Al-rich chondrules (ARCs) have characteristics of both Mg-rich chondrules and CAIs, and are important materials for elucidating the relationship between chondrules and CAIs. However, since ARCs are a rare constituent of meteorites, there are very few examples of Cr-Ti isotope ratio measurements in previous studies. In this study, we measured the Cr-Ti isotopic ratios of a total of five ARCs found in two types of CV chondrites. The Ti isotopic ratios of ARCs were found to vary significantly and showed large isotopic anomalies, while the Cr isotopic ratios did not show significant anomalies. The influence of CAI mixing on the isotopic composition of ARCs was found to be significant only for Ti, suggesting that materials with Cr-poor compositions of CAIs and materials with NC-like isotopic compositions are related to the formation of ARCs.

Ice mantles of interstellar dust particles in molecular clouds are one of the most suitable sites for prebiotic molecular formation. Organic compounds including amino acid precursors are thought to have been produced by galactic cosmic ray irradiation in the ice mantle of interstellar dust particles in molecular clouds. Previous studies have shown that macromolecular amino acid precursors (CAW) are produced from carbon monoxide, ammonia, and water abiotically in experiments simulating molecular cloud environments. It was possible that the amino acid precursors produced in interstellar molecular clouds were incorporated into the primitive small bodies during the solar system formation, and were affected by gamma-rays and heat from the radioactive decay of ²⁶Al. Considering these factors, experiments were conducted to investigate the stability of amino acids and macromolecular amino acid precursors against gamma-rays in the interior of small bodies. Amino acids (glycine, alanine, valine, Isovaline, alpha-aminobutyric acid, alpha-aminoisobutyric acid) or CAW was dissolved in ammonia aqueous solution or in an aqueous solution of formaldehyde and ammonia. These solutions were irradiated with gamma-rays from ⁶⁰Co source. The results showed that the macromolecular amino acid precursors (CAW) were more stable than free amino acids against gamma-ray irradiations. Moreover, we confirmed that amino acid precursors could be newly synthesized by gamma-ray irradiation.

Aqueous alteration in meteorite parent bodies would provide a suitable site for the formation of sugars in the prebiotic environment. In meteorite parent bodies, formose-type reactions are expected to occur, in which various organic substances including sugars are produced. The progression of this reaction depends on various factors.In this study, we focused on the effect of minerals on the formose-type reaction and conducted experiments in vitro. The experiments were conducted by preparing samples in glass tubes, derivatizing it, and analyzing it by GC/MS. In this study, the sugars analyzed were aldoses with carbon numbers ranging from 4 to 6.The experimental results showed that the aldose formation reaction proceeded faster when olivine was present in the system. This suggests that olivine has a catalytic effect on formose-type reaction, which may be due to multiple factors such as the surface structure of olivine and its metamorphic effect. In order to investigate this catalytic ability in more detail, the effects of other minerals, such as serpentine, on the formose-type reaction were also investigated.

Within the parent body of the asteroid Ryugu, it is estimated that heating caused the melting of water ice, which then reacted with reducing materials to create an alkaline and reductive aqueous environment. Abiotically synthesized organic matter can be the origin of the organic matter on Earth. To estimate the water environment during aqueous alteration in parent body of Ryugu, we measured the X-ray Absorption Near Edge Structure (XANES) of chromium (Cr), titanium (Ti), vanadium (V), arsenic (As), iron (Fe), and sulfur (S) in samples from Ryugu and the CI chondrite Orgueil meteorite. We compared these results with thermodynamically calculated Eh-pH diagrams. In addition, we examined valence changes of these elements due to atmospheric oxidation by comparing them with the Orgueil meteorite results. The findings indicated that Cr was predominantly in the Cr(III) state across the Ryugu samples, with some Cr(II) also observed. Ti was mainly present as Ti(IV), distributed between ilmenite and phyllosilicates. As was primarily in the As(V) state in phyllosilicates and in more reduced species in phosphate-rich areas. V was uniformly distributed as V(III) regardless of mineral structure. These valence states suggest that Ryugu's parent body may have experienced a highly reducing environment where water decomposed to produce hydrogen.

Al-Ti-rich diopside (fassaite) in Ca-Al-rich Inclusion (CAI) can be expected to reflect the environmental change in the protoplanetary disk. Rare Earth Elements (REE)would be used as a redox indicator. However, it has not been reported the signatures of REE during fassaite crystal growth. In this study, we carried out the REE analysis by LA-ICP-MS considering the fassaite crystal growth using Ti contents by EPMA analysis. REE pattern and Sc/Lu ratio show the trend of fractional crystallization from the CAI melt. Y/Ho and Tm/Tm* suggested that this CAI precursor may not be a condensate from fractional gas. On the other hand, although Ce/Ce* and Yb/Yb* cannot be used as redox indicators, Eu/Eu* has a negative correlation with TiO₂ content, suggesting that Eu/Eu* may be used as a redox indicator of CAI melt during fassaite crystal growth.

In the protoplanetary disks, different organic matters can be generated via various chemical processes, including photohcemical reactions on the disk surface and hydrothermal reactions in the parent body of asteroids. These organic materials may play a pivotal role for promoting the collisional growth of dust in the disk due to their high stickiness. In this study, several organic analog materials were produced by simulating different chemical processes in the disks. Their chemical structures were investigated via mass spectroscopy, infrared/visible/ultraviolet spectroscopy, raman spectroscopy, and elemental analysis. The surface energy and elasticity, which control the sticking properties of these organic analog materials, were determined by using atomic force microscope and analysis of IXS spectra, respectively. Based on the results of the chemical analysis and the measurement of the physical properties, chemical structure and temperature dependence of these physico-chemical properties were revealed. Our results suggest that the organic materials with a variety of functional groups show higher surface energy and lower elasticity compared with aromatic-rich organic materials. The temperature dependence of the surface energy and elasticity followed the Arrhenius equation, with indicating that the surface energy decreases and the elasticity increases at lower temperatures. Our results also suggest that the sticking properties of organic materials increase at higher temperatures, although the dependence of chemical structure is under debate. Our results imply that organic matter may have promoted collisional growth of dusts in high-temperature regions inside the H2O snow line in the protoplanetary disks.

Goethite, a common iron oxide formed by water reaction, is rarely found on the Martian surface. Under low temperature conditions, crystalline iron oxides are formed by the transformation of ferrihydrite, and it is known that water conditions such as pH and salinity affect the transformation of ferrihydrite. In this study, we systematically investigated the transformation behavior of ferrihydrite under a comprehensive range of water conditions, including a water chemistry of early Mars. Then, we attempted to give an indication of the rarity of goethite on Mars.

Sea spray aerosols (SSA) are generated when sea spray is released into the atmosphere through the bursting of bubbles caused by strong winds and breaking waves. Conventionally, SSA has been considered to consist mainly of inorganic salts derived from seawater, such as NaCl and MgCl₂. However, recent studies have highlighted that the sea-surface microlayer (SML), which includes marine microorganisms and their exudates, plays a crucial role in the formation of SSA enriched in organic matter, thus significantly altering the morphology and composition of SSA. The physical properties and the proportion of diverse organic substances derived from SML present in individual particles may result in atmospheric behavior that is markedly different from SSA composed solely of inorganic salts. In this presentation, we focus on the mixing state at the individual particle level and introduce several case studies evaluating the impact of organic matter on the physical properties of SSA.

Subducted sediment derived components alter the chemical composition of the mantle and can influence magmatism in overlaying volcanoes. Stable Mg isotopic analysis is a newly developed tool which is frequently used to detect the type and chemical characteristics of the subducted sediments. Mg isotopes fractionate during silicate weathering and carbonate precipitation and marine carbonate sediments show some of the lowest Mg isotopic ratios on Earth. Although Mg isotopic analysis of Cenozoic volcanic rocks from northeast China have indicated involvement of carbonate sediments in the mantle below East Asia, no such data is available for the volcanoes in Japan showing similar chemical signatures. In this work we attempt to decipher the Mg isotopic signatures from the mantle below the southwest Japan arc.

Subduction zones play an important role not only in surface volcanism and seismic activity but also in material cycling from the Earth's surface to mantle [e.g., 1]. In recent years, Molybdenum (Mo) isotopic compositions have been used to trace the origin of slab-derived fluids in subduction zones and the recycled oceanic crust [e.g., 2]. Mo isotopic compositions have also been studied in volcanic rocks from several oceanic arcs and oceanic island basalts (OIB), but the mechanism of recycle processes of subducted oceanic crust are still unclear [e.g., 2-4]. Oki-Dogo Island is an island in the Japan Sea, situated on the rear arc side of southwestern Japan, where a variety of alkali volcanic rocks from the Miocene to Quaternary period have been reported [e.g., 5]. In this study, we attempted to estimate the recycled slab material into the source magma in alkali volcanic rocks after Oki-Dogo Island by determining the Mo isotopic compositions of alkali basalts using the double-spike technique with TIMS.Mo isotopic compositions of Oki-Dogo Island basalts show relatively lower values (-0.30 to -0.11, N=4) than the estimated depleted mantle [6]. This is also similar to the range of Mo isotopic compositions in the OIB and Mariana Trough in previous studies [4,7]. Previous studies have suggested that such Mo isotopic compositions, which are lower than the estimated DM value, together with less radiogenic Pb isotopic composition and Ce/Mo ratios in volcanic rocks, can be explained by the effect of recycled oceanic crust [3,4]. Oki-Dogo Island basalts also show less radiogenic Pb isotopic compositions and low Ce/Mo ratios, similar to or lower than those in previous studies, indicating that they may have received contributions from the recycled component. In addition, the Mo isotopic compositions of the Oki-Dogo Island basalts shows no clear correlation with Mo concentration but a negative correlation with the La/Yb ratio, suggesting that the Mo isotopic composition may have changed with magmatic differentiation within the basalts. Therefore, it is necessary to investigate this issue in more detail in the future.References [1] Spandler and Perard, 2013, Lithos., [2] Freymuth et al., 2015, EPSL, [3] Cai et al., 2024, Chem. Geol., [4] Willbold and Elliott, 2023, EPSL, [5] Uchimizu, 1966, J. Fac. Sci. Univ. Tokyo, [6] Uto et al., 1994, GJ, [7] Kobayashi et al., 2002, GKK, [8] McCoy-West et al., 2019, Nat. Geosci., [9] Li et al., 2021a, Geol.

In March 2024, we determined the water vapor isotopic composition of the plumes emitted from three different fumaroles (H, Y2, Y3) within the same fumarolic field at Kirishima Iwo-yama using the method described in Takahashi et al. (2019). We also analyzed isotopic composition of the fumarolic vapor condensed water samples collected by the cold trap. As a result, the three plumes exhibited different water vapor isotopic compositions from each other, and these were plotted on the isotopic fractionation line assuming Rayleigh fractionation at the observed temperature. The isotopic composition extrapolated on the meteoric water - magmatic water mixing line was consistent with the estimated value for magmatic water and was generally consistent with the isotopic composition of the condensed water samples. Therefore, it is highly likely that some of the water vapor released from the fumaroles quickly condenses and is removed from the plume.

At Kirishima Iwoyama volcano, an eruption occurred on April 19, 2018. In this study, continuous observations of fumarolic gas composition using Multi-GAS were conducted in the vicinity of fumarole H from July 2017 to January 2020 to monitor volcanic activity at the volcano. The results of the continuous observation showed that the SO₂/H₂S ratio and the daily maximum values of SO₂ concentration had decreased since the observation started but turned to an increasing trend in January 2018 and showed a remarkable increase of about 100 times from February to March 2018. On the other hand, the CO₂/H₂S ratio showed an increase or decrease corresponding to the change in the SO₂/H₂S ratio during the same period, but the range of the change was smaller than that of the SO₂/H₂S ratio. After the eruption, the SO₂/H₂S ratio remained lower than before the eruption, but showed a sharp increase in June 2019 and then decreased again. Magmatic gases of deep origin are supposed to be supplied to the shallow hydrothermal system, and the observed variations in fumarolic gas compositions can be explained by reactions of sulfur precipitation and sulfur dioxide disproportionation.

Submarine mud volcanoes, which are releasing fluids originated in deep subsurface. Around Japan, they are found extensively in the Kumano Basin off the Kii Peninsula and off Tanegashima Island. Recent detailed topographic surveys have also identified submarine mud volcanoes distributed in areas Hyuga-nada and off Kikaijima Island. During the KH-23-4 cruise of R/V "Hakuho-Maru" in August 2023, sediments core samples were collected from these mud volcanoes. We investigated the origin of the fluids in these mud volcanoes using porewater chemistry, including Cl^-, Li, and Na concentrations as well as stable isotopic compositions of hydrogen and oxygen in the porewater. The Cl^- concentrations decreased with depth in all mud volcanoes. Specifically, the Cl^- concentrations in a mud volcano off Kikaijima were 70% lower than those of seawater. This decrease suggests that the low Cl^- fluids migrate from deeper depths to the seafloor surface. The stable isotopic compositions of hydrogen and oxygen decreased and increased, respectively, with decreasing Cl^- concentrations at all active mud volcanoes, indicating a characteristic of water derived from clay mineral dehydration. The Li concentrations increased with depth, especially in mud volcanoes with low Cl^- concentrations. The experienced temperatures of fluid estimated using the Na/Li geothermometer were approximately 140 degrees Celsius for all mud volcanoes, suggesting that the fluids derived from the clay mineral dehydration is supplied from several kilometers below seafloor.

In an attempt to understand the late accretionary history of Earth, we investigated Archean rocks from Acasta complex. The Acasta Gneiss complex hosts the oldest rocks preserved on Earth with a crystallization age of 4.03 Ga (1). Molybdenum isotopes provide important insights into the late accretionary history of our planet. Due to its moderately siderophile character, Mo partitioned largely into the core and the present day bulk silicate Earth Mo isotope composition is an integration of the original and late accreted material (2). Mass independent (nucleosynthetic) Mo isotope anomalies are a valuable tool in constraining genetic relationship among meteorites and planetary materials. However, a recent study reported the spurious Mo mass independent anomalies resulting from a mass dependent fractionation of Mo isotopes in terrestrial samples (3). We have conducted a Mo isotopic investigation (mass independent and mass dependent) of several mafic and intermediate rocks from the Acasta Complex, that have been least affected by later events involving widespread migration of fluid mobile elements (4). References (1) Reimink et al. (2019) Earth s Oldest Rocks. (2) Dauphas (2017) Nature 541,. (3) Budde et al. (2023) Geochemistry, 83. (4) Koshida et al. (2016) Precambrian Res. 283.

To characterize the volatile components of the Icelandic plume, we collected picritic basalt from spatter, scoria, and subglacial pillow lava from a wide area of Iceland, and measured the volatile content and hydrogen isotope ratios of volcanic glass and melt inclusions in olivine. A negative correlation between water content and hydrogen isotope ratios is observed, suggesting that this correlation involved a mantle with lower water content and a higher D/H ratio than the upper mantle (dD ~ -40 per mill) and a mantle rich in water and with a lower D/H ratio than the upper mantle. Both mantle components may have a deep Earth origin, but further analytical analysis is required to clarify this.

In this study, we estimate the recycling age of the oceanic crust by combining the Nd model age and the Pb-Pb model age of the OIB classified as FOZO and HIMU. The important factor in this method is 207Pb/206Pb, but this isotope ratio changes depending on the correction method for the mass fractionation effect during measurement. Since the 207Pb/206Pb reported so far uses different methods and standard values, it is not possible to estimate the correct recycling age without evaluating the impact of the correction for the mass fractionation effect. In this presentation, we unify the mass fractionation effect correction method and report the recycling age estimated by the isotope ratio.

Understanding of the fluid-rock interaction in fault gouges is important to evaluate the activity of faults and reactivation of the inactive faults. The fluid-rock interaction in Taiwan Chelungpu fault activated at the Chi-Chi earthquake has been discussed by Ishikawa et al. (2008) based on the elemental distribution in hydrothermal experiments with sediments and trace elements concentrations and isotope ratios of the fault gouges. In this study, we tried to evaluate the fluid-rock interaction in the Gosukebashi Fault of Rokko Granite based on geochemical compositions of the fault gouge in the similar approach with the above. The analyses of chemical compositions and Sr isotopes of the Gosukebashi Fault samples indicated that the fluid-rock interaction in the Gosukebashi Fault was different from that at 350 degree C seen in Chelungpu fault and the gouge in this study did not interact with hot fluid during past faulting movements. We will carry more detailed chemical composition and isotope analysis to reveal the changes in chemical composition of the gouge caused by fault movement and understand the fluid-rock interaction of the Gosukebashi Fault gouge.

The earthquake swarm at the northeastern Noto Peninsula, including the 2024 Noto Earthquake, has continued for a long duration. In order to elucidate geochemical cycles beneath the northeastern Noto Peninsula during the earthquake swarm period, temporal variations of spring chemical and isotopic compositions were investigated in this study. Temporal variations of obtained geochemical data such as 3He/4He ratios may reflect changes of permeability of aquifer rocks associated with seismic activity, or changes of contributions from the deep fluid with mantle-derived components due to the behavior of the deep fluid.

This study uses a combination of field observations coupled with in-situ CO2 flux measurements and helium and carbon isotopic data, to demonstrate the controls on CO2 origins and fluxes in a 400-km-long rift transecting northern Himalaya and southern Tibet. The findings in this study reveal that geophysical and geo-tectonic responses to continental underthrusting could facilitate massive crustal carbon mobilization and emission, making active collisional orogens globally important carbon sources.