Are there Colombian-type emeralds in Canada's Northern Cordillera? Insights from regional silt geochemistry, and the genesis of emerald at Lened, NWT
Notice bibliographique
Résumé
The unusual black shale hosted emerald deposits of Colombia are an important source of the finest quality emeralds. The majority of world emerald deposits are related to granite pegmatites and metamorphic environments, however Colombian-type emerald is amagmatic and is associated with sedimentary-hydrothermal brines of largely evaporitic origin where the key emerald-forming elements are remobilized from black shale during regional compressional tectonism. The valuable gem quality mineralization of Colombian emerald deposits is so far unique, however the basic geological conditions that led to mineralization may not be as unusual. Similar black shale basins hosting evaporites are found worldwide, and could be prospective for Colombian-type emerald mineralization. Canada’s Selwyn Basin and periphery is one similar setting with the distinction of hosting two interesting beryl showings: the Mountain River Beryl (a variation of the Colombian beryl model) and the Lened emerald showing (in which black shale provided vanadium as an emerald chromophore). This thesis presents the results of applying Colombian-type emerald exploration criteria to Selwyn Basin stream sediment geochemistry data, in addition to clarifying the origin of emerald at the Lened showing located within the Selwyn Basin. The unusual black shale hosted emerald deposits of Colombia are an important source of the finest quality emeralds. The majority of world emerald deposits are related to granite pegmatites and metamorphic environments, however Colombian-type emerald is amagmatic and is associated with sedimentary-hydrothermal brines of largely evaporitic origin where the key emerald-forming elements are remobilized from black shale during regional compressional tectonism. The valuable gem quality mineralization of Colombian emerald deposits is so far unique, however the basic geological conditions that led to mineralization may not be as unusual. Similar black shale basins hosting evaporites are found worldwide, and could be prospective for Colombian-type emerald mineralization. Canada’s Selwyn Basin and periphery is one similar setting with the distinction of hosting two interesting beryl showings: the Mountain River Beryl (a variation of the Colombian beryl model) and the Lened emerald showing (in which black shale provided vanadium as an emerald chromophore). This thesis presents the results of applying Colombian-type emerald exploration criteria to Selwyn Basin stream sediment geochemistry data, in addition to clarifying the origin of emerald at the Lened showing located within the Selwyn Basin. We identified several prospective areas in Selwyn basin for further Colombian-type emerald exploration based on Na, K, Be, Cr/V, and rare earth element values, however there are important caveats regarding analytical techniques and the regional nature of silt sampling. We found that Lened is a unique skarn-hosted hydrothermal emerald occurrence (~100 Ma) in which Be was provided by a nearby granite pluton of similar age. The chromophore V was provided by local black shale/mudstone.
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 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,002 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,002 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 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 ».