We have identified and quantified Zn species in the Japanese geochemical reference materials (JLk-1, JSO-1, JSd-1-4, and JMs-1-2) by combining the sequential extraction procedure developed by the Community Bureau of Reference (BCR) and X-ray absorption near edge structure (XANES) spectroscopy. XANES spectroscopy revealed that: 1) target phases predicted by the BCR protocol, such as Zn-bearing Fe hydroxides and organic matter, are less abundant in the reference materials; and 2) Zn adsorbed to the phyllosilicates and the weathered surfaces of mafic minerals was selectively extracted by the BCR protocol. The weathering products of sphalerite, authigenic ZnS precipitate, Zn-bearing Fe hydroxides were identified in stream sediments influenced by mining activity and contaminated sediments. Phyllosilicates were the dominant phases of Zn extracted by the BCR protocol, even in these materials. The Zn²⁺ ion is hydrolytically-stable and easily dissolves in water. The speciation study revealed that Zn in nature would be selectively adsorbed by phyllosilicates, because their surfaces are charged negatively around neutral pH, and strongly bind Zn. The BCR extraction protocol does not provide the predicted results for Zn speciation, but is still helpful to the stability assessment, because Zn extracted at early-stages of extraction is interpreted to be a labile fraction that is easily-released to the environment.

An integrated analysis of the heat production of sedimentary rocks from the Sichuan Basin was carried out by measuring the radioactive heat-producing elements (HPE) (U, Th, and K) in well samples. The mean heat production was calculated to be 0.83 ± 0.36, 1.09 ± 0.38, and 1.07 ± 0.39μ, 0.40 ± 0.39, and 0.35 ± 0.27 μW/m³ in sandstone, siltstone, mudstone, limestone and dolomite, respectively. In terrigenous sedimentary rocks, the contributions of U, Th, and K to the heat production were 65–68%, 26–28%, and 6–8%, respectively. The mean heat production of sedimentary layer in the Sichuan basin was estimated as 0.77–0.78 μW/m³, the gross heat production of sedimentary layer was calculated to be 8.11 mW/m² in the west, 5.28 mW/m² in the center and 7.78 mW/m² in the east. The heat production of sedimentary layer contributes ~15% to the surface heat flow in the western and eastern Sichuan basin, and ~8% in the central basin. This study classified the lithology based on their contributions of radioactive elements to the heat production, which provides an insight to the differentiated heat productions of the sedimentary layers in the Sichuan Basin.

Ion-adsorption type rare earth elements (REE) deposit in weathered granite is the main source of REE essential for high-technology industries. However, this type deposit has not been well surveyed in Japan. In this study, Bulk REE abundances (=REE_TOT), ion-exchangeable REE (=REE_EX) by ammonium chloride solution, and percentage of REE_EX relative to REE_TOT (=REE_PER) in fresh and weathered granite samples in Southwest Japan (i.e., Hiroshima and Shimane Prefectures) were determined. The REE_TOT and REE_PER were comparable to those of ion-adsorption type REE deposits in China. This finding indicates that ion-adsorption type REE deposits can also be found in Japan. Furthermore, extended X-ray adsorption fine structure (EXAFS) spectra of yttrium in original samples and samples after the extraction of ion-exchangeable REE showed that (i) REE in samples with high REE_PER mainly forms outer-sphere (OS) complexes and (ii) the remaining REE in the rocks after the extraction forms inter-sphere complexes. These findings suggest that ion-exchangeable REE forms OS complexes, which causes the high extraction rate by the ion-exchange reaction.

In the present study, a novel and simple method to measure picomolar to subpicomolar dissolved Zr, Hf, Nb and Ta in seawater is described. The method provides a preconcentration step (250 times) by mini-column filled with a commercially available chelating resin. The proposed method has a lower blank and better precision than previous methods. Furthermore, using a more dilute hydrofluoric acid as eluent, the new method quantitatively recovered (97–102%) all of these elements spiked in seawater. Determination of Zr, Hf, Nb and Ta in North Pacific seawater at 100 m depth were 39, 0.14, 2.4 and 0.03 pmol/kg, respectively. These results are consistent with previous reports. Finally, we applied the proposed method to seawater samples taken from the North Atlantic Ocean during the U.S. GEOTRACES expedition and report the results for the first time in this paper.

Detrital zircon U-Pb dating is a powerful tool to trace sources for sedimentary basin and to understand of geological history in structurally complex areas. This study established an analytical protocol for measurement of detrital zircon U-Pb age by LA-MC-ICP-MS. Because detrital zircons normally have a large Pb content variation (several ppm to hundred ppm), which leads to large variations for Pb signal intensity, two sets of detector arrays were used. For Pb-rich zircons, ²⁰⁶Pb was collected with Faraday cup detector array, while for Pb-poor zircons, ²⁰⁶Pb was collected with ion counter detector array. The results of ²⁰⁶Pb/²³⁸U age and ²⁰⁷Pb/²³⁵U age for six well-known and widely used zircon standards agree within 0.5% and 1% respectively of the preferred values measured by ID-TIMS. The precision of ²⁰⁶Pb/²³⁸U age and ²⁰⁷Pb/²³⁵U age of the six zircons vary from 0.6% to 2.3% and 0.9% to 2.3% (2SD), respectively.