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Oral presentation

An Analytical technique of trace elements using LA-ICP-MS for tephra identification

Kagami, Saya; Yokoyama, Tatsunori; Umeda, Koji*

no journal, , 

Tephrochronology is one of the geochronological techniques for Quaternary and generally used as well as radiocarbon dating. A catalogue of wide-spread tephras provides fundamental criteria for the establishment of a regional chronostratigraphy. Tephras have been identified by petrographic characteristics, types of volcanic glass shards in tephra, and major elements compositions of them. Major element analyses of volcanic glass shards are usually carried out by EPMA. Recently, it has been reported that the some tephras which were quite similar to others in major element compositions were distinguishable by trace element compositions. Although trace element data of volcanic glass shards are important for tephra identification, the data are still lack in a catalogue of wide-spread tephras. To measure trace element abundances of the glass shards, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a powerful method because individual glass shards can be analyzed. In this study, we performed trace element analysis of tephras using LA-ICP-MS at Tono Geoscience Center, JAEA. We analyzed the concentration of 41 elements with the internal standard element of Si and two calibration standards of NIST SRM 612 and 614. Three tephra samples were prepared: Aso-4, Aira-Tn (AT), and Akogi (identified to Znp-Ohta) tephras. While a fused glass bead of Aso-4 was prepared, the others were mounted on epoxy resin. In Aso-4 and AT tephra samples, the concentrations of trace elements (Rb, Sr, Y, Zr, Ba, La, and Ce), by which tephras are especially identified, were consistent with those in the previous studies (RSD:$$sim$$10%). We obtained the pattern of trace element compositions of Akogi tephras, which was similar to that of Znp-Ohta tephras. This analytical method will contribute to establish the detailed catalogue of tephras.

Oral presentation

An Analytical technique for simultaneously estimating crystallization age and temperature of zircon using LA-ICP-MS

Yokoyama, Tatsunori; Yuguchi, Takashi*; Sakata, Shuhei*; Ishibashi, Kozue*; Ogita, Yasuhiro*; Ito, Daichi*; Ono, Takeshi*; Kagami, Saya; Mitsuguchi, Takehiro; Sueoka, Shigeru

no journal, , 

Dating and trace elements analysis of zircons provide us the evidences of past thermal history about their growth events, such as timing and temperature of magmatism and crystallization. In granitic rocks, because the proposed closure temperature of zircon U-Pb ($$>$$900 $$^{circ}$$C) is often higher than crystallization temperature of the zircon, the zircon U-Pb age means the timing of crystallization. To clarify the growth history of granitic pluton, Yuguchi et al. (2016) performed the observation of internal structure of zircon (collected from the Toki granite, central Japan) using cathodoluminescence, deriving crystallization temperature and age using Ti-in-zircon thermometry and U-Pb dating. It is important to discuss the emplacement by such an approach to understand the history of upheaval and exhumation of igneous complex. In this study, for simultaneously estimating crystallization age and temperature of zircon, we performed U-Pb isotopic analysis and quantitative analysis of Titanium, in the same position of zircon, using LA-ICP-MS after the cathodoluminescence observation. As preliminary experiments, we analyzed zircons collected from Japan (e.g., Okue, Tono, Toki and Kurobegawa granites) to estimate their thermal history. We could estimate the crystallization ages and temperatures of zircons of Okue (556-946$$^{circ}$$C in 11.1-16.1 Ma), Tono (613-901$$^{circ}$$C in 110.2-127.4 Ma), Toki (575-734$$^{circ}$$C in 69.4-79.9 Ma) and Kurobegawa (636-779$$^{circ}$$C in 0.46-1.85 Ma), respectively.

Oral presentation

Sorption behaviors of Cs and Eu onto altered rock formed around fault

Watanabe, Yusuke; Kashiwaya, Koki*

no journal, , 

no abstracts in English

Oral presentation

Multiple groundwater dating conducted at Mizunami URL

Hasegawa, Takuma*; Nakata, Kotaro*; Tomioka, Yuichi*; Ota, Tomoko*; Okamoto, Shunichi*; Hama, Katsuhiro; Watanabe, Yusuke; Iwatsuki, Teruki

no journal, , 

no abstracts in English

Oral presentation

Leaching behavior of iodine anion from metakaolinite-sodium-silicate-based geopolymer

Kozai, Naofumi; Utsunomiya, Satoshi*; Onuki, Toshihiko*

no journal, , 

$$^{129}$$I is one of the most important fission products for safety assessment of radioactive waste repositories. This study investigated basic characteristics of a cement-alternative material candidate, "geopolymer (GP)", on iodine (I$$^{-}$$ and IO$$_{3}$$$$^{-}$$) confinement. It was found that representative GP, metakaolinite- sodium silicate - based GP, has no ability to chemically retain those iodine anions. I$$^{-}$$ was easily leached from GP solidified bodies. Approximately 80% of IO$$_{3}$$$$^{-}$$ was retained by GP solidified bodies, which was probably due to physical confinement in the polymer structure. Amount of iodine anions that can be solidified in GP solidified bodies was small since iodine anions do not much dissolve in the liquid used for GP synthesis. However, we also found that a larger amount of iodine anions can be solidified by iodine anions adsorbing layered double hydroxide is solidified in geopolymer.

Oral presentation

Effect of ionic radius on the adsorption structure of various

Yamaguchi, Akiko; Okumura, Masahiko; Takahashi, Yoshio*

no journal, , 

no abstracts in English

Oral presentation

Machine learning molecular dynamics studies of clay minerals

Okumura, Masahiko; Kobayashi, Keita*; Yamaguchi, Akiko; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko

no journal, , 

no abstracts in English

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