Geostandards and Geoanalytical Research最新文献

Analytical techniques are essential in investigating the unique features of extra-terrestrial geomaterials, and the use of in situ analytical tools is becoming increasingly common, as it facilitates a quick initial bulk chemical analysis, identification and classification. In this work, a handheld laser-induced breakdown spectroscopy (hLIBS) instrument has been used to identify the qualitative and quantitative composition, and generate compositional micro-maps, of a suite of iron meteorite samples representative of the different chemical and structural classes by analysing the spectra released from the plasma formed by the laser impact. Furthermore, the analytical performance of hLIBS was compared with that of portable X-ray fluorescence spectrometry (pXRF). The analytical precision and accuracy of the calibration curves previously built in the laboratory for a set of certified reference metal alloys was assessed, so that the same protocol could be used to measure those of the investigated iron meteorites. A good agreement was achieved between hLIBS and reference data in the quantitative estimate of the elements Fe, Ni, Co and Cu. An attempt to quantify Ga by LIBS in two classified iron meteorites was also successful.

Magnesium isotope ratios in carbonate rocks and minerals play an important role in tracing geological and biological processes. We report δ²⁶Mg_DSM3 values for the first time in ten carbonate reference materials (GBW07865, GBW07114, GBW(E)070159, GBW07136, GBW07108, GBW03109a, GBW07120, GBW07214a, IAEA-B-7 and IAEA-CO-8) with calcium to magnesium mass ratios around 1300 g g⁻¹ and ultra-low Mg mass fractions of 295 μg g⁻¹. A combination of AG MP-50 (100–200 mesh) and AG 50W-X12 (200–400 mesh) resins for the matrix extraction and multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) were used for the isotopic measurements. This measurement procedure is applicable to materials with high and low Mg mass fractions (e.g., carbonates, lunar highlands anorthosites, ice core). It was validated using various types of reference material. In-house synthetic solutions with 1000 and 1300 g g⁻¹ [Ca]/[Mg] mass ratios yielded δ²⁶Mg_DSM3 values at 2s = ±0.05‰ (n = 62), -4.89‰ and -4.89‰, respectively, indistinguishable from those of the pure Mg solutions, at -4.91‰. δ²⁶Mg_DSM3 values in well characterised carbonatite and carbonate reference materials (such as JDo-1, COQ-1, GBW07133, GBW07217a and GBW07129), with varying MgO and CaO mass fractions, were in agreement with literature values.

Multi-element quantification in small amounts of material and in situ measurements at the micrometre scale are essential aspects of geological sample investigation. A direct and rapid simultaneous multi-elemental determination of metals in crude oil samples was carried out by combining direct laser ablation of the oil inserted in silica capillaries with inductively coupled plasma-mass spectrometry. The accuracy of LA-ICP-MS determination was demonstrated by analysing CONOSTAN reference material oils, certified for multiple elements, and by comparing LA-ICP-MS measurement results with those obtained by ICP-OES using microwave-assisted sample digestion. The results obtained by both methods were in agreement with certified values. The LA-ICP-MS method showed an adequate precision with a mean relative standard deviation of less than 10% for multi-element determination, and was sufficiently sensitive to determine the majority of elements. LA-ICP-MS was also applied to the determination of elements in crude oils of different origins. LA-ICP-MS is a good alternative method allowing the determination of elements in organic fluids (oil and bitumen) in shorter times, involving less material consumption, smaller test portion size and with higher throughput compared with protocols using, for instance, sample digestion. It validates the possible application of metal analysis in hydrocarbon-containing fluid inclusions for metallogenic purposes.

Garnet U-Pb dating by laser ablation-inductively coupled plasma-mass spectrometry requires the development of matrix-matched reference materials of variable chemistry and U mass fraction for accurate analysis. Additional calibration of existing primary reference materials is also justified based on the relatively poor calibration of some of the widely available primary reference materials that are currently utilised by the geoscience community. We present a micro sampling workflow combined with a refined ID-TIMS methodology for the generation of high precision (~ 0.1%) U-Pb dates from domains within garnet single crystals. Using this workflow, we calibrated two new natural andradite reference materials, the Jumbo andradite (And₉₉; 110.34 ± 0.03 (0.04) [0.13] Ma, n = 7, MSWD = 1.21) and the Tiptop andradite (And₈₇; 209.57 ± 0.11 (0.13) [0.26] Ma, n = 6, MSWD = 1.39). We also present additional calibration of the widely utilised Willsboro-Lewis andradite primary reference material (And₉₀; 1024.7 ± 9.5 (9.6) [9.6] Ma (2s; overdispersed), n = 6). Wafers of the Jumbo and Tiptop andradite reference materials are available from the authors upon request.

In situ garnet Lu-Hf geochronology has the potential to revolutionise the chronology of petrological and tectonic processes, yet there is a paucity of well-characterised reference materials to account for laser-induced matrix-dependant elemental fractionation. Here, we characterise two reference garnets GWA-1 (Lu ~ 7.0 μg g⁻¹) and GWA-2 (Lu ~ 8.5 μg g⁻¹) for in situ garnet Lu-Hf geochronology. Isochron ages from isotope dilution Lu-Hf analyses yield crystallisation ages of 1267.0 ± 3.0 Ma with initial ¹⁷⁶Hf/¹⁷⁷Hf_i of 0.281415 ± 0.000012 (GWA-1), and 934.7 ± 1.4 Ma with ¹⁷⁶Hf/¹⁷⁷Hf_i of 0.281386 ± 0.000013 (GWA-2). In situ Lu-Hf analyses yield inverse isochron ages up to 10% older than the known crystallisation age due to matrix effects between garnet and reference glass (NIST SRM 610) under different instrument tuning conditions. This apparent age offset is reproducible for both materials within the same session and can be readily corrected to obtain accurate ages. Our results demonstrate that GWA-1 and GWA-2 are robust reference materials that can be used to correct for matrix-analytical effects and also to assess the accuracy of in situ Lu-Hf garnet analyses across a range of commonly encountered garnet compositions.

We have established a method for the simultaneous measurement of element abundances and boron isotopic compositions of bulk-rock silicate samples by laser ablation coupled to two different ICP-MS instruments. Fifteen silicate reference materials were prepared as micro-particulate pressed powder pellets (MP) for analysis. Approximately 1/5th of the ablated material was transported to a single-collector ICP-MS for elemental measurement, while 4/5ths were sent to a multi-collector ICP-MS for boron isotope ratio measurement. Compositions of different milling materials (agate, zirconium oxide, tungsten carbide, sintered corundum and silicon nitride) were measured for the evaluation of potential contamination during sample preparation. Determined element mass fractions are in agreement with literature values within ±20%. For boron isotope ratios, the matrix-dependent background elevation across the m/z from 9.9 to 11, and the effect of ablation mass was quantified. Measured δ¹¹B values of most reference materials are consistent with literature values within ±1‰. The intermediate measurement precision is ±0.3‰ for JB-2 with 30 μg g⁻¹ B and ±0.4‰ for JA-2 with 21 μg g⁻¹ B. A publically available, web-based streamlit app was developed for data processing (https://zenodo.org/doi/10.5281/zenodo.11150471). This paves the way for combined, accurate and precise elemental and boron isotope ratio measurements of geological materials.

A robust analytical method is presented here, for measurements of Sn isotope variations with high precision using a multi-collector inductively coupled plasma-mass spectrometer (MC-ICP-MS). A silicate rock dissolution procedure was used, together with means to remove organic matter introduced by the resin during ion-exchange chromatography. The two-stage ion exchange chromatography efficiently isolates Sn from the matrix and isobarically interfering elements, from samples with variable Sn mass fractions (~ 0.03 to 7 μg g⁻¹). A double spike technique was also implemented to correct any secondary mass bias induced during sample processing and isotope ratio measurements. An intermediate precision (2s) of ± 0.47 was obtained for ε^122/118Sn (using internal normalisation; n = 70 over a period of 29 months), ± 0.021‰ for δ^122/118Sn (using double spike; n = 176 over a period of 29 months) and ± 0.059‰ for δ^122/118Sn (using Sb doping; n = 34 over a period of 4.5 months) for the Sn standard solution, NIST SRM 3161a (Lot# 140917). The δ^122/118Sn_{NIST SRM 3161a} of eleven geological reference materials are reported for the first time (BIR-1a, BRP-1, DTS-2b, ECRM 782-1, JP-1, OKUM, QLO-1a, RGM-2, SGR-1b, STM-2 and UB-N), with five others (AGV-2, BCR-2, BHVO-2, GSP-2 and W-2a) showing similar results to previous studies, generally with improved precision. The intermediate precision (2s) of replicate dissolutions of ten RMs (AGV-2, BCR-2, BHVO-2, BIR-1a, DTS-2b, GSP-2, OKUM, SGR-1b, STM-2 and W-2a) varied from 0.003 to 0.054‰. Typical repeatability precision (2SE) of individual measurements of these ten RMs over multiple measurement sessions varied from 0.031 to 0.297‰ (with ¹²⁰Sn⁺ beam intensity < 2.37 V) and 0.017 to 0.025‰ (with ¹²⁰Sn⁺ beam intensity > 2.37 V).

Calibrated isotope ratio measurements underpin numerous areas of scientific enquiry. Isotope measurement results rely on reference materials in order to correct instrumental isotopic fractionation, a bias induced by all mass spectrometers. The reference values assigned to these materials are typically obtained using gravimetric mixtures of separated isotopes but such experiments are costly and thus rarely cross-examined. Here we advance the concept of linking measurements of various isotope systems to provide a cost-effective way to assess the reliability of the values assigned to isotopic primary standards. Using MC-ICP-MS, we apply this workflow to examine the consistency of a couple of long-standing isotopic primary standards of copper, nickel and zinc. Our measurement results of the reference materials that define the isotope ratios and consequently the atomic weights of zinc and nickel, A_r(Zn, IRMM-3702) = 65.3604 ± 0.0023 (95% confidence interval) and A_r(Ni, NIST SRM 986) = 58.6979 ± 0.0010 (95% confidence interval), show zinc to be 15-sigma lighter and nickel 16-sigma heavier than their certified values. These discrepancies are suggestive of a wider reproducibility crisis surrounding isotopic standards and a further cross-examination of isotope ratios associated with primary reference materials is likely to identify yet-unrecognised biases for many other elements of the Periodic Table leading to improvements of the overall reliability of research conclusions that relies on them.

In situ ⁸⁷Sr/⁸⁶Sr microanalysis in bioapatite using laser ablation (LA-)MC-ICP-MS is an essential tool for provenance studies, as enamel tissue build-up records the regional Sr isotopic composition of ingested food and water sources. Several factors hamper the acquisition of reliable and precise ⁸⁷Sr/⁸⁶Sr data: isobaric interferences, elemental and isotopic fractionation of Rb and Sr, and the lack of certified reference materials. Here we thoroughly characterise several teeth from Carcharinus leucas (Bull shark) for the spatial distribution of Sr and Rb mass fraction by LA-ICP-Q-MS, and their ⁸⁷Sr/⁸⁶Sr ratio by solution MC-ICP-MS, MC-TIMS and LA-MC-ICP-MS, and which were used subsequently as a reference material during laser ablation measurement of Sr isotope ratios in bioapatite. We establish a protocol to estimate the ⁸⁵Rb/⁸⁷Rb mass bias from the analysis of shark teeth that demonstrates that the common assumption of equal Sr and Rb instrument induced fractionation can lead to a systematic bias in ⁸⁷Sr/⁸⁶Sr isotope ratios. Using the shark teeth as an "external" reference material to measure β_Rb yielded ⁸⁷Sr/⁸⁶Sr compositions in unknown samples that are within approximately -42 ppm to +66 ppm of expected values, instead of approximately -50 ppm to +190 ppm if assuming β_Rb = β_Sr. Finally, this methodology was tested on fossil gomphotherid (Rhynchotherium sp.) enamel, allowing us to make preliminary inferences about its palaeobiogeography.

We present a new set of reference materials, the ND70-series, for in situ measurement of volatile elements (H₂O, CO₂, S, Cl, F) in silicate glass of basaltic composition. The materials were synthesised in piston cylinders at pressures of 1 to 1.5 GPa under volatile-undersaturated conditions. They span mass fractions from 0 to 6% m/m H₂O, from 0 to 1.6% m/m CO₂ and from 0 to 1% m/m S, Cl and F. The materials were characterised by elastic recoil detection analysis for H₂O, by nuclear reaction analysis for CO₂, by elemental analyser for CO₂, by Fourier transform infrared spectroscopy for H₂O and CO₂, by secondary ion mass spectrometry for H₂O, CO₂, S, Cl and F, and by electron probe microanalysis for CO₂, S, Cl and major elements. Comparison between expected and measured volatile amounts across techniques and institutions is excellent. It was found however that SIMS measurements of CO₂ mass fractions using either Cs⁺ or O⁻ primary beams are strongly affected by the glass H₂O content. Reference materials have been made available to users at ion probe facilities in the US, Europe and Japan. Remaining reference materials are preserved at the Smithsonian National Museum of Natural History where they are freely available on loan to any researcher.