Tellurium isotope compositions of chondritic meteorites and terrestrial samples – tracing volatile element fractionation during nebular and parent body processes
File(s)
Author(s)
Morton, Elin
Type
Thesis
Abstract
Despite numerous investigations in the past decades, the processes that governed the distribution and behaviour of volatile element in the protoplanetary disk and on meteorite parent bodies are still poorly understood. These processes are important, as the volatile element systematics provide a valuable record on the formation and early evolution of our solar system, and on the origin and delivery of the constituents necessary for the development of terrestrial life. This study aims to investigate these processes through stable isotope investigations of the moderately volatile and chalcophile to siderophile element Te in chondritic meteorites and terrestrial samples. To this end, new analytical methods that use a 125Te-128Te double spike and MC-ICP-MS were developed and validated during this study. These methods were subsequently applied to determine the Te isotope compositions and concentrations of a suite of 54 chondritic meteorites. The carbonaceous chondrites define a positive correlation between Te isotope compositions and concentrations, whereby both values decrease in the order CI > CM > CV-CO > CR. This reflects a nebular trend of variable mixing between a volatile-rich, CI-like matrix component and a volatile-depleted, chondrule-related component. In contrast, the Te isotope compositions and concentrations of the ordinary and enstatite chondrites record the impact of thermal alteration on the meteorite parent bodies. In particular, this study presents a model which shows that the distinct Te systematics of equilibrated and unequilibrated enstatite chondrites reflect loss of volatile Te from the hot parent body interiors, and addition of this mobilised Te to the cooler exterior layers, respectively. Tellurium isotope data for terrestrial rocks and chondritic meteorites from this and previous studies indicate that CI, CM, H, L, EH, and EL chondrites overlap with the current best d130TeBSE estimate of 0.66 ± 0.06‰. Consequently, these meteorite groups are possible contributors to the Earth’s late veneer.
Version
Open Access
Date Issued
2022-11-04
Date Awarded
01/01/2023
License URL
Advisor
Rehkamper, Mark
Sponsor
Hans Rausing foundation
Publisher Department
Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)