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
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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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Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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