28 research outputs found
Geologic connection between Dronning Maud Land and Enderby Land
The Tenth Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Wed. 4 Dec. / Entrance Hall (1st floor), National Institute of Polar Researc
The Quaternary Kurobegawa Granite: an example of a deeply dissected resurgent pluton
H.I thank M. Yukawa for her help with sample preparation and LA-ICP-MS data collection, and Y. Hirata for sampling. U-Pb ages were calculated using an Excel spreadsheet provided by S. Sakata. English was improved by M. Coble. Comments by O. Bachmann, J. Wotzlaw and an anonymous reviewer were helpful to improve the manuscript. The Kansai Electric Power Co., Inc., and the Japan Ministry of the Environment gave us permission for the sampling. This work was partly supported by JSPS KAKENHI Grant Number JP16K05617. AC acknowledges the research grant "Beca Puente" and the financial support of a "Plan Propio" grant from the University of Granada Vicerrectorate of Research and Transfer. This is the IBERSIMS publication n. 88.The Quaternary Kurobegawa Granite, central Japan, is not only the youngest known granitic pluton
exposed on the Earth’s surface, it is one of few localities where both Quaternary volcanics and
related plutons are well exposed. Here, we present new zircon U–Pb ages together with whole rock
and mineral geochemical data, revealing that the Kurobegawa Granite is a resurgent pluton that
was emplaced following the caldera-forming eruption of the Jiigatake Volcanics at 1.55 ± 0.09 Ma.
Following the eruption, the remnant magma chamber progressively cooled forming the voluminous
Kurobegawa pluton in the upper crust (~ 6 km depth) until ~ 0.7 Ma when resurgence caused rapid
uplift and erosion in the region. This is the first study to document the detailed spatiotemporal
evolution of resurgent pluton for a Quaternary caldera system. Our new findings may contribute
significantly to understanding the fate of active caldera systems that can produce supereruptions.Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
Japan Society for the Promotion of Science
Grants-in-Aid for Scientific Research (KAKENHI) JP16K05617University of Granada Vicerrectorate of Research and Transfe
Matuyama-Brunhes boundary age constrained by SHRIMP U-Pb zircon dating of a widespread tephra
U-Pb geochronology in western part of the Rayner Complex, East Antarctica
第2回極域科学シンポジウム/第31回極域地学シンポジウム 11月17日(木) 国立極地研究所 2階大会議室前フロ
New highly radioactive particles derived from Fukushima Daiichi Reactor Unit 1 : Properties and environmental impacts
A contaminated zone elongated toward Futaba Town, north-northwest of the Fukushima Daiichi Nuclear Power Plant (FDNPP), contains highly radioactive particles released from reactor Unit 1. There are uncertainties associated with the physio-chemical properties and environmental impacts of these particles. In this study, 31 radioactive particles were isolated from surface soils collected 3.9 km north-northwest of the FDNPP. Two of these particles have the highest particle-associated 134+137Cs activity ever reported for Fukushima (6.1 × 105 and 2.5 × 106 Bq per particle after decay-correction to March 2011). The new, highly-radioactive particle labeled FTB1 is an aggregate of flaky silicate nanoparticles with an amorphous structure containing ~0.8 wt% Cs, occasionally associated with SiO2 and TiO2 inclusions. FTB1 likely originates from the reactor building, which was damaged by a H2 explosion, after adsorbing volatilized Cs. The 134+137Cs activity in the other highly radioactive particle labeled FTB26 exceeded 106 Bq. FTB26 has a glassy carbon core and a surface that is embedded with numerous micro-particles: Pb–Sn alloy, fibrous Al-silicate, Ca-carbonate or hydroxide, and quartz. The isotopic signatures of the micro-particles indicate neutron capture by B, Cs volatilization, and adsorption of natural Ba. The composition of the micro-particles on FTB26 reflects the composition of airborne particles at the moment of the H2 explosion. Owing to their large size, the health effects of the highly radioactive particles are likely limited to external radiation during static contact with skin; the highly radioactive particles are thus expected to have negligible health impacts for humans. By investigating the mobility of the highly radioactive particles, we can better understand how the radiation dose transfers through environments impacted by Unit 1. The highly radioactive particles also provide insights into the atmospheric conditions at the time of the Unit 1 explosion and the physio-chemical phenomena that occurred during reactor meltdown.Peer reviewe
Particulate plutonium released from the Fukushima Daiichi meltdowns
Traces of Pu have been detected in material released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March of 2011; however, to date the physical and chemical form of the Pu have remained unknown. Here we report the discovery of particulate Pu associated with cesium-rich microparticles (CsMPs) that formed in and were released from the reactors during the FDNPP meltdowns. The Cs-pollucite-based CsMP contained discrete U(IV)O2 nanoparticles,Peer reviewe
Isotopic signature and nano-texture of cesium-rich micro-particles: Release of uranium and fission products from the Fukushima Daiichi Nuclear Power Plant
Highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) provide nano-scale chemical fingerprints of the 2011 tragedy. U, Cs, Ba, Rb, K, and Ca isotopic ratios were determined on three CsMPs (3.79–780 Bq) collected within ~10 km from the FDNPP to determine the CsMPs’ origin and mechanism of formation. Apart from crystalline Fe-pollucite, CsFeSi2O6 · nH2O, CsMPs are comprised mainly of Zn–Fe-oxide nanoparticles in a SiO2 glass matrix (up to ~30 wt% of Cs and ~1 wt% of U mainly associated with Zn–Fe-oxide). The 235U/238U values in two CsMPs: 0.030 (±0.005) and 0.029 (±0.003), are consistent with that of enriched nuclear fuel. The values are higher than the average burnup estimated by the ORIGEN code and lower than non-irradiated fuel, suggesting non-uniform volatilization of U from melted fuels with different levels of burnup, followed by sorption onto Zn–Fe-oxides. The nano-scale texture and isotopic analyses provide a partial record of the chemical reactions that occurred in the fuel during meltdown. Also, the CsMPs were an important medium of transport for the released radionuclides in a respirable form
Adoptive transfer of antithyrotropin receptor (TSHR) autoimmunity from TSHR knockout mice to athymic nude mice
We have recently shown that wild type mice are highly tolerant, whereas thyrotropin receptor (TSHR) knockout (KO) mice are susceptible to immunization with the mouse TSHR, the autoantigen in Graves\u27 disease. However, because TSHR KO mice lack the endogenous TSHR, Graves-like hyperthyroidism cannot be expected to occur in these mice. We therefore performed adoptive transfer of splenocytes from TSHR KO mice into nude mice expressing the endogenous TSHR. Anti-TSHR autoantibodies were detected in approximately 50% recipient mice 4 wk after adoptive transfer of splenocytes (5 × 10 7/mouse) from TSHR KO mice immunized with adenovirus expressing mTSHR A subunit and persisted for 24 wk. Depletion of regulatory T cells by anti-CD25 antibody in the donor mice increased successful transfer rates without increasing antibody levels. Some recipient mice showed transient increases in thyroid-stimulating antibodies and T4 levels 4-8 wk after transfer, but many became thyroid-blocking antibody positive and hypothyroid 24 wk later. Adoptive transfer of splenocytes from naïve TSHR KO mice transiently induced very low antibody titers when the recipient mice were treated with anticytotoxic lymphocyte antigen 4 and antiprogrammed cell death 1 ligand 1 antibodies for 8 wk after transfer. Histologically, macrophages infiltrated the retrobulbar adipose tissues and extraocular muscles in a small fraction of the recipients. Our findings demonstrate successful adoptive transfer of anti-TSHR immune response from TSHR KO mice to nude mice. Although the recipient mice developed only transient and infrequent hyperthyroidism, followed by eventual hypothyroidism, induction of orbital inflammation suggests the possible role of anti-TSHR immune response for Graves\u27 orbitopathy
Geochemical Characterization of Zircon in Fyfe Hills of the Napier Complex, East Antarctica
Ultra-high temperature (UHT) metamorphism plays an essential role in the development and stabilization of continents through accretionary and collisional orogenesis. The Napier Complex, East Antarctica, preserves UHT metamorphism, and the timing is still debated. U–Pb zircon geochronology integrated with rare earth element (REE) and oxygen isotope was applied to a garnet-bearing quartzo-feldspathic gneiss to confirm the timing of UHT metamorphism in Fyfe Hills in the western part of the Napier Complex. The zircons are analyzed using a sensitive high-resolution ion microprobe (SHRIMP). The cathodoluminescence observation and U–Pb ages allowed us to classify the analytical domains into three types: inherited domains (Group I), metamorphic domains (Group II), and U–Pb system disturbed domains (Group III). The REE patterns of Group II are characterized by a weak fractionation between the middle REE and heavy REE, which reinforces the above classification. The 207Pb*/206Pb* ages of Group II have an age peak at 2501 Ma, therefore, the gneiss experienced high temperature metamorphism at 2501 Ma. δ18O of zircons are homogeneous among the three groups (5.53 ± 0.11‰, 5.51 ± 0.14‰, and 5.53 ± 0.23‰), which suggests re-equilibration of oxygen isotopes after metamorphism at ca. 2501Ma under dry UHT conditions
Mechanochemically assisted hydrothermal synthesis of Sn-substituted MFI-type silicates
Substitution of Al atoms in a zeolite framework by catalytic metal atoms has attracted considerable attention because the catalytic behavior can be tuned by the substituted atoms. In the present study, Sn-substituted MFI-type silicates were synthesized using a hydrothermal reaction of an amorphous Si-O-Sn precursor prepared by mechanochemical grinding of SiO2 and Sn(OH)4. The mechanochemical treatment was found to be a key technique for obtaining the amorphous Si-O-Sn precursor, where tetrahedral Sn4+ species were incorporated into the amorphous matrix. The Sn content in the framework of the MFI-type silicates was successfully controlled by the initial HCl/Si molar ratio of the hydrothermal procedures. Optical reflectance measurements revealed that the Sn4+ ions were dispersedly incorporated into the silicate framework while preserving the initial tetrahedrally coordinated species. Infrared results imply that the resulting Sn-substituted MFI-type silicate has Brønsted acid character. Precise control of the Brønsted and Lewis acid properties by Sn doping is a promising approach to the development of novel types of zeolite-based catalytic materials