38 research outputs found
Formation process and metamorphism on R chondrite parent body based on distribution of rare earth elements, Th and U.
No full text第8回極域科学シンポジウム/個別セッション：[OA] 南極隕石
12月6日（水）国語研究所 2階講堂
The Eighth Symposium on Polar Science/Ordinary sessions: [OA]
The Eighth Symposium on Polar Science/Ordinary sessions: [OA Antarctic meteorites
Wed. 6 Dec./2F Auditorium, National Institute for Japanese Language and Linguisticsconference objec
Formation process and metamorphism on R chondrite parent body based on distribution of rare earth elements, Th and U.
No full textChemical and isotopic characterization of Antarctic meteorites: The chemical and isotopic effects of thermal processing and terrestrial weathering on the (re-)distributions of trace elements in chondrites
No full textMy PhD research aims to encompass a detailed chemical and isotopic characterization of “well-preserved” Antarctic meteorites to improve our understanding of the (re-)distribution of various trace elements in specific meteorite types and the effects of the (re-)distribution on radiogenic isotope systematics. As Antarctic meteorites can be affected by alteration, prior to the investigation of the elemental distribution in meteorites and the isotopic effects of the (re-)distribution, the first task of this work has been dedicated to assessing the effects of Antarctic alteration on the chemical and isotopic compositions of ordinary chondrites, the most abundant class of meteorites, and more specifically on H group of ordinary chondrites. The main focus is placed on the systematic study of rare earth elements including their isotope systematics such as Sm-Nd and Lu-Hf.This PhD thesis first demonstrates that the effects of Antarctic alteration on the Sm-Nd and Lu-Hf systems in bulk H chondrites are generally limited and thus the Sm-Nd and Lu-Hf systems preserve their original compositions during Antarctic alteration. Secondly, the underlying mechanism of Antarctic alteration observed in the first part of the PhD study is investigated using in-situ measurement techniques including state-of-the-art laser ablation-inductively coupled plasma-time of flight-mass spectrometry (LA-ICP-TOF-MS). Simultaneously, the potential of LA-ICP-TOF-MS as a novel technique to study the elemental distribution is examined and evaluated. Finally, the distribution of lithophile elements among the constituent minerals in H chondrites is documented at the microscale and their re-distribution during thermal metamorphism in the parent body(ies), i.e. the thermal effects of the lithophile element distribution are quantified and discussed, with a direct link to the heterogeneity recorded in the Sm-Nd and Lu-Hf isotope systematics of bulk chondrites. Overall, this thesis confirms the generally pristine nature of Antarctic meteorites and describes the thermal processes that took place in the parent bodies of ordinary chondrites.Cette thèse de doctorat vise à apporter une caractérisation chimique et isotopique détaillée des météorites antarctiques considérées comme « bien conservées" afin d'améliorer notre compréhension de la (re-)distribution de divers éléments en traces dans des types de météorites spécifiques ainsi que pour les systèmes isotopiques radiogéniques. Comme les météorites antarctiques peuvent être affectées par l'altération, avant l'étude de la distribution élémentaire dans les météorites et les effets isotopiques de la (re-)distribution, la première tâche de ce travail a été consacrée à l'évaluation des effets de l'altération antarctique sur les compositions chimiques et isotopiques des chondrites ordinaires, la classe la plus abondante de météorites, et plus précisément du groupe H des chondrites ordinaires. L'accent est mis sur l'étude systématique des éléments des terres rares, y compris leur systématique isotopique Sm-Nd et Lu-Hf.Ce travail démontre d'abord que les effets de l'altération antarctique pour les systèmes Sm-Nd et Lu-Hf dans les chondrites de type H sont généralement limités et donc que ces systèmes conservent leurs compositions d'origine lors de l'altération antarctique. Deuxièmement, le mécanisme sous-jacent de l'altération antarctique a été étudié à l'aide de techniques de mesure in situ, notamment l'ablation laser et la spectrométrie de masse plasma-temps de vol à couplage inductif (LA-ICP-TOF -MS). Simultanément, le potentiel du LA-ICP-TOF-MS en tant que nouvelle technique pour étudier la distribution élémentaire a été examiné et évalué. Enfin, la distribution des éléments lithophiles parmi les minéraux constitutifs des chondrites H est documentée à l'échelle microscopique et leur redistribution lors du métamorphisme thermique dans le ou les corps parents. Ainsi, les effets thermiques de la distribution des éléments lithophiles sont quantifiés et discutés, avec un lien direct avec l'hétérogénéité enregistrée dans la systématique isotopique Sm-Nd et Lu-Hf des chondrites. Dans l'ensemble, cette thèse confirme la nature généralement intacte des météorites antarctiques et identifie les processus thermiques qui ont eu lieu sur les corps parents des chondrites ordinaires.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe
The effect of fluid alteration in Antarctic chondrites
No full textThe 14th Symposium on Polar Science/Ordinary sessions [OA] Antarctic Meteorite, Tue. 14 Nov. / 3F Multipurpose Conference room, Institute of Statistical Mathematicsconference objec
Measurement of Water Vapor Concentration in Narrow Channel of PEFC Using Fiber-Optic Sensor Based on Laser Absorption Spectroscopy
No full textDevelopment of fiber-optic laser absorption spectroscopy technique for gas concentration measurement in fuel cell
No full textChrome-rich spinels in micrometeorites from modern Antarctic sedimentary deposits
No full textEach year, approximately 5000 tons of extraterrestrial material reaches the Earth's surface as micrometeorites, cosmic dust particles ranging from 10 to 2000 μm in size. These micrometeorites, collected from diverse environments, mainly deep-sea sediments, Antarctic ice, snow and loose sediments, and hot deserts, are crucial in understanding our Solar System's evolution. Chrome-rich spinel (Cr-spinel) minerals have gained attention as proxies for studying the extraterrestrial flux in sedimentary deposits, because these robust minerals occur, in various extraterrestrial materials, with compositions characteristic of their parent bodies. A total of 27 Cr-spinel bearing micrometeorites within the size range of 185–800 μm, were identified from approximately 6000 micrometeorites from the Transantarctic Mountains (n = 23) and the Sør Rondane Mountains (n = 4), in Antarctica, containing Cr-spinel (8–120 μm), were examined in this study for geochemical composition and high-precision oxygen isotope ratios to assess alteration and identify potential parent bodies.
Oxygen isotopes in the micrometeorite groundmass and in Cr-spinel grains reveal a predominance of ordinary chondritic precursors, with only 1 in 10 micrometeorites containing Cr-spinel minerals showing a carbonaceous chondritic signature. This may be further confirmed by an elevated Al content (> 12 wt% Al2O3) in Cr-spinel from specific carbonaceous chondrite types, but a more extensive dataset is required to establish definitive criteria. The first Cr-spinel bearing particle, in an Antarctic micrometeorite, that can be linked to R-chondrites based on oxygen isotopes, has been documented, demonstrating the potential for R-chondrites as a source of chrome-rich spinels. The study also highlights the potential for chemical modifications and alteration processes that Cr-spinel minerals may undergo during their time on the parent body, atmospheric entry, and terrestrial residence.
In the context of the broader micrometeorite flux, the results align with previous findings, showing a consistent contribution of micrometeorites containing Cr-spinel minerals related to ordinary chondrites over the past 2 to 4 million years. This is however a small fraction (∼ 1 %) of the total micrometeorite flux. The study further confirms that Cr-spinel minerals recovered from sedimentary deposits serve as valuable proxies for tracking events related to ordinary chondritic or achondritic materials. However, it is emphasized that Cr-spinel minerals alone cannot serve as exclusive indicators of the overall extraterrestrial flux, especially during periods dominated by carbonaceous chondritic dust in the inner Solar System. To comprehensively understand the complete extraterrestrial flux, additional proxies are needed to trace dust-producing events associated with various Solar System objects. The intricate nature of Cr-spinel compositions, and the potential for alteration processes emphasize the need for further research to refine our understanding of these extraterrestrial markers
Quantitative elemental mapping of chondrites using LA-ICP-TOF-MS
No full textThe 15th Symposium on Polar Science/Ordinary sessions [OA] Antarctic Meteorite, Thu. 5 Dec. / 3F Conference room, The Institute of Statistical Mathematicsconference outpu
