Isotopic homogeneity of iron in the early solar nebula

Abstract

The chemical and isotopic homogeneity of the early solar nebula, and the processes producing fractionation during its evolution, are central issues of cosmochemistry. Studies of the relative abundance variations of three or more isotopes of an element can in principle determine if the initial reservoir of material was a homogeneous mixture or if it contained several distinct sources of precursor material. For example, widespread anomalies observed in the oxygen isotopes of meteorites have been interpreted as resulting from the mixing of a solid phase that was enriched in 16O with a gas phase in which 16O was depleted, or as an isotopic 'memory' of Galactic evolution. In either case, these anomalies are regarded as strong evidence that the early solar nebula was not initially homogeneous. Here we present measurements of the relative abundances of three iron isotopes in meteoritic and terrestrial samples. We show that significant variations of iron isotopes exist in both terrestrial and extraterrestrial materials. But when plotted in a three-isotope diagram, all of the data for these Solar System materials fall on a single mass-fractionation line, showing that homogenization of iron isotopes occurred in the solar nebula before both planetesimal accretion and chondrule formation.

Searching for signatures of life on Mars: an Fe-isotope perspective

“…These results are consistent with other studies that have reported Fe-isotopic compositions of some of the Martian meteorites investigated in the present study (Zhu et al 2001;Poitrasson et al 2004;Weyer et al 2005). (Anand et al 2003).…”

Iron isotope fractionation in planetary crusts

“…On Earth, it is a major element in the core, the mantle and the crust (Allègre et al, 1995;Rudnick and Gao, 2003). In the past decade, the development of high-resolution Multi-Collector InductivelyCoupled-Plasma Mass-Spectrometers (MC-ICP-MS) has allowed measurements of iron isotope composition at high precision (Belshaw et al, 2000;Zhu et al, 2001;Weyer and Schwieters, 2003;Dauphas et al, 2009b;Millet et al, 2012). Following this improvement, small yet resolvable iron isotopic variations in igneous rocks have been discovered (Poitrasson et al, 2004;Weyer et al, 2005;Schoenberg and von Blanckenburg, 2006;Weyer and Ionov, 2007;Heimann et al, 2008;Teng et al, 2008Teng et al, , 2011Dauphas et al, 2009a;Weyer and Seitz, 2012).…”

Fe Isotopic Compositions of Modern Seafloor Hydrothermal Systems and Their Influence Factors

“…The range of 56 Fe values in meteorites is from −0.15‰ to 0.18‰, with an average 56 Fe of 0.03 ± 0.06‰ ( = 71) ( Figure 1). The Fe isotope composition of Earth materials is generally thought to be similar to the average of meteorites [1].…”

“…The Fe isotope composition of the mantle is controlled primarily by the Fe isotope compositions of mantle peridotites. This range is from −1.1‰ to 0.48‰, with an average 56 Fe of −0.05 ± 0.21‰ ( = 364). The Fe isotope composition of the oceanic crust is controlled by the Fe isotope compositions of basalts.…”

“…Fe is involved in the physiochemical aspects of biological and inorganic processes in high-and low-temperature geologic environments. Fe has four stable isotopes in nature, 54 Fe, 56 Fe, 57 Fe, and 58 Fe, whose abundances are 5.84%, 91.76%, 2.12%, and 0.28%, respectively. Recently, the rapid development of a highly accurate multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) technique for measuring Fe isotopes has the enabled broad application of Fe isotopes in the Earth science [1,2].…”