Cosmogenic effects on Cu isotopes in IVB iron meteorites

Chen, Heng; Moynier, Frédéric; Humayun, M.; Bishop, Matthew Cole; Williams, Jeffrey T.

doi:10.1016/j.gca.2016.03.006

Cited by 13 publications

(8 citation statements)

References 66 publications

(134 reference statements)

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“…The Cu concentrations of the samples were checked and adjusted to match the Cu standard solution within 10%. The geological reference materials BHVO-2, BCR-2, BIR-1a, AGV-2, and GSP-2 were digested and measured along with samples, and the results agree well with previously published values within ±0.05‰ (2 SD; Table S2; Chen et al, 2016;Hou et al, 2016;Huang et al, 2017;Li et al, 2009;Moeller et al, 2012;Wang et al, 2019;Weinstein et al, 2011). To verify the Cu isotope data, the digestion solutions of eight samples were independently measured at the Metal Stable Isotope Laboratory of the University of Science and Technology of China (USTC) for comparison.…”

Section: Bulk-rock Copper Isotopessupporting

confidence: 87%

Copper Isotope Variations During Magmatic Migration in the Mantle: Insights From Mantle Pyroxenites in Balmuccia Peridotite Massif

Zou

Wang

et al. 2019

JGR Solid Earth

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The crust shows large variations in Cu isotopic composition (δ 65 Cu relative to NIST 976) resulting from redox reactions and other supergene processes. The significant range of δ 65 Cu in mantle peridotites thus could be ascribed to recycled crustal materials and/or oxidative mantle metasomatism. However, the influence of normal magmatic fractionation processes on δ 65 Cu variations remains poorly understood, and it is unclear whether the magmatic processes also lead to large δ 65 Cu variations in mantle rocks. To address the issue, we present bulk-rock δ 65 Cu of fresh mantle pyroxenites from the Balmuccia peridotite massif, Northern Italy. These pyroxenites formed by melt-peridotite reaction and mineral accumulation from MORB-to OIB-like, sulfide-saturated basic magmas. Mass balance calculations show that sulfide phases host >98 wt % of the Cu budget of bulk rocks (87−484 μg/g). The pyroxenites show significant variations of δ 65 Cu from −0.66‰ to 0.66‰, which cover the range known for peridotites, including metasomatized ones. Three subsamples from the same pyroxenite layer display >0.3‰ decrease in δ 65 Cu with progressive differentiation. Nevertheless, δ 65 Cu does not display correlations with indicators of magmatic differentiation (e.g., Mg# and Cu/Pd) for all pyroxenites in this study. This might be attributed to variable extents of magmatic sulfide segregation for different samples and/or varying δ 65 Cu of the pyroxenite parent magmas, which were also affected by reactive migration through peridotites. The combined processes can change δ 65 Cu of evolving magmas and reacted peridotites and lead to Cu isotopic heterogeneity in the mantle, without involvement of oxidative metasomatism or recycled crustal materials.

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Section: Bulk-rock Copper Isotopessupporting

confidence: 87%

Copper Isotope Variations During Magmatic Migration in the Mantle: Insights From Mantle Pyroxenites in Balmuccia Peridotite Massif

Zou

Wang

et al. 2019

JGR Solid Earth

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“…The magnitude of the change in the 62 Ni abundance agrees with the estimate by Chen et al. (2016). Spallation reactions lead to only very small changes in the five Ni isotopes; the largest effect is on 61 Ni (≈0.3 ppm), whereas the effects on the remaining isotopes are all <0.01 ppm.…”

Section: Discussionsupporting

confidence: 90%

“…2019), and Cu (Chen et al. 2016) . Effects from GCRs have also been shown to affect chronometers in iron meteorites, including 107 Pd‐ 107 Ag (Matthes et al.…”

Section: Introductionmentioning

confidence: 99%

Galactic cosmic ray effects on iron and nickel isotopes in iron meteorites

Cook

Leya

Schönbächler

2020

Meteorit & Planetary Scien

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We present model calculations for cosmogenic production rates in order to quantify the potential effects of spallation and neutron capture reactions on Fe and Ni isotopes in iron meteorites. We aim to determine whether the magnitude of any cosmogenic effects on the isotopic ratios of Fe and/or Ni may hinder the search for nucleosynthetic variations in these elements or in the application of the 60Fe‐60Ni chronometer. The model shows that neutron capture reactions are the dominant source of shifts in Fe and Ni isotopic ratios and that spallation reactions are mostly negligible. The effects on 60Ni are sensitive to the Co/Ni ratio in the metal. The total galactic cosmic ray (GCR) effects on 60Ni and 64Ni can be minimized through the choice of normalizing isotopes (61Ni/58Ni versus 62Ni/58Ni). In nearly all cases, the GCR effects (neutron capture and/or spallation) on Fe and Ni isotopic ratios are smaller than the current analytical resolution of the isotopic measurements. The model predictions are compared to the Fe and Ni isotopic compositions measured in a suite of six group IAB irons with a range of cosmic ray exposure histories. The experimental data are in good agreement with the model results. The minimal effects of GCRs on Fe and Ni isotopes should not hamper the search for nucleosynthetic variations in these two elements or the application of the 60Fe‐60Ni chronometer in iron meteorites or chondrites.

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“…Mass-dependent isotopic fractionations due to evaporation from a melt will preferentially remove lighter isotopes in the vapor phase and leave heavier isotopes in the residue (Humayun and Clayton 1995), a kinetic isotope effect that might be found in volatile elements like Cu and Zn (Moynier et al 2006). However, d 65 Cu in IVB irons is in agreement with other irons and carbonaceous chondrites after correction of cosmogenic effects (Luck et al 2005;Chen et al 2016). Recent Mo isotope measurements (Burkhardt et al 2014) show that there is no mass-dependent fractionation in Mo isotopes between IVB irons and other irons (IVA, IIIAB, and IIAB), enstatite chondrites, ordinary chondrites, and some carbonaceous chondrites.…”

Section: Mass-dependent Fractionationmentioning

confidence: 59%

“…Cosmogenic effects are caused by meteorite exposure to galactic cosmic rays (GCR) that produce secondary neutrons that are captured by nuclei with suitable cross sections to generate new nuclides, changing the isotope ratio of the elements affected. This process has been reported for a variety of isotopes in iron meteorites, including 182 W (Leya et al 2003;Markowski et al 2006;Qin et al 2008); 189 Os and 190 Os (Walker 2012;Wittig et al 2013);192 Pt, 194 Pt, and 196 Pt (Kruijer et al 2013(Kruijer et al , 2014a(Kruijer et al , 2014bLeya and Masarik 2013;Wittig et al 2013); 104 Pd ; 100 Ru (Fischer-G€ odde et al 2015); and 63 Cu (Chen et al 2016). The largest effects are observed in some of the IVB irons.…”

Section: Introductionmentioning

confidence: 61%

Natural variations in the rhenium isotopic composition of meteorites

Liu

Humayun

2016

Meteorit & Planetary Scien

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Rhenium is an important element with which to test hypotheses of isotope variation. Historically, it has been difficult to precisely correct the instrumental mass bias in thermal ionization mass spectrometry. We used W as an internal standard to correct mass bias on the MC‐ICP‐MS, and obtained the first precise δ187Re values (~±0.02‰, 2SE) for iron meteorites and chondritic metal. Relative to metal from H chondrites, IVB irons are systematically higher in δ187Re by ~0.14 ‰. δ187Re for other irons are similar to H chondritic metal, although some individual samples show significant isotope fractionation. Since 185Re has a high neutron capture cross section, the effect of galactic cosmic‐ray (GCR) irradiation on δ187Re was examined using correlations with Pt isotopes. The pre‐GCR irradiation δ187Re for IVB irons is lower, but the difference in δ187Re between IVB irons and other meteoritic metal remains. Nuclear volume‐dependent fractionation for Re is about the right magnitude near the melting point of iron, but because of the refractory and compatible character of Re, a compelling explanation in terms of mass‐dependent fractionation is elusive. The magnitude of a nucleosynthetic s‐process deficit for Re estimated from Mo and Ru isotopes is essentially unresolvable. Since thermal processing reduced nucleosynthetic effects in Pd, it is conceivable that Re isotopic variations larger than those in Mo and Ru may be present in IVBs since Re is more refractory than Mo and Ru. Thus, the Re isotopic difference between IVBs and other irons or chondritic metal remains unexplained.

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Cosmogenic effects on Cu isotopes in IVB iron meteorites

Cited by 13 publications

References 66 publications

Copper Isotope Variations During Magmatic Migration in the Mantle: Insights From Mantle Pyroxenites in Balmuccia Peridotite Massif

Copper Isotope Variations During Magmatic Migration in the Mantle: Insights From Mantle Pyroxenites in Balmuccia Peridotite Massif

Galactic cosmic ray effects on iron and nickel isotopes in iron meteorites

Natural variations in the rhenium isotopic composition of meteorites

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