Ultramafic Alteration and the Cooling of Earth and Mars
Notice bibliographique
Résumé
This thesis deals with the influence of `ultramafic' rocks over the climate of planets. Ultramafic rocks, rich in Mg and Fe, are the most common rocks on Earth but exist primarily in the mantle and rarely outcrop on the surface. They are incredibly unstable under Earth's surface conditions where they are altered via incongruent reactions which form clay minerals, iron oxides, and ultimately release cations to the ocean. Due to their instability, they play an out-sized role in Earth's long-term carbon cycle. My first chapter investigates a hitherto unappreciated mechanism by which ultramafic rocks serve as a carbon sink, through the formation of high-surface-area clays and the resultant burial of organic carbon. I use a combination of mineral weathering models and proxy data to show that this mechanism has contributed to the glaciations of the Palaeozoic (541 - 252 Ma). \n \nUnlike Earth, igneous rocks on the Martian surface are frequently of ultramafic composition. My second chapter argues that the alteration of these Martian ultramafic rocks was fundamental in the cooling of the planet from a habitable surface with liquid water to a cold and icy planet, largely devoid of an atmosphere. I show that the same high-surface-area clay minerals which bury organic carbon on Earth are prevalent enough on Mars to store the bulk of its initial 1-4 bar atmosphere as adsorbed methane. I postulate that this methane was formed abiotically during hydrothermal alteration of ultramafic rocks, a process which is observed in ultramafic systems on Earth. I show that this framework reconciles the histories of \\dc{} and atmospheric loss-to-space on Mars. \n \nMy final chapter quantifies the effects of the alteration of ultramafic and mafic rocks across the Taconic orogeny in Newfoundland, Canada. This collision exposed one of the most well-studied ultramafic bodies on Earth, the Bay of Islands ophiolite, and closely preceded global cooling in the Middle-Late Ordovician (470-445 Ma). I present a new method, leveraging both geochemical analysis and modelling of basin sediments, to infer ancient silicate weathering fluxes. I show that the relative weathering rate in this region increased dramatically during the Taconic orogeny. This method could be applied throughout systems with tectonically-driven changes in surface lithology to build a fuller understanding of the forces which modulate Earth's climate. \n \nMy work asks as many questions as it answers but tries to honestly portray the uncertainties associated with the application of quantitative methods in noisy, geologic systems. I hope that in trying to meaningfully constrain these processes I plant seeds of inquiry from which myself and others can one day make more concrete statements of the cause and effect between tectonics and climate.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».