Geostandards and Geoanalytical Research最新文献

Although sulfur is a relatively abundant element, measurement results with small uncertainties remain challenging to achieve, especially at S mass fractions below 100 μg g^-1. We report > 1700 measurement results of S for thirty-seven geological reference materials including igneous, metamorphic and sedimentary rocks, and one soil. Measurement results were obtained in two laboratories (Macquarie GeoAnalytical and Géosciences Montpellier) over a long period of time ≈ 25 years (1997–2022), using several measurement procedures: X-ray fluorescence, high temperature iodo titration and elemental analysers equipped with thermal conductivity and/or infra-red detectors. Sulfur mass fractions for these diverse geological reference materials range between 5.5 and 11,395 μg g^-1. While the comprehensive data set reported here should contribute significantly to a better characterisation of the S mass fractions of widely used geological reference materials, computed uncertainties, data distribution and comparison to published values still indicate heterogeneous distribution of S carrier(s) and analytical bias.

This study presents high-precision W isotopic measurement results using the ¹⁸⁰W-¹⁸³W double spike technique with MC-ICP-MS. The effects of isobaric and polyatomic interferences on W isotopic measurements were evaluated. The δ^186/184W values were not significantly affected when the solution had Hf/W ≤ 3 × 10^-4, Ta/W ≤ 1, Os/W ≤ 0.06, Ce/W ≤ 0.0075, Nd/W ≤ 3.5 and Sm/W ≤ 5. The intermediate measurement precisions of both standard solutions (NIST SRM 3163 and Alfa Aesar W) and geological reference materials (NOD-A-1) were better than ±0.024‰ (2s). We also obtained a precision of 0.026‰ for a minimum sample loading mass of 5 ng, allowing the analysis of samples with low W contents. Replicated measurements of geological reference materials (AGV-2, BCR-2, BHVO-2, GSP-2, RGM-1, SDC-1, NOD-A-1 and NOD-P-1) yielded δ^186/184W values ranging from 0.017‰ to 0.144‰. The δ^186/184W values of two major tungsten ore minerals (scheelite and wolframite) were reported and compared herein. Scheelites had systematically slightly heavier W isotopic compositions than wolframites, which may reflect differences in the crystal structure. The resolvable variations of stable/mass-dependent W isotopic compositions in rocks and ore minerals make W isotopes a novel tool for studying hydrothermal mineralisation processes and the W cycle of geological reservoirs.

Two clinopyroxene megacrysts, DMP-2 and DMP-3, were collected from Cenozoic alkali basalts in the Hannuoba region of China. They were characterised for major and trace element compositions for in situ microanalysis. EPMA and LA-ICP-MS analyses indicate homogeneity in the element mass fractions in both clinopyroxene samples. Bulk analyses using various techniques (XRF, ICP-OES and solution ICP-MS) also reveal good consistency in their major and trace element data. They, thus, can be used as potential reference materials for elemental in situ microanalysis. Accordingly, element mass fractions are recommended for thirty-two elements.

The lack of analytical techniques for halogens in geological materials is mainly due to the loss of analytes during sample preparation. This study describes a rapid bulk rock digestion method (NH₄F digestion) for determination of the abundances of Cl, Br and I in geological materials by SF-ICP-MS. During high temperature (200–240 °C) digestion, NH₃ released from the decomposition of molten NH₄F can effectively prevent the loss of halogens released from geological samples. Chlorine, Br and I were not lost during NH₄F digestion at 220 °C for 0.25–6 h. The limits of quantitation for NH₄F digestion were 2.8, 0.018 and 0.003 μg g^-1 Cl, Br and I, respectively. Most results for halogens in geological reference materials by NH₄F digestion were in agreement with their certified values, confirming that the high-performance rapid bulk rock NH₄F digestion has sufficient digestion capability to extract Cl, Br and I from rocks, sediments and soils. In comparison, results obtained following acid digestion showed that HNO₃ + HF digestion could effectively extract Br and I from soil and sediment samples, and that HNO₃ acid digestion is only suitable to use for the determination of Br and I in soil samples.

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is used to compare the suitability of four cassiterite (SnO₂) materials (SPG, Yankee, AY-4 and Jian-1), and three matrix-mismatched reference materials (NIST SRM 612, NIST SRM 614 and 91500 zircon) for normalisation of U-Pb and Pb-Pb isotope ratios in cassiterite. The excess variance of ages determined by LA-ICP-MS is estimated to be ±0.33% for ²⁰⁷Pb/²⁰⁶Pb vs. ²⁰⁸Pb/²⁰⁶Pb isochron ages and ± 1.8% and for U-Pb ages. Incorporation of this excess variance in cassiterite ages is necessary for realistic uncertainties. ²⁰⁷Pb-²⁰⁶Pb ages are advantageous for dating Precambrian cassiterite such as SPG compared with U-Pb ages as matrix effect on instrumental mass fractionation of Pb isotopes are generally considered to be minor. We note minor bias in ²⁰⁷Pb/²⁰⁶Pb vs. ²⁰⁸Pb/²⁰⁶Pb isochron ages (~ 0.6%) when using either the NIST SRM 614 or 91500 zircon reference materials and emphasise the requirement for uncertainty propagation of all sources of error and reference materials with comparable U and Pb mass fraction to the cassiterite. The ²³⁸U/²⁰⁶Pb isotopic ratios from normalisation to matrix-mismatched reference materials show varied results, which emphasises the need to use matrix-matched reference materials for calculating U-Pb ages. When cross-calibrated against each other, LA-ICP-MS U-Pb ages of the ca. 1535 Ma SPG, ca. 245 Ma Yankee and ca. 155 Ma Jian-1 cassiterites are all consistent with their ID-TIMS values.

Reference materials (RMs) with well-characterised composition are necessary for reliable quantification and quality control of isotopic analyses of geological samples. For in situ Rb-Sr analysis of silicate minerals via laser ablation inductively coupled plasma tandem mass spectrometry (LA-ICP-MS/MS) with a collision/reaction cell, there is a general lack of mineral-specific and matrix-matched RMs, which limits wider application of this new laser-based dating technique to certain minerals. In this work, pressed nano-powder pellets (NP) of four RMs, GL-O (glauconite), Mica-Mg (phlogopite), Mica-Fe (biotite) and FK-N (K-feldspar), were analysed and tested for in situ Rb-Sr dating, complemented by isotope dilution (ID) MC-ICP-MS Rb-Sr analyses of GL-O and Mica-Mg. In addition, we attempted to develop alternative flux-free and fused ‘mineral glasses’ from the above RMs for in situ Rb-Sr dating applications. Overall, the results of this study showed that among the above RMs only two NP (Mica-Mg-NP and GL-O-NP) were suitable and robust for in situ dating applications. These two nano-powder reference materials, Mica-Mg-NP and GL-O-NP, were thus used as primary RMs to normalise and determine Rb-Sr ages for three natural minerals: MDC phlogopite and GL-O glauconite grains, and also Mica-Fe-NP (biotite). Our in situ analyses of the above RMs yielded Rb-Sr ages that are in good agreement (within 8%) of published ages, which suggests that both Mica-Mg-NP and GL-O-NP are suitable RMs for in situ Rb-Sr dating of phlogopite, glauconite and biotite. However, using secondary RMs is recommended to monitor the quality of the obtained ages.

New zircon reference materials for in situ zircon radiogenic Hf isotope and stable Zr isotopic determinations made by laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) are required due to high data productivity and consequently high reference material consumption rate. This study examines a new natural zircon for Zr isotope ratios by double spike thermal ionisation mass spectrometry (TIMS), and for Hf isotopes by bulk solution nebuliser (SN)-MC-ICP-MS with both Zr and Hf determined by LA-MC-ICP-MS. A total of five zirconium isotope measurements from drilled zircons, determined by TIMS, yield a mean δ^94/90Zr_IPGP-Zr value of -0.09 ± 0.06‰ (2s). Five and eight hafnium isotope measurements for powders from the drilled zircons and Ban-1-4 by SN-MC-ICP-MS, yield mean ¹⁷⁶Hf/¹⁷⁷Hf ratios of 0.282985 ± 0.000011 (2s) and 0.282982 ± 0.000007 (2s), respectively. The mean δ^94/90Zr_IPGP-Zr value and ¹⁷⁶Hf/¹⁷⁷Hf ratio determined by LA-MC-ICP-MS analyses are -0.06 ± 0.09‰ (2s, n = 504) and 0.282985 ± 0.000035 (2s, n = 327), respectively. The isotopic homogeneities suggest that the Ban-1 zircon is a suitable reference material for microbeam Zr and Hf isotopic measurements.

This GGR Bibliographic Review is a survey of approximately 5200 geoanalytical publications for the year 2021. Selected articles, numbering over 340, containing measurement results for relevant geological and environmental reference materials are listed with individual summaries of target analytes, relevant reference materials and producers. A brief summary of a selection of these publications is included that highlights notable developments in geoanalytical studies, newly developed or characterised RMs, and new datasets of established reference materials that have been re-analysed using improved or state-of-the-art measurement techniques.

Zircon geochemistry can vary over micrometre scales; therefore, natural reference materials need to be well characterised before being used to calculate trace element mass fractions in unmeasured samples. Moreover, reference material homogeneity needs to be ensured with the accelerating rate of geoanalytical developments to map mineral chemistry at increasingly finer scales. Here, we investigate trace element zoning in four widely used zircon reference materials: 91500, Mud Tank, Temora and Plešovice, as well as zircon crystals from the Mount Dromedary/Gulaga Igneous Complex, Australia. Sub-micrometre resolution focused ion beam scanning electron microscope (FIB-SEM) based time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 5 μm resolution LA-ICP-MS mapping show that trace elements are zoned in all reference materials, though 91500 exhibited the least zonation. We demonstrate that FIB-SEM-based ToF-SIMS can rapidly resolve variations in trace elements (e.g., U, Th, Sc, Y, Gd, Dy, Yb and Li) at sensitivities down to the μg g^-1 level with a spatial resolution of 195 nm for areas 100 × 85 μm to 959 × 828 μm. Zircon 91500 is recommended for future quantitative analyses provided that (1) the spatial distribution of elements is imaged before analysis of unknown samples and (2) it is used in conjunction with a doped glass as the primary reference material.