Hydrothermal rare earth element (REE)-enrichment in an iron-oxide-apatite (IOA)-type deposit at Kwyjibo, Québec, Canada: A fluid inclusion and stable isotope study
Notice bibliographique
Résumé
Rare earth elements (REE), which include the lanthanide series, yttrium and scandium, are considered to be strategic resources for the development of modern society because of their unique properties, which makes them essential for the global energy transition. Iron-oxide-apatite-type deposits are potentially important sources of REE, which are exemplified by the Kwyjibo deposit (Québec, Canada) that hosts measured/indicated resources of 6.92 million tons, grading 2.72 % total rare earth oxides, of which 33 % are heavy REE. The deposit comprises three en echelon zones of seven mineralized showings within the Canatiche Complex of the northeastern Grenville Province, of which the Josette horizon is the largest and the richest in REE. This horizon has been subdivided into an upper disseminated zone, a central massive zone, and a lower laminated zone. The current study focuses on the central massive zone, where the REE have been concentrated by hydrothermal processes, and aims to unravel the physical and chemical controls of the REE mineralization. Rare earth elements were initially carried by a magmatic magnetite-fluorapatite ore hosted within leucogranite. Hydrothermal processes remobilized the REE from the fluorapatite to britholite, followed by a calcic-ferric alteration forming andradite, hastingsite, hedenbergite, titanite and biotite, and a REE re-mineralization forming ferriallanite-Ce and yttrium-rich andradite. The δ13C and δ18O values of calcite, which is coeval with the mineralization, range from -4.61 to -7.6 ‰ and from +8.86 to + 17.32 ‰, respectively. These values and the low concentration of Mg (and Fe) in fluid inclusions suggest the REE re-mineralizing fluid originated from a magmatic source of felsic affinity. Microthermometric measurements were conducted on four distinct types of fluid inclusions in the afore¬¬¬mentioned minerals. These are a NaCl-CaCl2-CaSO4-H2O (±CO2) (NaCl-CaCl2) fluid, a NaCl-KCl-H2O (NaCl)-dominated fluid, a NaCl-CO2-H2O (CO2-NaCl bearing) fluid and a CaCl2-NaCl-H2O (CaCl2)-dominated fluid. The NaCl-CaCl2 fluid, which has moderate salinity (18 to 24 wt.% NaCl eq.) and is weakly acidic (pH values of 5.2 to 5.6), is interpreted to represent the REE remobilization and the calcic ferric alteration. The occurrence of the CO2-NaCl bearing and CaCl2-dominated fluids reflects the separation of immiscible aqueous-carbonic and aqueous fluids in response to the decompression during the waning stages of the Rigolet Phase of the Grenville Orogeny. The heavy and light REE remobilization was facilitated by the transport of the REE as sulfate complexes. Deposition of the hydrothermally remobilized REE as britholite was made possible by a coupled substitution of REE3+ for Ca2+ and Si4+ for P5+ in the fluorapatite, which was driven by the high REE and silica activity. These REE subsequently underwent a second stage of hydrothermal remobilization, again as sulfate complexes, and were deposited as ferriallanite-Ce (light REE) and yttrium-rich andradite (heavy REE). A model is presented for the Kwyjibo IOA-type REE deposit in which the REE were initially concentrated in the fluorapatite of massive magnetite-apatite rocks that accumulated in response to fractional crystallization (and gravity settling) of an A-type granitic magma emplaced during a period of extension towards the end of the Shawinigan Orogeny at ~1150 Ma. Two stages of magmatic hydrothermal activity during the Rigolet phase of the Grenville Orogeny at ~980 Ma led to the leaching of the REE from the magmatic fluorapatite as aqueous sulfate complexes and their concentration to economically exploitable levels, first as britholite and subsequently as light-REE-rich ferriallanite-Ce and heavy-REE enriched andradite
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Prédiction machine sur la base complète
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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 | 0,001 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 ».