In this study, the equilibrium isotope fractionation factors between Cd-bearing aqueous solutions and minerals were predicted. The theoretical method used to calculate the Cd isotope fractionation factors is the first-principle quantum chemistry method (Cd: LANL2DZ, other atoms: 6-311 + G(d, P)). Reduced partition function ratios (RPFRs) of Cd-bearing minerals (Greenockite and Sphalerite) were modeled by the method of the volume variable cluster model (VVCM). The theoretical method of “water-droplet method” is used to simulate the solvation effect of different Cd-bearing aqueous solutions. The results show that, in most cases, the Cd-bearing aqueous solutions are enriched in ¹¹⁴Cd relative to Greenockite. The Cd isotope fractionation factors between Cd-bearing aqueous solutions and Greenockite are in the range of 0.433–0.083 (100°C). And the Cd isotope fractionations between different Cd-bearing species are believed to be widespread. Cd isotope fractionation factors between different reservoirs are of great theoretical significance to many geochemical processes such as surficial geochemical process and ore-forming process. These theoretical parameters are studied systematically and carefully in this study.

The Hayabusa2 spacecraft explored C-type near-Earth asteroid (162173) Ryugu and returned asteroidal materials, collected during two touchdown operations, to the Earth as the first sample from carbonaceous-type asteroid. The sample container, in which ~5 g of Ryugu sample was enclosed, was safely opened in the clean chamber system with no severe exposure to the terrestrial atmosphere. In the course of preparation operation of the sample container, two dark-colored millimeter- to sub-millimeter-sized particles were found outside the sealing part of the sample container. Because they look similar to the Ryugu particles inside the sample container, the particles were named as Q particles (Q from questionable). In this study, we investigated Q particles (Q001 and Q002) mineralogically and petrographically to compare them with potential contaminants (the ablator material of the reentry capsule and fine sand particles at the capsule landing site), Ryugu sample, and CI chondrites. The Q particles show close resemblance to Ryugu sample and CI chondrites, but have no evidence of terrestrial weathering that CI chondrites experienced. We therefore conclude that the Q particles are originated from Ryugu and were expelled from the sample catcher (sample storage canister) in space prior to the enclosure operation of the sample catcher in the sample container. The most likely scenario is that the Q particles escaped from the sample catcher during the retrieval of the sample collection reflector, which was the necessary operation for the sample container closing.

Analyses of elemental abundances by secondary ion mass spectrometry (SIMS) require matrix-matched standard samples to account for the matrix effect on correction factors. This requirement makes it difficult to obtain accurate results for geological samples of variable chemistry. In this study, we prepared 39 volcanic glasses of foiditic, basaltic, basaltic andesitic, rhyolitic and pure SiO₂ compositions, including synthetic samples and natural samples collected from the deep seafloor. The measured H₂O contents of these samples were in the range 0.02–4.8 wt%. We showed that calibration curves (H₂O content vs. ¹⁶OH^–/³⁰Si^–_SIMS ratio) differed according to the composition of the volcanic glasses. Our results demonstrated that for a particular ¹⁶OH/³⁰Si_SIMS ratio, water content could differ by up to a factor of five, depending on the composition of the volcanic glass. Although the correction factor (the slope of the calibration curve for water [H₂O/(¹⁶OH^–/³⁰Si^–)_SIMS]) was weakly correlated with SiO₂ content, we identified a stronger correlation with the molar weight (g mol^–1, on a one-oxygen mole basis) of the silicate glasses. Our results suggest that modification of the correction factor for the matrix effect on SIMS-based H₂O content of volcanic glasses according to their molar weights provides more accurate water contents of silicate glasses, regardless of their chemical composition and water content and without the need for a series of standard glasses of known water contents.

The whole-rock trace-element compositions of igneous rocks provide primary geochemical information about their petrogenesis. Such compositions can be determined by LA–ICP–MS analysis of fused-glass samples as well as the conventional solution ICP–MS method. However, in contrast to basalt and andesite, the fused-glass method is not suitable for Si-rich rocks (granite and rhyolite) due to the difficulty of making homogeneous glasses. To extend the method to Si-rich rocks, we adopted an MgO dilution process to prepare fused glasses and evaluated the technique by analysis of granite and rhyolite reference materials. Dilution of 30 mg of powdered samples with 10 mg MgO facilitated the preparation of homogeneous fused-glass samples of felsic rocks. LA–ICP–MS analyses indicate that the fused glass is homogeneous in the contents of most incompatible elements considered in igneous petrology. The glass enables the analysis of these elements in felsic rocks within 20% deviation from reference data. The sample data are consistent with reference values for rhyolite although Zr and Hf data deviate significantly (by ~40%) from reference values for granitic rocks.

To understand seawater properties, such as water mass structure and mixing, geochemical analyses are useful. However, geochemical datasets for seawater that fully cover coastal areas of Hokkaido, North Japan are lacking. Here we report comprehensive geochemical analyses of seawater (salinity, δ¹⁸O, δD, and Δ¹⁴C) collected in August–September 2021 from coastal areas of Hokkaido as well as the west coast of Tohoku (Northeast Japan). These datasets are expected to improve our understanding of seawater properties around Hokkaido, thereby contributing to oceanography, climatology, biogeochemical cycles, and fishery science.