Potassic Magmas Derived from Metasomatized Lithospheric Mantle: Nomenclature and Relevance to Exploration for Diamond-Bearing Rocks
Notice bibliographique
Résumé
Abstract Kimberlites, orangeites and lamproites are rocks derived by the differentiation and crystallization of genetically diverse mantle-derived magmas Currently, nomenclatural distinctions between these rock types are made on the basis of mineralogical-genetic classifications and not simple modal classification schemes The principle followed in such classification schemes is that the groundmass minerals reflect the fundamental characteristics of the melt from which they crystallized Classification of most of these rocks cannot be made using bulk rock geochemistry as many contain significant and variable amounts of xenocrystal and xenolith mateual It is now well-known that kimberlites are mineralogically and geochemically-distinct from orangeites and lamproites and are probably derived from depleted asthenosphenc mantle sources In contrast, isotopic and experimental petrological data indicate clearly that orangeites, lamproites and other potassic rocks are piobably derived from ancient veined metasomatized (enriched) lithospheric mantle Petrological studies have shown that each lamproite province has unique mineralogical and geochemical characteristics These differences result from the differing metasomatic histories of the source rocks within individual cratons and accreted mobile belts Orangeites are considered to represent the expression of potassic magmatism in the Kaapvaal craton and to have similar sources and origins to lamproites The unique cratonic metasomatic history, perhaps coupled with distinct asthenospheric contributions as the impetus for magma genesis, of each potassic province explains why it is difficult to classify some potassic rocks occurring in the Sao Francisco, Aldan and Dharwar cratons as lamproites, orangeites or kamafugites As the magmas from which these rocks crystallized are the unique expression of potassic magmatism in a particular craton they cannot, by definition, be classified according to schemes devised for potassic magmas in other provinces Inter-provincial similarities arise because of the common physicochemical character of the metasomatic process in the lithospheuc mantle The differences reflect variations in the ages and modes of the metasomatic veins coupled with differing degrees of partial melting and/or asthenosphenc contributions to the magmas Any given craton can contain both kimberlites and potassic rocks Rocks in each potassic province could in theory be given its own terminology, which taken to an extreme could lead to a proliferation of cratonic type-locality names Alternatively, all of these diverse magmas might be collectively termed the metasomatized lithospheric mantle magma group (or MLM magmas) The mineralogical-genetic approach to classification implies that none of the MLM magmas are transitional to kimberlite magmas and that use of the portmanteau term “kimberlite clan rocks” for diverse diamondiferous rocks of different genesis is inappropriate for both scientific and economic purposes The diamond potential of each province of potassic rocks must assessed independently as this will also reflect the unique geological history of the parental lithospheric mantle Correct classification of potentially diamondiferous rocks is essential as this has implications with respect to exploration for, and evaluation of, particular intrusions using heavy mineral indicator suites and/or geophysical methods
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 | 0,001 | 0,001 |
| 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 | 0,001 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| 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 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 ».