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
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".