COMPOSITION AND PARAGENESIS OF Na-, Nb- AND Zr-BEARING TITANITE FROM KHIBINA, RUSSIA, AND CRYSTAL-STRUCTURE DATA FOR SYNTHETIC ANALOGUES
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Bibliographic record
Abstract
We describe titanite with unusually high contents of Na, Nb, and Zr from a hydrothermal natrolite-rich vein cutting kalsilite‐ nepheline syenite at Mount Rasvumchorr, Khibina peralkaline complex, in the Kola Alkaline Province, Russia. This titanite is associated with astrophyllite, ceriobetafite, yttrobetafite, henrymeyerite, and banalsite. We recognize four generations of titanite: nearly stoichiometric titanite-I, titanite-II, containing up to 16.4 wt.% Nb2O5 (0.25 apfu Nb) and 3.2% Na2O (0.21 apfu Na), titanite-III, with up to 9% ZrO2 (0.15 apfu Zr) and zoned from 12.4 to 2.2% Nb2O5, and (Nb‐Zr)-poor titanite-IV, with up to 3.6% Al2O3 and 2.2% Fe2O3. In titanite-II, substitution of Nb at the octahedral site is accompanied by Na at the seven-fold site and, probably, by (F,OH) ‐ and vacancies. A compositional analogue of titanite-III, and synthetic titanite containing 0.25 apfu Zr, similar to the most Zr-rich titanite known, have been prepared by standard ceramic techniques, and their crystal structure determined by Rietveld refinement of powder X-ray-diffraction patterns. The synthetic variants doped with Zr, or with Zr, Na, and Nb, adopt space group A2/a, and consist of distorted YO7 polyhedra, XO6 octahedra, and SiO4 tetrahedra. The (Ca0.85Na0.15) (Ti0.70Zr0.15Nb0.15)OSiO4 analogue of natural titanite from the Rasvumchorr zeolite vein contains the least-distorted coordination polyhedra. The polyhedra in Ca(Ti0.75Zr0.25)OSiO4 are moderately distorted, and the most strongly distorted polyhedra are those in the CaTiOSiO4 end-member.
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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 | 0.000 |
| 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) | 0.000 | 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 it