To expand the newly developed ARM glasses as reference materials for in situ microanalysis of isotope ratios and iron oxidation state by a variety of techniques such as SIMS, LA‐MC‐ICP‐MS and EPMA, we report Li‐B‐Si‐O‐Mg‐Sr‐Nd‐Hf‐Pb isotope data and Fe 2+ /ΣFe ratios for these glasses. The data were mainly obtained by TIMS, MC‐ICP‐MS, IR‐MS and wet‐chemistry colorimetric techniques. The quality of these data was cross‐checked by comparing different techniques or by comparing the results from different laboratories using the same technique. All three glasses appear to be homogeneous with respect to the investigated isotope ratios (except for B in ARM‐3) and Fe 2+ /ΣFe ratios at the scale of sampling volume and level of the analytical precision of each technique. The homogeneity of Li‐B‐O‐Nd‐Pb isotope ratios at the microscale (30–120 μm) was estimated using LA‐MC‐ICP‐MS and SIMS techniques. We also present new EPMA major element data obtained using three different instruments for the glasses. The determination of reference values for the major elements and their uncertainties at the 95% confidence level closely followed ISO guidelines and the Certification Protocol of the International Association of Geoanalysts. The ARM glasses may be particularly useful as reference materials for in situ isotope ratio analysis.
A new natural zircon reference material SA01 is introduced for U‐Pb geochronology as well as O and Hf isotope geochemistry by microbeam techniques. The zircon megacryst is homogeneous with respect to U‐Pb, O and Hf isotopes based on a large number of measurements by laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and secondary ion mass spectrometry (SIMS). Chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA‐ID‐TIMS) U‐Pb isotopic analyses produced a mean 206 Pb/ 238 U age of 535.08 ± 0.32 Ma (2 s , n = 10). Results of SIMS and LA‐ICP‐MS analyses on individual shards are consistent with the TIMS ages within uncertainty. The δ 18 O value determined by laser fluorination is 6.16 ± 0.26‰ (2 s , n = 14), and the mean 176 Hf/ 177 Hf ratio determined by solution MC‐ICP‐MS is 0.282293 ± 0.000007 (2 s , n = 30), which are in good agreement with the statistical mean of microbeam analyses. The megacryst is characterised by significant localised variations in Th/U ratio (0.328–4.269) and Li isotopic ratio (−5.5 to +7.9‰); the latter makes it unsuitable as a lithium isotope reference material.
The isotope dilution (ID) method, owing to its high precision, is extensively used for the determination of element mass fractions in a wide range of natural samples. One of the prerequisites of the ID method is knowledge of the isotopic composition of an enriched spike, which is often challenging to accurately determine. In this study, we employ a regression mass bias correction model to accurately and precisely measure the isotopic composition of an enriched Hf spike (Lot No. 159293, Oak Ridge National Laboratory). A NIST SRM 3134 Re solution, whose isotopic composition was calibrated by an NRC IRIS‐1 Ir isotope standard, was used to calibrate the isotopic composition of the Hf spike. The obtained ratios of 176 Hf/ 177 Hf, 179 Hf/ 177 Hf and 180 Hf/ 177 Hf were 0.2406 ± 0.0005 ( u, k = 1), 2.8620 ± 0.0005 ( u, k = 1) and 384.65 ± 0.05 ( u, k = 1), respectively, which meet the required precision levels for Hf isotopes in the application of the ID method. The combined uncertainties of the calibrated Re and Hf isotope ratios were evaluated using a Monte Carlo method, in which the uncertainty of the primary calibrator (IRIS‐1, 193 Ir/ 191 Ir = 1.6866 ± 0.0005, u , k = 1) was also taken into consideration. The precision of Hf spike was improved significantly compared with the SSB and C‐SSBIN methods. To the best of our knowledge, this is the first report of isotope ratio calibration in an enriched spike using the regression model. The precisely calibrated spike can lower the uncertainty of the Hf mass fraction significantly, thereby increasing the accuracy of the Lu‐Hf chronometer.
Lithium isotopes in carbonate rocks and minerals can serve as important tools for assessing palaeoclimates and palaeoenvironments. However, carbonate bulk rock samples are commonly mixtures of carbonate and silicate minerals, which require the complete digestion of the carbonate without digesting the silicate. Additionally, the low Li content (ng g −1 level) in carbonates provides an additional challenge. Hence, despite their wide applications, few carbonates have had their δ 7 Li values characterised, particularly carbonate reference materials, which hinders comparisons of Li isotope measurement results obtained in different laboratories and the further application of Li isotopes in geological studies. This study aimed to provide precise and accurate δ 7 Li values for carbonate reference materials based on an evaluation of sample leaching and the Li purification method for carbonates, as well as the adoption of soft extraction and 10 12 Ω amplifiers to increase the intensity/blank ratio and matrix effect on Li isotope measurement. The precision and accuracy of the proposed procedure were verified by analysing synthetic carbonate samples and mono‐elemental Li solutions. With the developed method we provide δ 7 Li values for eleven carbonate reference materials with a precision of ~ 0.4‰. The accuracy of the δ 7 Li values was validated using the standard addition method.
LA-ICP-MS and LA-MC-ICP-MS have been the techniques of choice for achieving accurate and precise element content and isotopic ratio, the state-of-the-art technique combines the advantages of low detection limits with high spatial resolution, however, the analysis accuracy and precision are restricted by many factors, such as sensitivity drift, elemental/isotopic fractionation, matrix effects, interferences and the lack of sufficiently matrix-matched reference materials. Thus, rigorous and suitable calibration and correction methods are needed to obtain quantitative data. This review systematically summarized and evaluated the interference correction, quantitative calculation and sensitivity correction strategies in order to provide the analysts with suitable calibration and correction strategies according to the sample types and the analyzed elements. The functions and features of data reduction software ICPMSDataCal were also outlined, which can provide real-time and on-line data reduction of element content and isotopic ratios analyzed by LA-ICP-MS and LA-MC-ICP-MS.
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