Date: 16:00-18:00, Friday, February 7, 2020
Place: 3F, Lecture room, Main Chemistry Build.
Speaker：Zhenghao Zhao, Sota Niki
日 時：2020年2月7日（金）16:00-18:00
場 所：化学本館3階講義室
講演者：趙 政皓、仁木創太
講演者1：趙 政皓（Zhenghao Zhao）
タイトル： The Pressure-Induced Spin-Crossover of Cobalt Octahedral Complexes
Spin-crossoverあるいはspin transitionは、圧力・温度・光で誘起する金属錯体におけるスピン状態の変化である。主にd4からd7までの電子配置を持つ八面体錯体に観察される。スピン状態の変化は物質の磁性や結晶構造などの性質に影響を与えるため、鉱物の形成にも影響すると考えられる。本研究では、コバルトの八面体錯体を持つ結晶体のspin-crossoverによる相転移を研究し、その相転移によって電磁学的な性質と結晶構造はどうのように変化するか、配位子がどうのようにspin-crossoverに影響を与えるかを明らかにすることを目的にする。今回は、今まで行ったCoCl2·6H2Oを対象にした10GPa以下の加圧実験とその結果について発表する。
講演者2：仁木創太（Sota Niki）
タイトル： レーザーアブレーションICP質量分析法を用いたコノドントの元素イメージング分析及び U–Th–Pb年代測定
Title: Elemental imaging analysis and U–Th–Pb dating of conodonts using Laser Ablation-ICP-Mass Spectrometry
Depositional ages of sedimentary units are commonly constrained by radiometric dating of minerals (e.g. zircon) from ash beds and thus, without finding ash beds, determining the depositional age of sedimentary units is challenging (Greene et al., 2018).
Because of the absence of ash beds, the timescale for the Norian stages of the Triassic series is imperfectly constrained by radiometric dating (e.g. Furin et al., 2006). There is only a few geochronological constraints on the Norian stage, for instance, zircon U–Pb dating of the impact melt rock from the Manicouagan impact structure (Ramezani et al., 2005) and a magnetostratigraphic comparison (Olsen et al., 2017), and the timescale of marine sections have not been directly constrained.
In this study, U–Th–Pb dating of conodont samples (Misikella posthernsteini) collected from the Pizzo Mondello section (Rigo et al., 2018) were conducted using Laser Ablation-ICP-Mass Spectrometry. Conodonts are one of the index fossils found in marine deposits and they are composed of apatite which is rich in uranium and thorium. For precise and accurate U–Th–Pb dating of fossils, least-altered and radiogenic-Pb-rich regions should be identified by elemental imaging analysis (e.g. Greene et al., 2018). Considering from the results of the elemental imaging analysis, conodont samples analyzed in this study were altered and poor in radiogenic Pb. The 207Pb/206Pb and 238U/206Pb ratios obtained by using LA-MC-ICP-MS imply that the sample have experienced the post-fossilization-alteration recently.