A Comparative Study of Sulfur Isotope Variations within the Flatreef and Merensky Reef of the Bushveld Complex, South Africa
Notice bibliographique
Résumé
ABSTRACT The Flatreef, a down-dip, sub-horizontal extension of the Platreef, which underlies the Turfspruit and Macalacaskop farms, represents the future of platinum mining in South Africa. The stratigraphic connection between the Platreef, located at the base of the northern limb of the Bushveld Complex, and the Merensky Reef in the western and eastern limbs of the complex, was disputed for many years due to the heterogeneous nature of the Platreef along strike. However, the discovery of the Flatreef led to a new perspective on the Platreef as the former allowed for the study of a magmatic stratigraphy less affected by footwall interaction. Here, we report whole-rock S isotope (δ34S) compositions across the stratigraphic units of the Flatreef and its footwall and hanging wall as intersected by boreholes UMT-276 and UMT-393, as well as stratigraphic units of the Merensky Reef at Two Rivers Platinum mine in the eastern limb. The units of the Flatreef containing platinum group element mineralization, namely the Main Reef and Upper Reef, have δ34S values that overlap with the range recorded for the Merensky Reef in the western and eastern limbs. In UMT-393, Main Reef δ34S values range between 0.2 and 1.5‰ (with the exception of three outliers, 9.7‰, 11.1‰, and 7.9‰), and 0.52‰ and 11.2‰ for two Upper Reef samples. However, in UMT-276, Main Reef δ34S values range between –0.96 and 2.24‰ and 3.19‰ was recorded for an Upper Reef sample. The S isotope compositions recorded for the Merensky Reef pyroxenite at Two Rivers Platinum mine are relatively higher with δ34S values ranging between 1.24 and 4.83‰. The top unit of the Flatreef, which is a transition zone below the Main Zone, as well as the Footwall Cyclic Unit have heavier S isotope compositions with δ34S values ranging between 6 and 17‰ for the former and 0.7 and 18.6‰ for the latter. At Two Rivers Platinum mine, the hanging-wall anorthosite has a δ34S value of 2.9‰ in contrast to the 5.7‰ measured for the footwall anorthosite and 3.27‰ for the footwall feldspathic pyroxenite. The consistent near-mantle S isotope signature and accompanying metal enrichment in the Main Reef of the Flatreef may be explained by extensive interaction of sulfide minerals in a Lower Zone conduit/pre-Platreef staging chamber with large volumes of uncontaminated magma. The δ34S values of the Merensky Reef at Two Rivers Platinum mine are slightly higher compared to that of the Main Reef at Turfspruit and Macalacaskop possibly due to interaction with underlying carbonate rocks.
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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 | 0,000 | 0,000 |
| 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 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 ».