Chemical characteristics of sedimentary rocks and meta-sedimentary rocks of tectonic belts in Japanese Islands and geological environments of their formations

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We have installed an ICP-AES spectrometer (Seiko SPS-1500R) and established REE plus Y determinations in various types of sedimentary rocks. We have applied our ICP-AES method to determining REE and Y in limestones, dolostones, metamorphic rocks, Precambrian iron ores, and deep-sea ferromanganese nodules. We focused on the chemical classification of carbonate rocks in the tectonic belts in Japanese Islands from REE and Y analyzes. The three types of (1) coral reef-type, (2) continental margin-type, and (3) deep-see type are distinguished. Their geological environments of carbonate rock formations inferred from our geochemical data are in good agreements with previous sedimentological and geological analyzes.We also made an important theoretical study of "Tetrad effect", which must be an important basis to understand REE behaviors in sediment-water systems in low temperatures. From this viewpoint, experimental study on partitioning of REE and Y in the system of FE-Mn hydroxide and NaCl solution have been initiated. It is the first step to elucidate the REE behaviors not only in sedimentary rock formations but also in aquatic earth's environments.