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Precise and accurate determination of major components in alkali silicate glasses provides critical information concerning element distribution, petrogenesis and magmatic evolution. However, as one of the most important in situ microanalytical technologies, the application of electron probe microanalysis (EPMA) was limited by the time-dependent loss of X-ray intensity of alkali ions (especially Na) during electron beam bombardment on alkali silicate glasses. In this study, an optimized analytical method was developed using a JEOL JXA 8100 EPMA, aiming to get a long enough incubation duration suitable for accurate analysis of major element mass fractions. The optimal analytical conditions were determined as follows: 15 kV accelerating voltage, 2 nA beam current, 20 μm beam diameter, 40 s peak counting time, Na and K analyzed with top priority, time-saving mode with no additional detector movement and no peak search functioned. The availability of this low beam current density condition (6.37 × 10−3 nA μm−2) to 24 anhydrous reference glasses, with their compositions covering the entire spectrum from the ultramafic to highly siliceous range, was verified by the good agreement of the EPMA measured data with their GeoReM preferred values. Similarly, the methodology presented here is also suitable for analysis of hydrous glasses with H2O contents up to approximately 9 wt%, accompanied by no obvious Na loss found and no complicated mathematical corrections needed, and therefore can be used for the estimation of H2O contents in H2O-rich (>1 wt%) geological glasses by the difference method. Despite its analytical accuracy and precision (>0.5 wt%) not better than those of SIMS and FTIR, EPMA can be used as a substitute technique for H2O determination with its main advantages of excellent spatial resolution (down to 5–10 μm) and analytical convenience, especially for small melt inclusions or tiny experimental quench products, and the case with no appropriate calibration standards or no reported extinction coefficients available for those compositions of interest. In daily application, our optimized method is low cost and easy to implement and can achieve comparable precision and detection limits with acceptable efficiency (∼4–5 min/point for ten major elements) relative to routine analysis conditions. [ABSTRACT FROM AUTHOR]

Strontium isotopes are applied to a wide range of scientific fields and to different types of materials, providing valuable information foremost about provenance and age, but also on diagenetic processes and mixing relationships between different Sr reservoirs. The development of in situ analytical techniques, such as laser ablation ICP-MS, has improved our understanding of Sr isotope variability in several fields of application, because of the possibility to discriminate small-scale changes and their spatial distribution. However, large outputs of Sr isotope data are produced by laser ablation MC-ICP-MS systems, which necessitate multiple offline steps to correct and assess the data. This requires the availability of simple and user-friendly tools, easily manageable by non-specialists too. With this in mind, we developed SrDR, an Excel-based interactive data reduction spreadsheet ('SrDR', Sr-Data-Reduction) for the processing of Sr isotopes measured by LA-MC-ICP-MS. The SrDR spreadsheet is easily customizable (a) to meet user-specific analytical protocols, (b) for different instruments (i.e. Nu plasma vs. Neptune), and (c) for diverse target materials (e.g. rare earth element enriched or depleted samples). We also include several examples relevant to low and high temperature geochemistry fields – a fossil tooth, a modern seashell, a speleothem sample and plagioclase crystals – to show how different sample materials are corrected for different interfering masses. [ABSTRACT FROM AUTHOR]

Diagenetic alteration of fossil reef corals may have severe effects on the reliability of 230Th/U-ages. The widely applied criteria introduced to test for the reliability of coral 230Th/U-ages are often not sufficient to identify all altered ages. The combination of 230Th/U- with 231Pa/U-dating has been suggested as a promising method to identify altered ages. Furthermore, 226Ra/230Th ratios can provide information about the diagenetic history during the last 10 000 years. Here we present a method to chemically separate U, Th, Pa and Ra from the same aliquot of a carbonate sample. The isotope ratios of our mixed U–Th–Pa–Ra spike are calibrated using a secular equilibrium material treated in the same way as the samples during chemical separation and mass spectrometric analysis. This approach does not only circumvent corrections for the radioactive decay of the short-lived 233Pa spike, but also enables us to estimate the reproducibility of the spike calibration. The relative standard deviation (RSD) of the spike ratios is 0.27% for 229Th/236U, 4.2% for 228Ra/236U and between 0.6 and 4.0% for 233Pa/236U. The RSDs of the final ratios are 1.2% for 231Pa/235U and 3.4% for 226Ra/230Th. We assess the individual sources of uncertainty (e.g., mass spectrometric corrections, counting statistics, and spike calibration) in detail and quantify their contribution to the total uncertainties of the final isotope ratios. Most corrections contribute only moderately to the final uncertainties. However, in the case of a large abundance of natural isotopes in the spike, this correction can have a large influence on both the ratios and their uncertainties. Another parameter affecting the final uncertainties and the reproducibility of the method is the sample size and, thus, the concentration of the natural isotopes. This discussion provides useful guidelines for future applications and can be adjusted to the individual requirements of a specific user. [ABSTRACT FROM AUTHOR]

We applied three different LA systems (213 nm nanosecond solid state, 193 nm nanosecond excimer, and 200 nm femtosecond laser) coupled to a quadrupole ICP-MS or a sector field ICP-MS, respectively, for the analysis of different sulfide minerals (pyrrhotite, chalcopyrite, and sphalerite). Ablation craters were investigated via back-scattered electron (BSE) images to compare the amounts of melt produced, and fractionation factors were calculated to determine the degree of down-hole fractionation. Our results show significant differences in melting between the three LA systems. While samples show massive melting when using the ns systems, no melting has been observed utilizing the fs laser. Fractionation factors for a variety of elemental pairs indicate the absence of down-hole fractionation even at the highest melt production. The extent of melting of different sulfide specimens is independent of melting temperatures of these materials. Although no down-hole fractionation has been observed, Fe/S fractionation as calculated from sensitivities deviate among pyrrhotite and chalcopyrite when applying the 193 nm ns and 200 nm fs systems. Analyses of synthetic pyrrhotite with known PGE concentrations using the 200 nm fs LA system yielded moderately precise and accurate concentration data (3–4%; 4–14% 2SD) utilizing sulfide as the external reference material. Application of NIST610 as the reference material improved the precision to 1.4–2.4% 2SD and the deviation from reference values to 5–7%. [ABSTRACT FROM AUTHOR]