Isotopic Constraints on Earth System Processes. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

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0.06 0.05 0.07 0.05 4 Simon and DePaolo (2010) average –0.07 0.05 –0.07 0.06 Carbonatites Laacher See 129OL lava 2007OL lava 4‐7‐08 0.0129000.0000130.000011 –0.39–0.130.05 0.140.130.14 –0.27–0.060.06 0.250.100.10 121 Standards SRM915aSeawater (IAPSO) Seawater (GeoB 9506‐4) –0.950.810.94 0.040.160.04 –0.77–– 0.06–– 111 this study Simon et al. (2017)Bermingham et al. (2018)

      Note: All reported where difference between BSE to SRM915a is 0.95 (Antonelli and Simon, 2020), cf. Simon and DePaolo (2010) saw an intrinsic effect in SRM915a, which leads to ~0.1 per mil increase in measured values reported relative to SRM915a (see text).

      More than four different reference materials are currently used to define δ44Ca (see inter‐conversions in Antonelli & Simon, 2020). These are igneous samples that represent BSE, e.g., unmetamorphosed peridotites, komatiites, and basaltic rocks from Earth and other terrestrial planets, carbonate standard SRM915a, synthetic carbonate standard SRM915b, and modern seawater. In this study, reported values assume BSE = 0.0‰ (reported as deviations from 44Ca/40Ca = 0.0212094 ± 3 and 43Ca/40Ca = 726.840 ± 45; see Simon & DePaolo, 2010). This follows the approach of DePaolo (2004). When multiple measurements were made, the values listed in Table 3.1 are weighted means with uncertainties of two standard errors in the mean and are corrected for age and/or intrinsic 44Ca/40Ca ratio based on measurements reported by Simon et al. (2009). The reported uncertainties are typically less than the 2SD long‐term reproducibility of the SRM915a standard, which is ± 0.14 and ± 0.20‰ for δ44Ca and δ43Ca, respectively. Based on my experience, this is the current resolution of the technique and, therefore, I focus on δ44Ca differences that are greater than ~0.15‰. When only an individual measurement is reported, I assign the 2SD reproducibility of the SRM915a standard.

      3.2.2. Igneous Samples Characterized for Calcium Isotope Composition

Lab Facilities Method 44Ca/40CaBSE‐SRM915a Source
Center for Isotope Geochemistry, University of California at Berkeley DS‐TIMS 0.97 0.07 Simon & DePaolo (2010); this work
Center for Isotope Cosmochemistry & Geochronology, NASA Johnson Space Center DS‐TIMS 0.96 0.04 Simon et al. (2017)
Isotope Research Geo‐ and Cosmochemistry Group, Harvard University DS‐TIMS 0.97 0.04 Huang et al. (2011)
State Key Laboratory of Isotope Geochemistry, Guangzhouz Institute of Geochemistry, Chinese Academy of Sciences DS‐TIMS 0.94 0.04

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