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FeNi metal condensation and evolution in the Early Solar System: a study of germanium isotopes and siderophile elements in Ordinary and Bencubbinite primitive chondrites

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posted on 2023-01-25, 02:20 authored by Guillaume Jean Florin

The formation and subsequent chemical evolution of FeNi metal phases is critical for understanding the development of the early Solar System. Despite numerous studies on metal phases in chondrites, the effect of metal condensation at moderate temperatures, as well as of metal heating and oxidation in nebular and protoplanetary environment, is still under debate. By using a combined approach of germanium isotopic quantification and siderophile in-situ measurements in bulk and separated phases of Bencubbinites carbonaceous chondrites (CB) and ordinary chondrites, this thesis aims to provide new constraints on: (1) the formation of metal via condensation and metallic precursors melting and (2) the processes that can account for the elemental and isotopic difference between the H, L and LL chondrites and metal evolution with metamorphism. The results show that the two groups of CB are distinguishable using  𝝳74/ 70Gebulk, providing insights into kinetic and equilibrium condensation processes. Variations in 𝝳74/70Ge during metal condensation are shown to be the result of evaporation / recondensation processes that are not recorded by major or refractory elements. A large variation in siderophile element content in the metal of H primitive ordinary chondrites has been identified, as well as a positive 𝚫74/ 70GemetaI-silicates• This suggests local oxidation state variation and metal-silicate interactions during heating event(s) in the disk. The thesis also highlights that the H, Land LL groups are resolvable with 𝝳74/70Ge of bulk and metal. These variations are positively correlated with 𝚫17O and  % Fa across the ordinary chondrites sequence and suggests the accretion of an increasing proportion of oxidising components with a high 𝝳74/70Ge and 𝚫17O composition from H to L to LL groups. Because the oxidising component contains Ge it suggests that it cannot be ice or water but more likely a silicate phase. These conclusions highlight the high potential of germanium isotopes to record processes leading to metal formation and evolution.

History

Table of Contents

Chapter 1: Introduction -- Chapter 2: Sample Preparation and Analytical Techniques -- Chapter 3: Processes of Metal Formation by Condensation -- Chapter 4: Processes of Metal Evolution by Heating Before and After Accretion --Chapter 5: Role of Oxidizing Processes on the Evolution of Metal -- Chapter 6: Conclusions, Ongoing Project and Perspectives -- References

Notes

Cotutelle thesis in conjunction with the Centre de Recherches Petrographiques et Geochimiques, Lorraine University

Awarding Institution

Macquarie University ; Lorraine University

Degree Type

Thesis PhD

Department, Centre or School

Department of Earth and Environmental Sciences ; Centre de Recherches Petrographiques et Geochimiques

Year of Award

2020

Principal Supervisor

Tracy Rushmer

Additional Supervisor 1

Beatrice Luais

Additional Supervisor 2

Olivier Alard

Rights

Copyright: Guillaume Jean Florin Copyright disclaimer: https://www.mq.edu.au/copyright-disclaimer

Language

English

Extent

246 pages