Isotope fractionation and concentration measurements of Zn in meteorites determined by the double spike, IDMS‐TIMS techniques

Abstract

Abstract-The isotope fractionation of Zn in meteorites has been measured for the first time using thermal ionization mass spectrometry and a double spiking technique. The magnitude of dZn ranged from )0.29 to +0.38& amu )1 for five stone meteorites whereas the iron meteorite Canyon Diablo displays dZn of 1.11 ± 0.11& amu )1 . The results for chondrites in this work can be divided into positive and negative dZn, supporting a previous proposal that chondrites are a mixture of materials from two different temperature sources. The Zn isotope fractionation present in meteorites may represent a primordial heterogeneity formed in the early solar system. An anomalous isotopic composition of Zn obtained for the Redfields iron meteorite suggests large-scale inherited isotope heterogeneity of the protosolar nebula, or the presence of a parent body that has formed within its own isotopically anomalous reservoir. These anomalies are in the same direction but smaller than nuclear field shift effects observed in chemical exchange reactions. The isotope dilution mass spectrometry (IDMS) technique was used to measure Zn concentration, yielding a range from 20

Zinc isotopic composition of iron meteorites: Absence of isotopic anomalies and origin of the volatile element depletion

“…As expected, all samples fall on a mass‐dependent fractionation line with a slope of 1.981 ( R 2 = 0.999) on the three‐isotope plot. In contradiction to Ghidan and Loss (), this study shows that Redfields' Zn isotopic composition is mass‐dependent just like any other bulk meteorite analyzed so far. The ranges of δ 66 Zn values significantly overlap for the different meteorite groups, with the isotopically heaviest sample being the IIE Watson (δ 66 Zn = 5.61‰) and the lightest being the III AB Casas Grandes (δ 66 Zn = −0.59‰ as measured by Luck et al.…”

“…Therefore, Zn isotopic fractionation in Redfields is totally mass‐dependent. Moreover, the Zn concentration of Redfields measured in this study (6.8 ppm) is very close to the isotope dilution measurement of Ghidan and Loss () (7.2 ppm) ensuring that our Zn purification technique is working correctly. The difference in isotopic compositions might be due to the heterogeneity of the samples or problem with measurement and data analysis.…”

“…Ghidan and Loss () reported the Redfields iron meteorite to have an anomalous Zn isotopic composition, stating its deviation from the Zn standard IRMM 3702 to be 5.6 ± 0.4 for δ 66 Zn, 4.4 ± 3.6 for δ 67 Zn, and 21.0 ± 0.9 for δ 68 Zn in unspiked samples. When normalized to 68 Zn/ 64 Zn, the isotope 66 Zn anomaly would be approximately −52ε units, which is significantly larger than the largest anomaly found in CAIs (+16.7ε in Allende FUN inclusion; Völkening and Papanastassiou ).…”

Zinc isotopes in HEDs: Clues to the formation of 4-Vesta, and the unique composition of Pecora Escarpment 82502

“…The average Zn fractionation for this group of HED meteorites was approximately zero, similar to ordinary chondrites (Luck et al, 2005;Moynier et al, 2007;Ghidan and Loss, 2011). Considering only the eucrite falls, the average d 66 Zn value of +0.50 ± 0.51& was identical to the CI chondrites reported by Luck et al (2005), who found mean d 66 Zn = +0.49& and +0.47& for Orgueil and Ivuna, respectively.…”

“…Zinc isotopic heterogeneity has been previously reported in chondrites and in iron meteorites by Luck et al (2005) and by Ghidan and Loss (2011). Ghosh and McSween (1998) proposed a model for Vesta of a melted center with an unmelted outer shell which would be expected to retain some isotopic heterogeneity.…”