Vol.9 No.2 2016

Research paper : Development and utilization of geochemical reference materials (T. OKAI)−66−Synthesiology - English edition Vol.9 No.2 (2016) including some for future research. Such an amount of rock could be secured with relative ease at the selected locations.As mentioned earlier, these two types of reference materials were highly praised and led to the creation of a project status for the work. Subsequently, representative rock types of Japan were prepared in the volcanic and sedimentary series, and for the very important granite (G), basalt (B), and andesite (A), three kinds of samples were prepared for each rock type, as shown in Table 1. Because each rock type is subdivided according to various characteristics even within the same general rock type, the whole geology was observed and reference materials were prepared from important sections. Using basalt as an example, the basalt produced in Japan can be divided roughly into three types according to the mineral and chemical compositions: alkaline basalt rich in sodium and potassium but poor in iron, tholeiitic basalt rich in calcium and iron but poor in sodium and calcium, and high-alumina basalt that falls between the previous two and is rich in aluminum. For each division, JB-1 (Sasebo, Nagasaki Prefecture), JB-2 (Izu Oshima Island), and JB-3 (Mount Fuji) were prepared, respectively.4.1.2 Sample selection suitable for instrumental analysis and environmental analysisOnce the volcanic and sedimentary series were completed in the 1980s, sample selection based on geological classification changed to selection based on analytical chemistry. Specifically, as appropriate concentration in samples was desired in order to prepare calibration curves for instrumental analysis, such as atomic absorption spectrometry and ICP atomic emission spectrometry, by ranking previously prepared samples in their order of concentration of each component, samples were selected to fill the gaps, and the instrumental analysis series was prepared. A specific example is JSy-1 (syenite), which is rich in aluminum, sodium, and potassium. As there was no appropriate sample in Japan, a reference material was prepared by purchasing a source rock from Canada.Around that time, environmental research became active globally, and the need to analyze environmental samples such as soils and sediments increased significantly. At laboratories that prepared geochemical reference materials, the “Geochemical Map” project—the mapping of elemental concentration—progressed simultaneously, and as reference materials for the river and marine sediments used to make geochemical maps were desired, preparation of the environmental analysis series began. A characteristic example is JCp-1 (coral). To reconstruct environmental information of the marine environment from the present to several hundreds of years ago, various elements in coral samples were analyzed at many laboratories. However, there was a problem in the reliability of the analytical results. Therefore, in response to requests from related projects, a coral reference material for general chemical analysis was prepared for the first time in the world.[11] It was used worldwide to improve analytical accuracy (improved reconstruction accuracy of environmental change) and for comparison of analytical results between laboratories (securing of reliability of analysis).4.2 Grinding of samplesJG-2 Granite, Naegi, Gifu PrefectureJG-1 Granodiorite, Sori, Gunma PrefectureJCp-1 Coral, Ishigaki Island, Okinawa PrefectureSample cross section (above)Blocks cut for grinding (bottom)JCh-1 Chert, Ashikaga, Tochigi PrefectureFig. 5 Examples of sampled source rocks and sampling sites


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