Iron Isotopic Measurement Using Large-Geometry High-Resolution Multi-Collector Inductively Coupled Plasma Mass Spectrometer

Abstract

High-precision and accurate Fe isotopic analyses are essential for various geological processes. In this study, Fe isotopic measurements were optimized on a large-geometry, high-resolution Nu Plasma 1700 MC-ICP-MS instrument, which can distinguish Ar-related interferences completely as opposed to other general-sized MC-ICP-MS instruments. Under the conditions of high mass resolution, complete separation of Ar-related interference can be achieved. We evaluated the type and intensity of all Ar-related interferences. The effects of the acid molarity, concentration mismatch, residual HCl, and matrix elements were also evaluated. The results demonstrate that the molarity of the acid, residual HCl, and Cr significantly affected the precision of the Fe isotopic measurements. Fe was purified by one-step column anion-exchange separation using the anion resin AG-MP-1M. The long-term external precisions of δ 56 Fe and δ 57 Fe were greater than ± 0.03‰ (2SD) and ± 0.06‰ (2SD), respectively. The Fe isotopic compositions of the five geological reference materials measured in this study agreed with previously published data, within uncertainties.

New Potential Sulfide Reference Materials for Microbeam S‐Fe‐Cu Isotope Measurements

“…According to the research results of Lei et al . (2022), when Cr/Fe in the sample is less than 1.00 × 10 ‐4 , no detectable deviation in Fe isotope ratio will be observed. Despite the heterogeneous distribution of certain trace elements, they do not affect the determination of the S‐Fe‐Cu isotopes.…”

“…Geological reference materials BCR-2, BHVO-2 and GSB, were analysed as quality control reference materials. Details of the solution Fe isotopic measurements have been described by Lei et al (2022).…”

“…In general, S isotopes are measured by gas-source isotope ratio mass spectrometry (GS-IRMS) (Ke et al 2017), whereas Fe and Cu isotope ratios are usually determined by solution nebulisation multi-collector ICP-MS (SN-MC-ICP-MS) after complex whole-rock dissolution and chemical purification processes (Sossi et al 2015, Zhu et al 2019). These bulk analytical techniques are considered the standard methods for isotope ratio determinations; however, chemical pretreatment is time-consuming and requires large amounts of reagents (Baublys et al 2004, Zhu et al 2019, Lei et al 2022. In particular, avoiding contamination from inclusions or to distinguishing the information from the small mineral scale is difficult.…”

Tracing Sediment Melt Activity in the Sub‐Continental Lithosphere: Insights From Zn‐Fe Stable Isotopes

“…Zinc and Fe isotopic analyses were conducted at the State Key Laboratory of Geological Processes and Mineral Resources at China University of Geoscience (Wuhan), utilizing established protocols by Lei et al. (2022) and Zhu et al. (2019).…”

“…Zinc and Fe isotopic analyses were conducted at the State Key Laboratory of Geological Processes and Mineral Resources at China University of Geoscience (Wuhan), utilizing established protocols by Lei et al (2022) and Zhu et al (2019). Clinopyroxene, phlogopite, and spinel grains from the clinopyroxenites were handpicked under a binocular microscope.…”