Chemical and isotopic characterization of Antarctic meteorites: The chemical and isotopic effects of thermal processing and terrestrial weathering on the (re-)distribution of trace elements in chondrites

Research output: ThesisPhD Thesis

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Abstract

Meteorites, any natural solid objects from interplanetary space that survived their passage through Earth’s atmosphere and reached the surface, represent the only large volume of extraterrestrial material available on the Earth today. These precious extraterrestrial samples retain critical information regarding the Solar System processes, and thus they have been investigated from various research perspectives such as chemistry, mineralogy, and petrology, to refine our understanding of the history of the Solar System. Since the first systematic
search for meteorites in Antarctica was successfully conducted in 1969, more than 41,000 meteorites have been collected in Antarctica, which today constitute more than 60% of the population of meteorites by number. Moreover, Antarctic meteorites include many “rare” types of meteorites such as martian and lunar meteorites, and hence the Antarctic meteorite collection plays a pivotal role for cosmochemistry. Before these meteorites were collected in Antarctica, they were buried in the ice sheets for a long time, on average on the order of hundreds of thousands of years. This burial and the cold and dry environment in Antarctica better protect them from terrestrial weathering relative to residence in hot desert environments, where meteorites generally retain for tens of thousands of years or less. Nevertheless, following their long residence time, even Antarctic meteorites can be still altered mineralogically and chemically to some extent, which means that information on their parent bodies and the processes they underwent was modified and lost. Therefore, the effects of Antarctic weathering have been assessed extensively to determine whether or not the results obtained represent the original information. However, as the mechanisms and processes involved vary widely from environment to environment, the underlying mechanisms of the alteration and weathering affecting meteorites remain relatively poorly constrained.

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 the thermal processes that took place in the parent bodies of ordinary chondrites
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
  • Université libre de Bruxelles
Supervisors/Advisors
  • Goderis, Steven, Supervisor
  • Debaille, Vinciane, Supervisor, External person
  • Claeys, Philippe, Supervisor
Award date6 Mar 2023
Publication statusPublished - 2023

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