Razieh Chaharlang, Jalil Ghalamghash, Yu Saitoh, Mihai N. Ducea and Axel K. Schmitt : Sr Nd isotopes of Sabalan Volcano, NW Iran: insights into the origin of collisional adakites and geodynamic implications, International Journal of Earth Sciences, Vol.112, 2065-2080, 2023.
A. Tsuneki, N. Watanabe, Ryo Anma, S. Jammo, Yu Saitoh and S. Ahmad : Preliminary report of the Charmo (Jarmo) Prehistoric investigations, Al -Rafidan, Vol.44, 1-34, 2023.
3.
Etsuo Uchida, Shinya Nagano, Sota Niki, Kou Yonezu, Yu Saitoh and Ki-Cheol Shin : Geochemical and radiogenic isotopic signatures of granitic rocks in Chanthaburi and Chachoengsao provinces, southeastern Thailand: Implications for origin and evolution, Journal of Asian Earth Sciences: X, Vol.8, No.100111, 2022.
(要約)
The Chanthaburi, Pliew, Klathing, Khao Cha Mao, and Khao Hin Son granitic bodies in Chanthaburi and Chachoengsao provinces in southeastern Thailand, which are located on the southwestern side of the Mae Ping Fault and eastern side of the Klaeng Fault, were investigated. In this study, magnetic susceptibility measurements, whole-rock chemical composition and Nd-Sr isotope analyses, and zircon U-Pb dating were conducted on these granitic bodies. The surveyed granitic rocks are classified as I- to A-type granites, are of the ilmenite series, and show clearly negative Eu anomalies, which suggest they formed under reducing conditions. Nd-Sr isotope ratios indicate continental crust material involvement in the formation of these granite bodies. The magnetic and geochemical signatures are similar to those of granite bodies in southwestern Cambodia. The study area is thus considered an extensional area of southwestern Cambodia, corresponding to the Sukhothai Zone (the Chanthaburi-Kampong Chhnang Zone). Zircon U-Pb dating yields ages of 208–214 Ma (the Late Triassic) for granite bodies except for the Khao Cha Mao granitic body, which dates to 55 Ma. The former age corresponds to the collision time of the Sibumasu and Indochina terranes, and the latter age is likely related to the collision time of the Indian and Eurasian continents.
Umezawa Yu, Toyoshima Kanae, Yu Saitoh, Takeda Shigenobu, Tamura Kei, Tamaya Chiaki, Yamaguchi Akira, Yoshimizu Chikage, Tayasu Ichiro and Kawamoto Kazuaki : Evaluation of origin-depended nitrogen input through atmospheric deposition and its effect on primary production in coastal areas of western Kyushu, Japan, Environmental Pollution, Vol.291, No.118034, 2021.
(要約)
Long term monitoring of atmospheric wet and dry depositions and associated nutrients fluxes was conducted on the coast of Japan facing the East China Sea continuously for 1 year and 2 months, with the origin of air mass investigated based on isotope analyses (Sr, Nd, and NO). During the same period, intensive observations of ocean conditions and the chemical composition of sinking particles collected using sediment traps were conducted to investigate the effects of atmospheric deposition-derived nutrients on phytoplankton blooms. Dry-deposition-derived nutrient inputs to the surface ocean were larger during autumn to spring than in summer due to the effect of continental air mass occasionally carrying Asian dust (yellow sand). However, these nutrients fluxes were limited (1.1-1.5 mg-N m day on average) and didn't appear to cause phytoplankton blooms through the year. Although average dissolved inorganic nitrogen (DIN) concentrations in rainwater were lower in oceanic air masses compared to continental air masses, wet-deposition-derived nutrient inputs to the surface ocean on rainy days during the summer (26.0 mg-N m day on average) were large due to higher precipitation from oceanic air masses. Wet-deposition-derived nutrients significantly increased nutrient concentrations in the surface ocean and seemed to cause phytoplankton blooms in the warm rainy season when nutrients in the surface were depleted due to increased stratification. The increase in phytoplankton biomass was reflected in increased particle sinking into the bottom layer, as well as changing chemical characteristics. The supply of flesh phytoplankton-derived labile organic matter into the bottom layer could be expected to promote rapid bacterial decomposition and contribute to the formation of hypoxic water masses in early summer when the ocean was strongly stratified. Atmospheric deposition-derived nutrients in East Asia will have important impacts on not only the oligotrophic outer ocean but also surrounding coastal areas in the warm rainy season.
(キーワード)
Environmental Monitoring / Japan / Nitrogen / Oceans and Seas / Phytoplankton
Yu Saitoh, Tsuyoshi Ishikawa and Masaharu Tanimizu : Sr-Nd-Pb isotope systematics of fine sediments from the modern rivers in SW Japan: Implications for sediment provenance of the Northwest Pacific, Journal of Asian Earth Sciences: X, Vol.3, No.100029, 2020.
Takanori Nakano, Katsuyuki Yamashita, Atsushi Ando, Soichiro Kusaka and Yu Saitoh : Geographic variation of Sr and S isotope ratios in bottled waters in Japan and sources of Sr and S, The Science of the Total Environment, Vol.704, 135449, 2020.
(要約)
The geographic distribution of the stable isotope ratio of Sr (Sr/Sr) is useful for identifying the provenance of drinking water, organisms, and agricultural products. To explore how environmental factors influence this ratio, we determined the Sr/Sr, sulfur isotope ratio (δS), and elemental composition of 208 commercially available bottled waters in Japan, and compared them with the Sr/Sr values of groundwater, rainwater, rocks, and vegetables from similar localities. We classified the bottled waters into seven categories based on the geology of their source aquifers. The Sr/Sr and concentrations of several elements (Ca, K, Si, Rb, and Ba) of the bottled waters differed with the aquifer rock type and were well correlated with the Sr/Sr of reported spring waters, indicating that bottled water, like other groundwater, reflects the lithology and chemistry of its aquifer. The Sr/Sr of bottled water, taken as a proxy for groundwater, showed regional variations consistent with those of rocks and vegetables, demonstrating that an Sr/Sr map of water and agricultural products has value for determining the production areas of these substances. However, the value and range of Sr/Sr differed among these three materials, and the degree of the difference between groundwater and rock depended on the rock type. An analysis of geochemical data from rocks and rainwater suggests that groundwater contains Sr and additional S derived from atmospheric sources such as rainwater and sea salt aerosols. The atmospheric contribution of Sr to groundwater is greatest in areas of siliceous sedimentary rocks with low Sr concentrations and high resistance to weathering. A weak correlation of δS of bottled waters with Sr/Sr indicates the usefulness of maps of combined Sr and S isotope ratios for groundwater provenance. This study shows that for accurate provenance determinations of groundwater, organisms, and agricultural products, it is essential to better quantify the contributions of Sr and S from the atmosphere as well as from rocks and human activities.
(キーワード)
Drinking Water / Environmental Monitoring / Japan / Strontium Isotopes / Sulfur Isotopes / Water Pollutants, Chemical
Ohta Tamihisa, Shin Ki-Cheol, Yu Saitoh, Nakano Takanori and Hiura Tsutom : The effects of differences in vegetation on calcium dynamics in headwater streams, Ecosystems, Vol.21, No.7, 1390-1403, 2018.
(キーワード)
Ecology / Environmental Chemistry / Ecology, Evolution, Behavior and Systematics
Jun Matsubayashi, Yu Saitoh, Yutaka Osada, Yoshitoshi Uehara, Junko Habu, Tsuyoshi Sasaki and Ichiro Tayasu : Incremental analysis of vertebral centra can reconstruct the stable isotope chronology of teleost fishes, Methods in Ecology and Evolution, Vol.8, 1755-1763, 2017.
(キーワード)
Ecological Modelling / Ecology, Evolution, Behavior and Systematics
Yu Saitoh, Tsuyoshi Ishikawa, Masaharu Tanimizu, Masafumi Murayama, Yurika Ujiie, Yuzuru Yamamoto, Kohtaro Ujiie and Toshiya Kanamatsu : Sr, Nd, and Pb isotope compositions of hemipelagic sediment in the Shikoku Basin: implications for sediment transport by the Kuroshio and Philippine Sea plate motion in the late Cenozoic, Earth and Planetary Science Letters, Vol.421, 47-57, 2015.
Yu Saitoh and Fujio Masuda : Spatial change of grading pattern of subaqueous flood deposits in Lake Shinji, Japan, Journal of Sedimentary Research, Vol.83, 221-233, 2013.
13.
Yu Saitoh, Tamura Toru, Kodama Yoshinori and Nakano Takanori : Strontium and neodymium isotopic signatures indicate the provenance and depositional process of loams intercalated in coastal dune sand, western Japan, Sedimentary Geology, Vol.236, 272-278, 2011.
Yu Saitoh and Fujio Masuda : Miocene sandstone of continental origin on Iriomote Island, southwest Ryukyu arc, Eastern Asia, Journal of Asian Earth Sciences, Vol.24, No.2, 137-144, 2004.
学術論文(紀要・その他):
1.
Yu Saitoh, Tamura Toru and Fujio Masuda : Hyperpycnal-flow deposits from the Miocene continental delta complex in the Ryukyu islands arc, southwest Japan, Mega-deltas of Asia - Geologic evolution and human impact, 262-268, 2005.
Yu Saitoh : Data Report: grain size distribution of the late Cenozoic hemipelagic mud from Site C0011, Proceedings of the Integrated Ocean Drilling Program, Vol.333, No.203, Apr. 2014.