Sedimentary processes, provenance, and tectonic control on fluvial sandstone geochemistry during Superior craton stabilization
Notice bibliographique
Résumé
ABSTRACT The Neoarchean marked an important turning point in the evolution of Earth when cratonization processes resulted in progressive amalgamation of relatively small crustal blocks into larger and thicker continental masses, which now comprise the ancient core of our continents. Although evidence of cratonization is preserved in the ancient continental cores, the conditions under which this geodynamic process operated and the nature of the involved crustal blocks are far from resolved. In the Superior craton, deep-crustal fault systems developed during the terminal stage of Neoarchean cratonization, as indicated by the cratonwide growth of relatively small, narrow, syn-to-late tectonic (ca. 2680–2670 Ma) sedimentary basins. The terrigenous debris eroded from the uplifted tectono-magmatic source regions was deposited as polymictic conglomerate and sand successions in fluvial-dominated basins. The composition of the sedimentary rocks in these unique basins, therefore, offers a unique record of crustal sources and depositional settings, with implications for the geodynamic processes that formed the world’s largest preserved craton. Here, we compare the geochemical compositions of sandstone samples from six sedimentary basins across the Abitibi greenstone belt and relate them to their mode of deposition, prevailing provenance, and geodynamic setting during crustal growth and craton stabilization. The sandstones represent first-cycle sediment that is poorly sorted and compositionally very immature, with variable Al2O3/TiO2 ratios and index of chemical variability values >1 (average of 1.36), reflecting a large proportion of framework silicate grains. The sandstones display chemical index of alteration values between 45 and 64 (average of 53), indicating that the detritus was eroded from source regions that experienced a very low degree of chemical weathering. This likely reflects a high-relief and active tectonic setting that could facilitate rapid erosion and uplift with a short transit time of the detritus from source to deposition. Multi-element variation diagrams and rare earth element patterns reveal that the lithological control on sandstone composition was dominated by older (>2695 Ma) pretectonic tonalite-trondhjemite-granodiorite and greenstone belt rocks. The sandstone units display large variations in the proportions of felsic, mafic, and ultramafic end-member contributions as a consequence of provenance variability. However, an average sandstone composition of ~65% felsic, ~30% mafic, and ~5% komatiite was observed across the basins. This observation is in agreement with recent models that predict the composition of the Neoarchean emerged continental crust for North America and supports the presence of a felsic-dominated Archean crust. The high proportion of felsic rocks in the upper crust requires continuous influx of H2O into the mantle and is best explained by subduction-related processes. In such a scenario, the detritus of the fluvial sandstones is best described as being controlled by uplifted and accreted continental arcs mainly composed of tonalite-trondhjemite-granodiorite and greenstone belt rocks.
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) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,026 | 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 ».