Chemical 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

• Main Author: Maeda, Ryoga
• Other Authors: Debaille, Vinciane, Goderis, Steven, Claeys, Philippe, Mattielli, Nadine, Gao, Yue, Alexander, Conel, Lee, Martin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universite Libre de Bruxelles 2023
• Subjects: Sciences de la terre et du cosmos; Géochimie; Meteorite; Isotope; Antarctica; Antarctic; Antarc*
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/356650; https://dipot.ulb.ac.be/dspace/bitstream/2013/356650/3/Table_of_contents_Ryoga_Maeda_final_ULB.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/356650/5/ContratDiMaeda.pdf; https://dipot.ulb.ac.be/dspace/bitstream/2013/356650/4/PhD_thesis_Ryoga_Maeda_final_ULB.pdf

My 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 ...