A 3-D Magnetotelluric Study of the Slave Craton Lithosphere, NW Canada
Notice bibliographique
Résumé
Archean cratons are comprised of thick, stable continental lithosphere that has persisted for billions of years owing to their isopycnicity (i.e. near neutral buoyancy) and higher viscosity than the surrounding mantle. These regions host diamonds at depths greater than 150 km due to the relatively cold temperatures found in the depth range where pressure is high enough for diamonds to be stable. Because of this, understanding the deep structure of cratonic lithosphere is important for regional diamond exploration. In this thesis previously collected magnetotelluric (MT) data were used to produce a 3-D resistivity model of the Slave craton's lithosphere. The resolution of this resistivity model was rigorously tested. Important features of the model and their implications include: (1) A region of low resistivity (< 10 Ωm) at a depth of 100 km beneath the Lac de Gras kimberlite field in the central Slave craton, which was interpreted as a layer of high density saline fluids that were emplaced from a Mesozoic subduction event. Phlogopite and grain boundary sulphides also remain as possible interpretations for the cause of the low resistivity (< 10 Ωm). However, none of these proposed interpretations are without their flaws. Fluids in the mantle would be positively buoyant and reactive suggesting that it would be difficult to retain fluids from the Mesozoic over long time periods. Large quantities of phlogopite would be required (> 20% volume fraction) to produce the low resistivity observed (< 10 Ωm), which is not strongly supported by observations in xenoliths and there is little experimental work on grain boundary sulphides in the mantle. This region of low resistivity was previously observed at depths of 80 - 120 km by Jones et al. (2003). Previous interpretations of this conductor invoked graphite films as an explanation, but it is unlikely that graphite films are stable at these depths. The spatial correlation between the low resistivity layer and the Lac de Gras kimberlite field could be the result of kimberlite magmas following zones of weakness in the lithosphere as a result of the metasomatism caused by the slab-derived fluids. (2) The resistivity model also showed that beneath the entire Slave craton the lithosphere-asthenosphere boundary (LAB) is at a depth of at least 200 km. Determining the depth to the LAB is important as this can determine the size of the diamond stability field within the lithosphere, which is used in regional diamond targeting. (3) The upper mantle resistivity can be interpreted as requiring a low water content on the order of 10 - 150 ppm by weight in the depth range 100 -170 km. Below these depths the lithosphere appears to be dry (< 5 ppm). The dry base of the lithosphere may act as a resistant boundary preventing the cratonic root from being eroded by the underlying asthenosphere.
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 machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».