ABSTRACT: Geologic Summary of the Sweet Grass Hills, Liberty and Toole Counties, Montana
Notice bibliographique
Résumé
ABSTRACT The Sweet Grass Hills are a northwest-trending group of five intrusive-cored buttes near the Canadian border north of Shelby, Montana. West Butte and Middle Butte are cored predominantly by diorite. East Butte has a core mainly of syenite and syenite porphyry. Grassy Butte was formed by the intrusion of a plug of felsite breccia. Haystack Butte is cored by a plug of hornblende vogesite. The domal structure of the buttes is the result of the vertical force produced during the emplacement of the igneous rocks. A complicated pattern of northwest- and northeast-striking faults has disrupted the general domal structure of the buttes. The faults were probably controlled by Precambrian basement structures and show evidence of repeated movement. Sedimentary rocks have been intruded and metamorphosed to varying degrees by the intrusive rocks. The oldest rocks exposed in the Sweet Grass Hills are limestones of the Mississippian Madison Group, which are unconformably overlain by the Jurassic Ellis Group. The Upper Jurassic Morrison Formation is absent. The Cretaceous Kootenai, Blackleaf, and Marias River formations occur in a roughly concentric pattern around the buttes. Younger Cretaceous rocks of the Telegraph Creek Formation, Eagle Sandstone, Claggett Shale, and Judith River Formation occur in the lower slopes around the buttes. In general, the best exposures and most complete stratigraphic section of sedimentary rocks occur at East Butte. The Sweet Grass Hills are important to the economy of the surrounding region. Gold has been produced near the Gold Butte town-site on the west side of Middle Butte and lode mineralization containing low-grade gold is known to occur in East, Middle, and West Buttes. Gold produced at Middle Butte is from a placer deposit in pediment gravel and alluvial gravel, both of which are derived from lode deposits about 1/2 mile (0.8 km) to the east. Gold mineralization in lode deposits in all three of the Buttes is associated with contacts between igneous rocks and sedimentary rocks. At East Butte the gold is probably controlled by the contacts between syenite and Madison Limestone. Fluorite is associated with this mineralization. Mineralization in Middle and West Buttes is associated with the contact of diorite with sedimentary rocks mainly of the Colorado Group. Diamond exploration is being conducted just across the border in Canada and potential for diamond occurrences does exist in the Sweet Grass Hills area on the Montana side of the border. No favorable host rocks for diamonds are known in the Sweet Grass Hills, but the composition and thickness of the Archean basement, the likely presence of thick lithosphere in the area, and regional relations suggest diamond occurrences are possible beneath the cover of glacial till. Anticlinal and domal structures cored by intrusive rocks in the plains surrounding the Sweet Grass Hills have produced significant volumes of oil and gas.
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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 | 0,002 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,011 | 0,001 |
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 ».