The Evolution of the Grenville Province in the Mattawa Region of Ontario: Evidence from Neodymium and Constraints from Aeromagnetic Data
Notice bibliographique
Résumé
Approximately eighty new neodymium model ages were determined on grey orthogneisses in the Mattawa region of Ontario and were used to develop a Grenvillian tectonic model in the region. A residual-magnetic field map developed from aeromagnetic data provides an additional constraint on the terranes mapped based on Nd-model ages. The field area was divided into three sections: the northern section, the Mattawa klippe, and the southern section. The objectives of mapping in the northern section were two-fold: 1) to map the location of erosional remnants of the allochthon boundary thrust (ABT) and 2) to test the hypothesis that northwestward thrusting of the ABT over the parautochthonous belt caused decollement of a magmatically reworked Archean terrane, creating a duplex thrust sheet and consequent northwestward thrusting of the magmatically reworked Archean parautochthon. Two allochthonous units previously mapped in this region are the Lac Watson nappe and the Lac Booth klippe. These allochthonous units, characterized by Nd-model ages <1.8 Ga are bound by a magmatically reworked Archean terrane (referred to as the reworked Archean parautochthon) with a Nd-model age range of 1.9-2.6 Ga. Likewise, the perimeter of the reworked Archean parautochthon is truncated by a pristine Archean terrane which exclusively hosts Nd-model ages> 2.6 Ga, indicating that there are three crustal stacking levels in the northern section. Nd-model age mapping was employed in the Mattawa klippe region with the same objectives as in the northern section and additionally to provide constraints on the methodology that is to be used when mapping first-order tectonic boundaries such as the ABT. Ketchum and Davidson (2000) suggested that the ABT trended northward in this region based on the presence of 1.16 Ga coronitic metagabbros which Ketchum (1994) concluded were exclusively confined to the allochthonous polycyclic belt (APB). It was detennined here that although the metagabbros are confined to allochthonous crust, based on Nd-model ages, they are contained within an allochthonous klippe (Mattawa klippe) overlying the reworked Archean parautochthon, that transported the coronitic metagabbros northwestward. Therefore, this klippe represents an erosional remnant ofthe APB but the main ABT is located further south. Nd-model age mapping in the southern region identified three distinct crustal terranes. The Mattawa fault was detennined to be a brittle fault following approximately along a pre-Grenvillian suture. This separates the reworked Archean parautochthon from the Paleoproterozoic parautochthon, which had a Nd-model age range from 1.8-1.9 Ga The Paleoproterozoic parautochthon was found to be truncated by the main body of the APB, containing Nd-model ages < 1.8 Ga. The boundary between the Paleoproterozoic parautochthon and the APB was interpreted as the location of the main ABT. Based on the distnbution of Nd-model ages in the region, four distinct crustal terranes were identified representing two thrusting events. Initially the ABT was overthrust on the parautochthonous belt causing decollement of the reworked Archean parautochthon. The entrainment of the reworked Archean parautochthon under the APB generated a duplex thrust sheet, which resulted in the consequent northwestward thrusting of the reworked Archean parautochthon over the pristine Archean terrane. Finally, the ABT was offset by post-Grenvillian normal faulting associated with Ottawa-Bonnechere graben.
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 | 0,001 |
| 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 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| 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 ».