Development of an isolation procedure and MC-ICP-MS measurement protocol for the study of stable isotope ratio variations of nickel

Abstract

Variations in the isotopic composition of Ni resulting from natural mass-dependent processes in terrestrial or extraterrestrial conditions, inhomogeneous distribution of nucleosynthetic components and/or ingrowth from radioactive parent nuclides, help us to further understand the early formation history of Solar System materials and the nature of the processes these materials subsequently experienced. In studies of Ni isotope systematics, mass-dependent variations in the isotopic composition of Ni are often bypassed because of the challenges associated with the sample preparation. At the level of natural variation studied, Ni isotope ratio measurements are extremely sensitive to spectral interference, artificial on-column isotope fractionation and possibly even to the mass bias correction model applied. To adequately address these complications, an isolation procedure and measurement protocol relying on multi-collector ICP-mass spectrometry (MC-ICP-MS) have been designed and validated in this work. The overall reproducibility obtained based on repeated measurement of a Sigma-Aldrich high-purity Ni standard is 0.036&, 0.049 parts per thousand, 0.078 parts per thousand and 0.53 parts per thousand for delta Ni-60/58, delta Ni-61/58, delta Ni-62/58 and delta Ni-64/58, respectively (n = 14; 2 SD). Nickel isotope ratio variations have been studied in a set of iron meteorites and geological reference materials, and the results obtained, except for those suffering from an elevated Zn-64 background, show good agreement with the available literature data. By using the flexible generalized power law with a variable discrimination exponent and the three-isotope method, the processes underlying natural mass fractionation of Ni for terrestrial reference materials were found to have a mixed equilibrium/kinetic nature. Mass-dependent Ni fractionation was observed between sample fractions of the Canyon Diablo iron meteorite, and the extracted fractionation factor beta corresponds to isotope partitioning following the power law

Optimisation of Lithium Chromatography for Isotopic Analysis in Geological Reference Materials by MC‐ICP‐MS

“…(e) The presence of organics in the final elution disturbs isotopic measurements in a non‐spectral way (Chernonozhkin et al . ). (f) Organic matter could induce complexation with target cations, making subsequent ion‐exchange separation steps ineffective.…”

“…Mineral acid and methanol mixtures containing a high level of impurities may exacerbate instrumental baseline shifts (Gao and Casey 2012). (e) The presence of organics in the final elution disturbs isotopic measurements in a non-spectral way (Chernonozhkin et al 2015). (f) Organic matter could induce complexation with target cations, making subsequent ion-exchange separation steps ineffective.…”

Nickel isotopic composition of the mantle

“…1 (smaller triangles). Previously published data for unaltered peridotite samples are all analyses of the rock reference material PCC-1, DTS-1, DTS-2 (USGS) and JP-1 (GJS) (Steele et al, 2011;Gueguen et al, 2013;Chernonozhkin et al, 2015). The USGS reference sample PCC-1 is a harzburgite (Cazadero ultramac massif, California) and DTS-1, -2 (Twin Sisters Mountain, Washington) and JP-1 (Horoman dunite, Japan; Imai et al, 1995) are dunites.…”

“…Nickel stable isotopes are a relatively new geochemical tracer that has not been evaluated in detail in terrestrial high-temperature environments. A number of studies have attempted to quantify the degree of δ 60 Ni (permil deviation in 60 Ni/ 58 Ni relative to the NIST SRM 986 Ni isotope standard) variation in igneous rocks, including mantle derived materials (Cameron et al, 2009;Steele et al, 2011;Gall et al, 2012Gall et al, , 2013Gueguen et al, 2013;Chernonozhkin et al, 2015;Ratié et al, 2015;Estrade et al, 2015). However, most of these data are limited to rock standards or reference materials, and no systematic Ni stable isotope study of mantle rocks has been published.…”

PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS

“…In particular, we have used high-precision isotopic analyses by multi-collector ICP-MS (Inductively Coupled Plasma Mass Spectrometry/Spectrometer). A novel method was developed for the isolation of Ni for its subsequent isotopic analysis via multi-collector ICP-MS (Chernonozhkin et al 2015). Laterally resolved isotopic analysis (microdrill sampling) of Fe and Ni was shown to provide complementary information.…”