In this paper, we report the analytical results of a new synthetic rhyolitic glass block fabricated from purified glass shards of Aso-4 tephra by using both solution and laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS). The Aso-4 b-W glass block is extremely homogeneous in 10 major and 32 trace elements with 1-standard deviation error (1SD), which is better than ~10% by LA-ICP-MS (n = 200). The Aso-4 b-W rhyolite glass was utilized to evaluate the matrix effect in LA-ICP-MS by using SRM 610 synthetic, GSE-1G basaltic andesite, and BHVO-2G basalt glasses as standards. The GSE-1G glass showed heterogeneity. Thus, the analytical results of Aso-4 b-W were normalized using BHVO-2G as the secondary standard. The major and trace element compositions were in good agreement within ~10% relative deviation (% RD) compared with those from electron probe micro analyzer and solution ICP-MS, respectively. However, the use of the SRM 610 standard showed a matrix bias of –24% RD in heavy rare earth elements, but these concentrations were in good agreement when renormalized to BHVO-2G. A matrix-matched glass standard is strongly recommended for precise analysis of rhyolitic glass. The Aso-4 b-W and the ATHO-G rhyolite glasses were analyzed using GSE-1G as the standard with BHVO-2G normalization. The results for both standard glasses were in good agreement with the reference values, thereby showing the importance of the matrix-matched standard. Moreover, this indicates that the new Aso-4 b-W glass block is suitable as a check standard in analyses of unknown rhyolitic glasses.

We examined quality of zircon U-Pb dating results by mean-of-ratios (MOR) reduction of time-resolved analysis acquired with quadrupole inductively coupled plasma mass spectrometer (ICPMS) and 213 nm YAG laser ablation system. Time-resolved MOR reduction has an advantage to enable statistic evaluation of stability of isotopic ratios and detect accidents in each measurement. We practically applied internal mean square weighted deviation (iMSWD) and correlation coefficient of linear regression to dating of five reference zircons. The MOR reduction provided reasonably accurate U-Pb ages with 2–3% errors of precision. However, their iMSWD suggested dispersion of isotopic ratios in excess of counting errors. The dispersion is inferably attributed to non-simultaneous measurements by quadrupole ICPMS, in addition to potential heterogeneity of samples. We also tested quality of age results from manually trimmed time profiles. The test suggested that ages from clipped profiles as short as 5 sec. are still useful if reduction of precision is acceptable. The method enables to extract meaningful ages from measurements containing accidents, when statistically stable parts out of accidents are properly clipped from the time profiles.

The short-lived radionuclide ¹⁰Be (t_1/2 = 1.4 Myr) present in the Early Solar System (ESS) provides important information about the astrophysical environment in which the solar system formed. However, the origin of ¹⁰Be in the ESS remains controversial. To reveal its origin, it is important to determine precise and accurate ¹⁰Be abundances in meteoritic components. The initial ¹⁰Be/⁹Be ratio can be estimated using ion microprobe analysis and a ¹⁰B/¹¹B-⁹Be/¹¹B correlation. The relative sensitivities for Be and B must be determined to obtain ⁹Be/¹¹B ratios of unknowns. Here, we report Be/B relative sensitivities for synthetic melilitic glasses and silica-rich NIST SRM 610 glass measured with a NanoSIMS ion microprobe. The Be/B relative sensitivities for melilitic glasses are identical to that of the NIST 610 glass within uncertainties, which suggests that the matrix effects, at least between the NIST 610 glass and melilite, are not significant with respect to Be-B measurements. The present results confirm that the observed variations in the ¹⁰Be/⁹Be ratios for CV calcium-aluminum-rich inclusions (CAIs) are real and the origin of ¹⁰Be must be attributed to irradiation by the active early sun. It is also inferred that the ¹⁰Be/⁹Be ratios of fractionation and unidentified nuclear effect (FUN) CV CAIs are not significantly lower than those for normal (non-FUN) CV CAIs, suggesting similar formation conditions.

Coral skeletons are robust tools for examining past environments. However, biogenic effects during skeletal formation cause uncertainties in paleoclimate reconstructions. Thus establishing a method to separate biogenic effects from abiogenic ones during skeletal formation is required. Here we utilized an open access and searchable gene database for the staghorn coral Acropora digitifera and examined the number of genes related to the elements in seawater to assess the origin of uncertainties in geochemical proxies. We found that A. digitifera has genes that can process at least 15 chemical elements as individual substances (Ca, Na, Zn, K, C, N, Cl, S, Fe, Mg, Mn, Cu, H, Mo, and Te) and transporters for seven of these elements (Ca, Na, Zn, K, Cl, Cu, and H). The number of Ca-related genes was the highest (at least 428 genes, including 53 transporters), whereas Sr, one of the most widely used geochemical proxies, was not found in the gene database. Furthermore, we analyzed skeletal samples of A. digitifera exhibiting different growth rates; their Sr/Ca ratios showed the lowest variation (1.9%), whereas other proxies (K/Ca, Na/Ca, and Mg/Ca) showed higher variation (2.3–11.9%). This might be linked to the number of genes related to the proxies (namely, the magnitude of biogenic and/or abiogenic effects). We suggest that considering elements with no relevant coral genes could provide effective criteria for reliable proxies (e.g., Sr/Ca, Li/Ca and U/Ca).

Isotopic fractionation of nitrogen associated with the trophic transfer of amino acids in food webs has recently been used as a powerful tool to estimate the accurate trophic levels of heterotrophic organisms. During the grazing process (i.e., trophic transfer), the amino acid, glutamic acid, is significantly enriched in ¹⁵N (by ~6–9‰) from diets to consumer heterotrophs; this is most likely caused by isotopic fractionation with the preferential deamination of ¹⁴N-amino group in glutamic acid during its metabolism. However, few studies determined the isotopic fractionation factor (α) of this process, which limits our understanding of the mechanism responsible for the isotopic fractionation and thus restricts its applicability in assessing the mass and energy transfers with respect to the amino acid assimilation/dissimilation cycle in the biosphere. In this study, we evaluate the α value associated with the enzymatic deamination of glutamic acid in vitro. Glutamic acid is gradually enriched in ¹⁵N by up to 4.0‰, when the deamination flux is increased up to 45.4%. The α value calculated is 0.9938 ± 0.0005 if the Rayleigh fractionation model is applied to the enrichment in ¹⁵N. Thus, we demonstrate the relationship between isotopic fractionation and deamination flux: for example, 8.0‰ fractionation corresponds to that 72 ± 3% of the diet-derived glutamic acid is deaminated in the consumer species at each shift of trophic levels in a food web.

To obtain accurate crystallization ages from Quaternary zircon, it is necessary to consider the contributions of common Pb and initial disequilibria caused by Th/U and Pa/U fractionation in the zircon-melt system. The disequilibrium in the melt also has influence on the resulting age. This study presents a method for calculating corrected U-Pb ages of Quaternary zircon. In the proposed method, initial disequilibria and common Pb are comprehensively accounted for by a single correction based on a modified Tera-Wasserburg concordia diagram (modified ²⁰⁷Pb method). A bisection method is used to quantitatively evaluate the influence of all factors employed in the correction on the resulting U-Pb age and its uncertainties. If the contribution of Pa/U partitioning is ignored (i.e., when using the conventional ²⁰⁷Pb method), the systematic age error for a 100 ka zircon is ~9.4%. Melt disequilibria on ²³⁰Th and ²³¹Pa also have significant influence on the calculated age, when it is non-negligible (e.g., basaltic rocks). Consequently, we suggest that the dating of very young zircon (<100 ka) with the ²⁰⁷Pb method requires precise estimation of both Th/U and Pa/U partitioning in the zircon-melt system.