Temporal Separation of W and Sn Mineralization by Temperature-Controlled Incongruent Melting of a Single Protolith: Evidence from the Wangxianling Area, Nanling Region, South China
Notice bibliographique
Résumé
Abstract Tungsten and Sn display similar behavior during magmatic processes and are commonly associated spatially and genetically with highly evolved granites. Nonetheless, they typically form separate deposits, even if their associated granites have the same protolith. This separation may be due to the fractionation of the metals at the magmatic-hydrothermal transition or their differential mobility during partial melting of the metasedimentary protolith. If this separation occurred at the magmatic-hydrothermal transition, the ages of the W and Sn deposits would be very similar, whereas if it occurred during partial melting, the deposits are likely to have different ages because of the concentration of the metals in different magma batches and, in extreme cases, during different magmatic events. New age data from the Wangxianling ore field in the western part of the world-class Nanling W-Sn metallogenic province demonstrate that the W and Sn mineralization took place at different times. The W mineralization (219.5 ± 3.4 Ma) is related to Triassic granites (224.9–217.8 Ma), whereas the Sn mineralization is related to granites of Late Jurassic age (154.7 ± 1.1 Ma). This difference in ages rules out fractionation at the magmatic-hydrothermal transition as an explanation for the spatial separation of the W and Sn deposits and implies that the separation was due to differences in the mobility of W and Sn during partial melting. Both suites of granite originated from the partial melting of the same metasedimentary rocks, and both are reduced and highly evolved. The W granites, however, have a lower zircon saturation temperature (~750°C) than the Sn granites (~800°C), which indicates that the magma forming the W granites was mainly the product of muscovite-dehydration melting, whereas that forming the Sn granites was largely the result of biotite-dehydration melting. The different melting paths indicate that W released during muscovite breakdown dissolved in the magma, whereas Sn was sequestered by restite biotite. At the higher melting temperature, the residual W and Sn, released during the subsequent breakdown of biotite, dissolved in the magma. Thus, the magma that generated at low temperature was enriched in W, leading to subsequent W mineralization, whereas the magma that generated at high temperature was enriched in Sn and produced an Sn-mineralized granite. The whole-rock Sr-Nd isotope data for the Triassic W granites plot in the compositional field of the regional basement rocks and are consistent with partial melting of an orogenically thickened crust by internal heating in a collisional setting. In contrast, the Sr-Nd isotope data for the Late Jurassic Sn(-W) granites are displaced toward a mantle composition, likely reflecting contributions from mantle-derived material. Given the emplacement of many of the Late Jurassic Sn(-W) granites close to the Chenzhou-Linwu fault, we propose that this structure was the focus of decompression melting of the mantle and the injection of mantle-derived melts into the crust during the Late Jurassic, which supplied the additional heat for the melting at higher temperature needed to generate magmas enriched in Sn. This model, which is based on differences in the behavior of Sn and W during crustal melting, is potentially applicable to other Sn-W metallogenic provinces where Sn and W deposits are temporally separated.
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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 | 0,001 |
| 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 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 ».