SOLUBILITY OF Ta IN THE SYSTEM CaCO3 - Ca(OH)2 - NaTaO3 - NaNbO3 F AT 0.1 GPa: IMPLICATIONS FOR THE CRYSTALLIZATION OF PYROCHLORE-GROUP MINERALS IN CARBONATITES
Bibliographic record
Abstract
Experimental data are presented for an evaluation of the solubility of tantalum in the ternary system CaCO 3 – Ca(OH) 2 – NaTaO 3 (or calcite – portlandite – sodium tantalate) over the temperature range 550 to 900°C at 0.1 GPa pressure. Near-liquidus phase relationships are given for the pseudobinary join ([CaCO 3 ] 45 [Ca(OH) 2 ] 55 ) 100– x – (NaTaO 3 ) x , 30 x 3 . The primary crystallization fields of calcite and microlite are separated by an exceptionally steep thermal valley located at about 55 wt.% NaTaO 3 . Quenched liquids contain calcite, portlandite, Na–Ca carbonates and calcium–tantalum oxide. The maximum solubility of tantalum in this system is estimated to be on the order of ~48 wt.% Ta 2 O 5 . At higher NaTaO 3 contents, microlite (isostructural with pyrochlore) crystallizes. In contrast, our previous work has demonstrated that lueshite, a perovskite-structured compound, crystallizes in the system CaCO 3 – Ca(OH) 2 – NaNbO 3 at high NaNbO 3 contents. The addition of 1.75 wt.% F to theTa system studied depresses the liquidus by >150°C, and tantalum solubility exceeds 61 wt.% Ta 2 O 5 . In experiments in the system CaCO 3 – Ca(OH) 2 – NaTaO 3 – NaNbO 3 , we found primary niobian microlite to crystallize at high temperature, and tantalian pyrochlore at lower temperature.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".