The concentration of rare earth elements (REEs) in geological materials including SLRS-6 (natural water certified reference material) and JB1b, JA1, and JG2 (Standard Rock Materials of Geological Survey of Japan) can be used as a tracer to characterize various geochemical processes in earth systems. Particularly, accurate and precise determination of rare earth element concentration in natural waters is difficult due to their extremely low concentration and the interference of polyatomic oxides. In this study, we developed a method for accurate and precise determination of the REE (particularly heavy rare earth elements) concentrations in geological materials including natural waters using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) and group separation by 2-hydroxyisobutyric acid (HIBA). The REEs were separated into light rare earth elements (LREEs, La–Ce–Pr–Nd), middle rare earth elements (MREEs, Sm–Eu–Gd–Tb), and heavy rare earth elements (HREEs, Dy–Ho–Er–Tm–Yb–Lu) by a cation-exchange column (AG50W-X8 200–400 mesh) using HIBA. The recovery rates of each REE in the natural water sample exceeded 98%, whereas the recovery rates of each REE in rock materials exceeded 95% except for HREEs. The method developed in this study can accurately measure the REE concentrations (particularly HREE) in geological materials without polyatomic oxide interference during the REE analysis by using the MC-ICP-MS and, thus, can correctly interpret the geochemical implications of REEs in geological systems. The determination of the Sr concentrations and Sr isotopic ratios of SLRS-6 CRM and JB1b, JA1, and JG2 SRMs is also reported, and they are shown to be in good agreement with the recommended values.

The Pirrit Hills are located in the Ellsworth–Whitmore Mountains of West Antarctica. The Pirrit Hills granite exhibits significant negative Eu anomalies (Eu/Eu* = 0.01~0.25) and a REE tetrad effect indicating intensive magmatic differentiation. Whole-rock Rb-Sr and Sm-Nd geochronologic analysis of the Pirrit Hills granite gave respective ages of 172.8 ± 2.4 Ma with initial ⁸⁷Sr/⁸⁶Sr = 0.7065 ± 0.0087 Ma and 169 ± 12 Ma with initial ¹⁴⁴Nd/¹⁴³Nd = 0.512207 ± 0.000017. The isotopic ratio data indicate that the Pirrit Hills granite formed by the remelting of Mesoproterozoic mantle-derived crustal materials. Both chondrite-normalized REE patterns and Sr-Nd isotopic data indicate that the Pirrit Hills granite has geochemical features of chondrite-normalized REE patterns indicating that REE tetrad effects and negative Eu anomalies in the highly fractionated granites were produced from magmatic differentiation under the magmatic-hydrothermal transition system.

Two kinds of bottled mineral water from wells located in the northern (Baeksansu, BSS) and southern (Baekdusansu, BDS) areas near Mt. Baekdu (Changbai) were collected in order to monitor the chemical compositions of the groundwater near a potential volcanic area. The bottled water was produced between August 2014 and June 2017, and corresponds to the Na-HCO₃ water type. The trend in variation of each chemical component between the two bottled waters was different. The BDS bottled water from the southern area of Mt. Baekdu showed a dramatic change in chemical composition during the study period, whereas the BSS bottled water from the northern area did not show any significant change in chemical composition. In particular, the BDS bottled water showed either systematic increases or decreases of chemical components relative to the Cl concentrations. However, the BSS bottled water did not show such trends. It was confirmed that the chemical composition in the groundwater was constant, even though the monitoring period lasted for about two years. Our data indicate that it may be possible to use the chemical composition of the bottle water produced from the groundwater in the volcanic area as a proxy for monitoring the geochemical environmental change of the groundwater aquifer.