Geostandards and Geoanalytical Research最新文献

The use of ID-MS (ID-TIMS/MC-ICP-MS) techniques to characterise reference materials (RM) with high Rb/Sr and ⁸⁷Sr/⁸⁶Sr for in situ LA-ICP-MS-MS Rb-Sr geochronology is highly important. However, there is a lack of well-characterised RMs with high Rb/Sr and ⁸⁷Sr/⁸⁶Sr ratios to effectively monitor data quality for ID-TIMS/MC-ICP-MS Rb-Sr geochronology. In this study, a pegmatite RM, OU-9, was comprehensively characterised using ID-TIMS/MC-ICP-MS techniques. Measurements undertaken on OU-9 yielded mass fractions of 2494 ± 22 μg g^-1 for Rb, 36.05 ± 0.25 μg g^-1 for Sr, as well as isotope ratios of 832.4 ± 5.2 for ⁸⁷Rb/⁸⁶Sr and 32.60 ± 0.19 for ⁸⁷Sr/⁸⁶Sr. Despite the presence of inhomogeneity within and between RM sachets, regarding Rb-Sr isotope systematics at sampling scales of ~ 10 mg and even 0.2 g, ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr values derived from the analyses align well along the reference isochron. This alignment yields a model age of ~ 2650 Ma with an initial ⁸⁷Sr/⁸⁶Sr of ~ 1.2. We advocate that OU-9 could serve as a potential RM for ID-TIMS/MC-ICP-MS Rb-Sr data quality control for materials characterised by high ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr ratios. The data quality of individual measurement results can be assessed based on their fit to the correlation line.

A rapid, minimally destructive method for in situ determination of Sr isotope ratios (⁸⁷Sr/⁸⁶Sr) using short-pulse laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) coupled with linear regression calibration is presented. The ablation lasts only one second, causing minimal surface damage (~ 7 μm depth, 60 μm diameter). A carbonate matrix reference material for Sr isotope measurement (GIC-P, containing approximately 470 μg g⁻¹ Sr), fabricated from pressed pearl nanopowder, has been developed for data quality control and validation. Analysis of GIC-P using the proposed short-pulse LA-MC-ICP-MS method yielded results consistent with thermal ionisation mass spectrometry values. This method is ideal for analysis of valuable jewellery samples, as it ensures minimal destruction, high throughput, and cost efficiency while maintaining accuracy and precision, with intermediate precision quantified at better than 0.0004 (2s). When applied to market samples originating from China, Japan, French Polynesia and the South Pacific, the method confirms that saltwater pearls exhibit ⁸⁷Sr/⁸⁶Sr ratios consistent with modern seawater (~ 0.7092), whereas freshwater pearls show higher and more variable ratios (0.7102–0.7135 in this study), reflecting their growth environments in the freshwater of the middle and downstream regions of the Yangtze River, China. This distinct isotopic difference provides a reliable geochemical tool for differentiating between saltwater and freshwater pearls.

A new gem-quality zircon reference material, S513, was developed for in situ microbeam U-Th-Pb, (U-Th)/He geochronology and Hf-O isotope measurement. The well-cut gem-quality zircon weighed 51.3 carats. Its U, Th, Pb and Hf mass fractions were 924 ± 64.6 μg g⁻¹ (2s), 89.6 ± 3.92 μg g⁻¹ (2s), 119 ± 5.20 μg g⁻¹ (2s) and 8259 ± 244 μg g⁻¹ (2s), respectively. Imaging results from LA-ICP-ToF-MS analysis showed homogeneous distribution of elements in S513. The Th-corrected weighted mean ²⁰⁶Pb/²³⁸U, ²⁰⁷Pb/²³⁵U and ²⁰⁷Pb/²⁰⁶Pb ratios of S513 zircon from eight ID-TIMS analyses are 0.090955 ± 0.000019 (2s, MSWD = 0.22, n = 8), 0.73873 ± 0.00023 (2s, MSWD = 0.19, n = 8) and 0.058934 ± 0.000008 (2s, MSWD = 0.35, n = 8), respectively. The Th-corrected weighted mean ²⁰⁶Pb/²³⁸U age obtained from chemical abrasion-isotope dilution-thermal ionisation mass spectrometry is 561.18 ± 0.63 Ma (n = 8, 95% conf., MSWD = 0.9), which is recommended as the best age estimate of S513. The weighted mean ²⁰⁶Pb/²³⁸U ages obtained from in situ microbeam analysis (i.e., LA-ICP-MS and SIMS) were 560.8 ± 5.8/10.2 Ma (2s, n = 260) and 562.4 ± 7.2/13.4 Ma (2s, n = 198). The measured weighted mean ²⁰⁸Pb/²³²Th age of S513 from LA analyses was 561.3 ± 3.3/11.7 Ma (2s, n = 86). The U-Pb and Th-Pb ages of S513 obtained with in situ methods showed good agreement with the CA-ID-TIMS results, respectively. The obtained (U-Th)/He age of S513 from thirty-seven aliquots analysed with U-Th isotope dilution method was 420.3 ± 7.6 Ma (2s, MSWD = 0.72). The recommended reference value of Hf isotope ratio was 0.281606 ± 0.000010 (2s, MSWD = 1.4, n = 12) according to the mean ¹⁷⁶Hf/¹⁷⁷Hf ratio acquired with solution MC-ICP-MS analysis. All the LA analyses yielded a mean ¹⁷⁶Hf/¹⁷⁷Hf ratio of 0.281605 ± 0.000008 (2s, MSWD = 0.53, n = 310), which was consistent with the reference value. Laser fluorination analyses yielded mean δ¹⁸O values of S513 were 11.71 ± 0.11‰ (2s, MSWD = 0.25, n = 5). The results obtained with multiple analytical methods show that zircon S513 is homogeneous to 8% (1s) or better for contents of Y, Nb, Ce, Gd, heavy REE, Ta, U, Th, Pb and Hf. Additionally, the homogeneity is observed at 0.12‰ (2s) for U-Pb ages, 1.8% (2s) for (U-Th)/He ages, 0.0036% (2s) for Hf isotopes, and 0.11‰ (2s) for O isotope ratios. Zircon S513 is proposed as a new potential primary calibration or quality control reference material for microbeam U-Th-Pb geochronology and Hf-O isotope measurement.

To meet the demand of reliable copper isotopic data in various scientific research, a new copper isotopic reference material GBW04624 with high purity (99.9996%), sufficient homogeneity and stability was developed in this study. A copper isotope amount ratio of n(⁶⁵Cu)/n(⁶³Cu) = 0.44559 ± 0.00018 (U, k = 2) in GBW04624 was obtained by calibrated mass spectrometry involving two mass bias correction strategies. The uncertainty of property values was evaluated and traceability to the International System of Units (SI) was established. Copper isotope ratios in geological reference materials GBW07105 and BCR-2 were determined relative to both GBW04624 and the internationally recognised copper isotopic reference material NIST SRM 976. The conversion between δ⁶⁵Cu values relative to NIST SRM 976 and GBW04624 was achieved by applying a δ⁶⁵Cu_{GBW04624–NIST SRM 976} value of 0.252 ± 0.015‰ (U, k = 2).

This chapter (Principles and Practice of X-Ray Fluorescence Spectrometry – 2: Wavelength Dispersive and Energy Dispersive Instrumentation) is a contribution to the Geostandards and Geoanalytical Research Handbook of Rock and Mineral Analysis – an online textbook that is a fully revised and updated edition of A Handbook of Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

Chapter 6, Part 2 (from Section 2 of the handbook devoted to techniques for the determination of major and trace elements) deals with XRF wavelength dispersive and energy dispersive spectrometry. Dealing first with WD-XRF, Part 2 discusses its instrumentation, spectrum analysis and routine operating conditions. The following sections on ED-XRF discuss its detectors and their characteristics,  the associated (pulse-processing) electronics, and X-ray interaction with these detectors. Consideration is then given to procedures for ED-XRF spectra analysis, as well as its analysis of silicate rock and mineral materials under routine operating conditions. Further sections cover total reflection XRF (TRXRF) and field portable (PXRF) instrumentation, and statistical procedures relevant to XRF analysis. The chapter also includes a comparison of the WD and ED spectrometer types and of their analytical performance, with emphasis on silicate rock analysis.

We report for the first time Tl isotope ratios for ten geological reference materials (RMs), namely SGR-1b (from the USGS), and GBW07302, GBW07303a, GBW07401a, GBW03104, GBW07103, GBW07109, GBW07110, GBW07111 and GBW07113 (from China). The principal matrix characteristics of these materials range from sediments to igneous rocks, including stream sediment, soil, shale, granite, nepheline syenite, trachyte, granodiorite and rhyolite. Analytically, the procedure we developed includes a sample digestion step, a simplified single-stage anion exchange matrix separation step and measurements by MC-ICP-MS. For sample digestion we compared a dry ashing-based process with an acid digestion method under high-pressure conditions. We observed that the RMs with high organic content (e.g., SGR-1b = ~ 25%) showed very high values of loss on ignition (LOI) (~ 40%) during dry ashing. Moreover, Tl isotopic measurement results were heavier after dry ashing than after application of the high-pressure bomb method. We infer that the combustion conditions in case of large amounts of organic matter are probably the cause of Tl isotopic fractionation effects (preferential evaporation of ²⁰³Tl). We thus recommend the high-pressure bomb method for the sample digestion step. We validated our entire measurement procedure by applying it to well-documented RMs, including GSP-2 (granodiorite), Nod-A-1 (Marine sediment), Nod-P-1 (Marine sediment) and SCo-1 (shale). Our measurement results were in agreement with literature values.

The B isotope systematics (δ¹¹B) in amphibole offer insights into fluid- and melt-dominated processes in the crust-mantle system. We developed an analytical strategy for in situ B isotope determination in amphibole using LA- MC-ICP-MS on material with a B fraction of a few μg g⁻¹ using 10¹³ Ω resistors. Sources of error deriving from matrix effects were evaluated. Two Ca-amphiboles, one from Pargas, Finland (PRG), and another from the Finero Complex (S. Alps, FIN), were characterised as potential reference materials. PRG has a B mass fraction of 6.75 ± 1.10 μg g⁻¹ and a δ¹¹B value of -16.58 ± 0.06‰, while FIN has 3.27 ± 0.68 μg g⁻¹ of B and a δ¹¹B value of -5.90 ± 0.09‰. A standard-sample-standard bracketing method, using USGS BHVO-2G basaltic glass as the bracketing ‘standard’ (calibrator), provided accurate and reproducible in situ δ¹¹B measurements with 2s of ± 2.86‰ (n = 87) for PRG and ± 3.96‰ for FIN (n = 70). These Ca-amphiboles are suitable reference materials to assess accuracy during in situ B isotope determination with LA-MC-ICP-MS. The potential of in situ B isotope determination in Ca-amphibole as a geochemical tool to investigate petrogenetic processes of a well-characterised amphibole-bearing gabbro from the Adamello batholith (C. Alps) has been tested successfully.

This chapter (Analysis of Geological Materials – 1: Sample Preparation Methods) is a contribution to the Geostandards and Geoanalytical Research Handbook of Rock and Mineral Analysis – an online textbook that is a fully revised and updated edition of A Handbook of Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

In Chapter 2, Part 1 (from Section 1 of the handbook dealing with fundamentals of measurement and instrument design) rock sample preparation techniques will be considered in detail (Parts 2 and 3 deal with pre-concentration and separation procedures, and the determination of specific element groups, respectively). Despite some techniques undertaking measurements on solid samples, the need for dissolution remains the preferred method for many modern instrumental measurement principles such as ICP-MS, ICP-AES and TIMS. A solution provides homogeneity and can further be used for separation and pre-concentration, both of which are important for the measurement of low mass fractions in isotope geochemistry. Part 1 first takes an historical view of developments in this field, followed by state-of-the-art assessments of dissolution procedures based on acid attack, decomposition by molten salt fusion, the decomposition of resistant minerals, flux-free fusion, and the use of pressed powder pellets.