Interaction Of Rare-Metal Minerals With Hydrothermal Fluids: Evidence From Quartz–Epidote Metasomatites Of The Haldzan Buragtag Massif, Mongolian Altai
Bibliographic record
Abstract
A quartz–epidote metasomatite from the Haldzan Buragtag massif, Mongolian Altai, provides evidence for the low-temperature hydrothermal alteration of rare-metal minerals. In what was essentially a continuous sequence of events during a complex evolutionary history, a peralkaline granitic pegmatite was metasomatized by hydrothermal fluids related to the associated intrusions. Minerals in the pegmatite, including fergusonite-(Y), chevkinite-(Ce), and members of the epidote supergroup, were recrystallized and texturally coarsened at temperatures in the range 318–446 °C. These phases were then altered by lower-temperature fluids (156–160 °C), with replacement of chevkinite-(Ce) by titanite–rutile–cerite-(Ce)–REE-carbonate assemblages and fergusonite-(Y) by complex hingganite–cerite–thorite assemblages. Late-stage veining included cerite-(Ce), fergusonite-(Y), and REE-carbonates. Generally, the light rare-earth elements (LREE) were replaced by Y, heavy rare-earth elements (HREE), and Ca as alteration proceeded. Mineral assemblages are interpreted to show that the hydrous fluids were acidic and oxidizing, contained significant amounts of CO2, but were poor in F and Cl. The fluids may ultimately have been derived from basaltic magmas emplaced after formation of the pegmatite.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".