The Itabirites of the Quádrilátero Ferrífero and Related High-Grade Iron Ore Deposits: An Overview
Pourquoi ce travail est dans la base
Une base qui oublie comment elle a trouvé un travail ne peut pas être vérifiée. Voici les voies qui ont admis celui-ci.
Notice bibliographique
Résumé
Abstract The Quadrilátero Ferrífero district, located on the southern portion of the San Francisco craton in Minas Gerais, Brazil, comprises Archean greenstone terranes of the Nova Lima Supergroup and the Paleoproterozoic cratonic cover sequences of the Minas Supergroup that consist of quartzites, metaconglomerates, phyllites, dolomites, and banded iron formations. The Minas Supergroup was affected by two orogenic events—the Paleoproterozoic Transamazonian-Mineiro (2.1–2.0 Ga) orogeny and the Neoproterozoic to Early Paleozoic Brasiliano-Araçuaí (0.65–0.50 Ga) orogeny, resulting in complex deformation and metamorphic grades that increase from greenschist facies in the West to amphibolite facies in the East. Metamorphosed iron formations, referred to as itabirites, are found in three compositionally distinct lithofacies, namely quartz itabirite, dolomitic itabirite, and amphibolitic itabirite; these lithofacies are host to a large number of economically important high-grade iron ore deposits that give rise to the name Quadrilátero Ferrífero, or "Iron Quadrangle." High-grade iron ores replace itabirites in tectonically favorable, low-strain sites. faults acted as conduits while large fold hinges were sinks for mineralizing fluids. Hard and fine-grained hematite and/or magnetite orebodies are in the western low-strain domain of the Quadrilátero Ferrífero. Subsequent deformation led to recrystallization and development of distinctly schistose high-grade hematite ores characteristic of the eastern high-strain domain. A combination of hypogene and geologically recent supergene processes is thus invoked to explain the formation of the high-grade iron ores of the Quadrilátero Ferrífero. Three stages of hypogene ore formation are distinguished. The first two of these stages took place early during the Transamazonian orogeny (2.1–2.0 Ga) and are well preserved in the western low-strain domain. During the first stage metamorphic fluids leached SiO2 and carbonates and mobilized iron, which resulted in the formation of massive magnetite bodies, Fe oxide veins, and Fe-rich itabirite bodies; during the second stage, low-temperature, low-salinity fluids caused oxidation of magnetite and Fe-rich dolomite to hematite. The resulting ore is porous to massive and has a granoblastic fabric. The third and final hypogene stage of ore formation is related to thrusts of uncertain age (Transamazonian or Brasiliano orogeny), which dominate the tectonic structure of the eastern high-strain domain of the Quadrilátero Ferrífero. Crystallization of tabular hematite and large platy specularite crystals that overprint the preexisting granular fabric in the presence of high-salinity hydrothermal fluids are characteristic of this stage. During the Neogene, supergene residual enrichment processes gave rise to the formation of soft to friable hematite orebodies. The larger soft orebodies that surround some smaller hard high-grade orebodies are typically associated with dolomitic itabirite. Together, both ore types comprise the giant high-grade iron deposits typical for the Quadrilátero Ferrífero, resulting from the superposition of both hypogene and supergene processes. Pure supergene deposits are considerably smaller and do not extend to deeper levels below the erosion surface.
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.
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 | 0,001 | 0,001 |
| 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 découle