results The PGE concentrations ranged from 0.5 to 3 μg/g. The inhomogeneity was at the 3% RSD level for Ru, Rh, Ir, and Os throughout and 5% for Pt and Pd in the interior of the samples. Based on LA‐ICPMS analyses, the interiors of the two samples have near identical concentrations in PGEs. Conclusions The samples fabricated in this study represent the most complete and homogeneous PGE standards produced with a silicate matrix. The ability to produce multiple samples with the same composition provides opportunities for validating methods, monitoring long‐term reproducibility, and facilitating interlaboratory comparisons.

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Modeling fractional crystallization of group IVB iron meteorites

Cited by 140 publications

References 39 publications

Group IVA irons: New constraints on the crystallization and cooling history of an asteroidal core with a complex history

Group IVA irons: New constraints on the crystallization and cooling history of an asteroidal core with a complex history

Multistage Core Formation in Planetesimals Revealed by Numerical Modeling and Hf‐W Chronometry of Iron Meteorites

Additive manufacturing of platinum group element (PGE) reference materials with a silica matrix

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