SCANDIUM MINERALOGY: PRETULITE WITH SCANDIAN ZIRCON AND XENOTIME-(Y) WITHIN AN APATITE-RICH OOLITIC IRONSTONE FROM SAINT-AUBIN-DES-CHATEAUX, ARMORICAN MASSIF, FRANCE
Bibliographic record
Abstract
The scandium phosphate pretulite has been identified with scandian zircon and xenotime-(Y) in an apatite-rich oolitic Ordovician ironstone at Saint-Aubin-des-Châteaux, Armorican Massif, France. Pseudo-octahedral crystals of pretulite, up to 400 m across, have grown epitactically on detrital zircon. They reveal complex zoning due to incorporation of Y and HREE, as well as to an extended solid-solution toward the zircon end-member. Characteristic compositions in the pretulite ‐ xenotime-(Y) ‐ zircon system are: Prl0.973Xnt0.020Zrn0.007, Prl0.907Xnt0.088Zrn0.005, Prl0.873Xnt0.042Zrn0.085, Prl0.718Xnt0.024Zrn0.258 and Prl0.453Xnt0.042Zrn0.505. A single-crystal X-ray refinement of the structure in space group I41/amd (R = 0.0389) gives a 6.5870(9), c 5.809(1) A, for the formula (Sc0.904Y0.032HREE0.016Zr0.048)(P0.952Si0.048)O4. The Raman spectrum is presented. Detrital zircon shows phosphate-rich metamict zones containing HREE and Sc (up to 3.2 wt.% Sc2O3). Analytical and crystallographic data suggest a complete solid-solution between zircon and pretulite. Xenotime-(Y), also epitactic on zircon, shows distinct stages of crystallization, with a decrease in Y together with an enrichment in the lighter REE and Sc (up to 0.7 wt.% Sc2O3). The scandium minerals at Saint-Aubin reflect the evolution of the iron ore, from sedimentation to diagenesis and metamorphism, followed by multistage hydrothermal leaching and recrystallization. Despite the high concentration of Fe in the environment, this quite unique occurrence of Sc minerals illustrates the high capacity of the phosphate ion to extract scandium and precipitate it as a specific phase, at relatively low-temperature conditions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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 teacher head, 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".