A Barrovian Overprint Superimposed on Partly Preserved High-Pressure Metamorphic Rocks: Pressure–Temperature–Time Evolution in the Ordovician Corner Brook Collisional Complex (Western Newfoundland, Canada)
Notice bibliographique
Résumé
Abstract The Corner Brook Collisional Complex in western Newfoundland represents an exhumed part of the partially subducted Humber margin of Laurentia metamorphosed at medium grade and intermediate to high-pressure conditions during collision with outboard arcs. It is interpreted as part of an extruded collisional wedge and consists mainly of metapelitic rocks and minor basement orthogneiss. Its subdivision into different metamorphic zones is supported by calculated PT pseudosections that display a continuous increase in metamorphic grade at intermediate-pressure conditions. The PT paths indicate an evolution at five stages: (I) Burial of peri-Laurentian continental crust after initiation of subduction at the end of the early Ordovician (~470 Ma) during obduction of oceanic crust, which initiated nucleation of garnet at 500°C to 550°C, 6.2 to 9.3 kbar. (II) Maximum, probably Taconic, burial at 520°C to 610°C, 8.2 to 11.7 kbar of one group of samples was followed (III) by extrusion and exhumation with simultaneous thermal relaxation. (IV) Subsequent imbrication within the complex during the Salinic orogeny was accompanied by extensive fluid flow due to prograde dehydration of a second group of rocks at mid-crustal levels during burial. A final stage of thermal relaxation (560–650°C, 6.9–9.2 kbar) created a Barrovian zonation. The ensuing observed peak temperature mineral assemblages are pervasive and only relicts of a former high-pressure stage are preserved locally. Interrelated PT paths of opposing direction can be related to mid-crustal stacking. (V) Finally, post-peak metamorphic folding and faulting of the Barrovian zones created an elongated metamorphic dome transected by brittle thrusts. U–Th–Pbtot dating of monazite inclusions in garnet of one sample yields an age of 438 ± 14 Ma interpreted as the time of garnet growth near peak temperature conditions at intermediate pressures. Also, two white-mica-bearing assemblages were dated by Rb/Sr mineral isochrones at 429 ± 6 Ma and 440 ± 6 Ma, respectively. The U–Th–Pbtot monazite and older Rb/Sr age combined with existing U/Pb ages of rutile suggest the presence of an older age population around 438 ± 4 Ma. Published 40Ar/39Ar ages of white mica and amphibole combined with the younger Rb/Sr age represent a younger age population around 427 ± 4 Ma. Both groups are related to successive separate phases of deformation and recrystallization near and/or after the thermal peak. Extensive fluid influx notably influenced the evolution of various segments of the complex but varied strongly between metamorphic zones.
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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 | 0,001 | 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 | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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 ».