In 2025, a new ocean science drilling program (IODP3) will begin. As core members, Europe and Japan provide drilling platforms, and a transparent, flexible, and international organization is being established to make the program available to researchers around the world. The IODP3 will be a collaborative effort among researchers in the fields of Climate, Deep Life, Geohazards, and Deep Earth to develop an unprecedented and feasible drilling program. This presentation will introduce the results of seismogenic zone drilling and the future structure of the project, which will help lead to the submission of drilling proposals and legacy core data analysis proposals.

MORs, hotspots, and petit-spot magmas on present Pacific plate record geology and geochemistry of crust and mantle since 180 Ma. This study presents submarine geology, oceanic crust, suboceanic mantle on the NW Pacific plates prior to subduction, where the submarine environment, lithosphere, and underlying asthenosphere could be modified more extensively just prior to subduction.

In the northwestern part of the oceanic Pacific plate off northeast Japan, JAMSTEC has conducted extensive controlled-source seismic surveys. The results of the structural analysis show that there is a good correlation between the thickness of the oceanic crust and the water depth there, suggesting the static isostacy. This means that a few hundred meters difference in water depth corresponds to a few tens of percent difference in the thickness of the oceanic crust, resulting from the formation process of the oceanic plate at the ancient spreading ridge axis. A petit-spot site was found in an area of thin crust, suggesting that the ancient scars caused at the spreading ridge axis may control current volcanic activity on the old oceanic plate.

Petit-spot volcanism provide information on the asthenosphere beneath an old plate. Here, this study reports the volatile, major, and trace element compositions of quenched glass of petit-spot basalts and identify the chemical composition of upper mantle beneath the NW Pacific plate, where some enriched materials are recognized in spite of asthenosphere.

The use of various plastic materials in agricultural production has been used to produce high-quality crops, save labor in agricultural work, and reduce environmental impact. On the other hand, the recent plastic waste problem has triggered a need to address new issues, such as proper disposal of plastic materials used in agricultural fields and prevention of runoff. In addition, microplastics (small pieces of plastic smaller than 5 mm) mixed in soil are attracting attention internationally as an emerging risk, and their effects on soil ecosystems and agricultural crops are being actively studied. This presentation will focus on primary microplastics derived from coated fertilizers used in agricultural fields and report the results of monitoring the transfer process from agricultural fields to the ocean.

Along with carbon neutrality, interest in circular economies is growing. The essence of the circular economy is the economic implementation of "resource efficiency improvement, which achieves functional enhancements such as longer life, miniaturization, intensification, higher functionality, and multifunctionality, while conserving resources and energy. To achieve this, impurity control is necessary to create high-purity materials, regardless of primary or secondary resources, and separation engineering research is being conducted for this purpose. To achieve highly efficient separation, it is necessary to control various reactions, including the sorption of trace elements at the solid-gas-liquid interface, such as reaction rate control under various external forces that cause changes in heat and pressure. Although the time scales are generally very different, such separation phenomena can be regarded as accelerated processes of various reactions that are well understood in geochemistry. It is expected that the knowledge gained from geochemistry will lead to the creation of innovative separation technology processes.

Seawater is expected to be directly used as a process water for the copper ores flotation plants, where pyrite is depressed under alkaline condition (>10). However, excess alkaline agents could be consumed due to the buffering effect of seawater salts, and introducing seawater to the plant causes the generation of hydrophilic particles under the pH condition, resulting in a decrease in the recovery of valuable minerals. This study investigated the potential effect of hydrophilization on pyrite and chalcopyrite surface by promoting oxidative dissolution and bacterial adhesion using two strains of marine iron-oxidizing bacteria (Thalassospira sp., Mariprofundus sp.). We observed selective adhesion of hydrophilic bacterial cell on pyrite surface but little difference in the chemical properties on the pyrite surface by bacterial reaction. Therefore, the hydrophilic/hydrophobic property of marine iron-oxidizing bacterial cell is a significant controlling factor of flotation behavior in seawater.

Although releases of Japanese eel have been conducted to maintain and increase stock levels, the effects on stock maintenance are unknown. Furthermore, there is a risk of disturbing the original distribution of natural individuals or making the proportion of natural and cultured individuals unknown. In addition, existing methods for discriminating between natural and cultured fish lack accuracy and simplicity. Therefore, we aimed to develop a method to discriminate between wild and farmed individuals by analyzing stable isotopes of carbon and nitrogen in the eye lens. Since the lens is formed in chronological order from the inside out, the composition of the eye lens can be compared during the period when there is a difference in food intake to discriminate between wild and farmed individuals. The carbon and nitrogen isotopic compositions of the eye lens were analyzed using samples of farmed individuals before release and wild individuals from rivers without release. The results showed that the distribution of carbon and nitrogen isotope ratios were distinctly different between wild and farmed specimens, suggesting that it is possible to discriminate between wild and farmed specimens. This method can be applied to estimate the contribution of farmed individuals to spawning, the original distribution area of wild individuals, and the ratio of wild and farmed individuals in each river.

In recent years, Japan has been planning to construct deep-sea infrastructures for the mining of seabed mineral resources and effective utilization of the vast exclusive economic zones. The use of cement-based materials such as concrete is essential for the construction of deep-sea infrastructures, however exposing them to deep-sea environments deteriorates faster than that of terrestrial environments. Therefore, there is a strongly need for detailed evaluation of the effects of deep-sea environments on cement-based materials and development of them so that can maintain durability in such environments for a long time. In this study, we focused on biofilms formed by marine bacteria, which have high alkali tolerance and can grow on cement surfaces, and investigated their effects on the durability of cement-based materials. The results showed that the formation of biofilms on the surface of materials inhibits the penetration of chloride ion concentration, suggesting the possibility of improving the durability of cement-based materials.

In this presentation, I will discuss the three basic elements of geochemistry - partitioning, diffusion and dating - from the perspective of demonstrating phenomena that occur in nature. In order to analyze a sample correctly using partitioning, diffusion and dating, it is necessary to determine the system of the chemical reactions, and characterize the phases that appear and the relationships between them. Then we can select the chemistry to be applied to the system. For this selection of the chemistry to be applied, an understanding of the quantitative accuracy of the three basic elements of geochemistry is necessary. For characterization, it is important to limit the chemical analysis capabilities required for the analysis.