Microanalytical techniques, such as LA-ICPMS, LA-MC-ICPMS, SIMS, have become important tools for in-situ isotope analysis. Yet, the lack of widely available geological reference glasses has made interlaboratory comparisons and assessment of analytical accuracy difficult or even impossible in many cases. Jochum et al. (2000) prepared eight geological MPI-DING glasses of different natural composition (from ultramafic to highly siliceous composition) for the purpose of providing reference materials for in-situ microanalytical work. Recently, reference values for up to 74 major and trace elements have been determined following the recommendations of the IAG (Jochum et al., 2006). The isotopic composition of H, Li, B, O, Ca, Sr, Nd, Hf and Pb was determined in the MPI-DING reference glasses by high-precision mass spectrometric (e.g., TIMS, MC-ICPMS) using large sample amounts and by microanalytical (LA-ICPMS, LA-MC-ICPMS, SIMS) techniques. The precision of the bulk techniques is significantly higher than that of the microanalytical techniques. However, the microanalytical techniques have the advantage of high spatial resolution and fast sample preparation. The boron isotope composition was determined using TIMS and LA-MC-ICPMS. LA-MC-ICPMS data for the MPI- DING glasses agree with the TIMS data at the 2 σ level. The MPI-DING glasses range from δ 7Li of 2.0 to 17.1 ‰ LSVEC. The uncertainties of MC-ICPMS measurements compared to SIMS data are smaller, owing to the larger amount of Li measured. Some small local heterogeneity in Li isotopes could be observed using SIMS. Highly precise Sr and Nd isotope analyses were performed for each MPI-DING glass using TIMS. Recently, Sr isotopes have also been determined by LA-ICPMS in the low-Sr (30 - 300 ppm) glasses. The 87Sr/86Sr ratios for KL2-G (0.7038 ± 0.0002), ML3B-G (0.7035 ± 0.0003) and GOR128-G (0.7067 ± 0.0007) agree within 0.01 - 0.04 % with the TIMS data. Lead isotope ratios have been determined by TIMS, MC-ICPMS, solution ICPMS and LA-ICPMS. LA-ICPMS is able to determine 208Pb/206Pb and 207Pb/206Pb ratios in the low-Pb (1 - 10 ppm) MPI-DING glasses with a precision of about 0.05 - 0.2%. Possible heterogeneities of Pb isotopes are found by high-precision TIMS and MC-ICPMS measurements using different glass chips. However, the differences are lower than the reproducibility obtained from microanalytical techniques. Because the amount of data for reference materials has significantly increased in recent years, there is a need for a database that contains published analytical data together with important metadata (e.g., uncertainty, analytical technique, laboratory) in a form in which it can be accessed readily by geochemists. Jochum et al. (2005) have therefore developed the GeoReM database (http://georem.mpch-mainz.gwdg.de) for reference materials and isotopic standards of geochemical, mineralogical and environmental interest. At present, GeoReM contains ca. 1500 reference materials (including the MPI-DING glasses) and 13500 analyses from about 2100 publications.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 1040 Radiogenic isotope geochemistry;
- 1041 Stable isotope geochemistry (0454;
- 1065 Major and trace element geochemistry