Compositional variation and genesis of pyrochlore, belkovite and baotite from the Sevattur carbonatite complex, India
Bibliographic record
Abstract
Abstract Pyrochlore-group minerals are common in the Neoproterozoic Sevattur carbonatite complex. This complex is composed of dolomite-, calcite-, banded- and blue carbonatite together with pyroxenite, albitite and diverse syenites. This work reports the paragenetic-textural types and compositional variation of pyrochlore hosted by dolomite carbonatite, banded carbonatite and albitite together with that of alteration assemblages containing belkovite and baotite. On the basis of composition, five different types of pyrochlore are recognised and termed Pcl-I through to Pcl-V. The Pb-rich Pcl-I are present exclusively as inclusions in U-rich Pcl-IIa in dolomite carbonatite. The alteration assemblages of Pb-poor Pcl-IIb + Ba-rich or Ba–Si- rich Pcl-IV + belkovite (dolomite carbonatite) and Si-rich Pcl-V + baotite (banded carbonatite) formed after Pcl-IIa differ in these carbonatites. The albitite hosts extremely U-Ti-rich Pcl-III, mantled by Ba-rich potassium feldspar. In common with the banded carbonatite, Pcl-V is formed by alteration of Pcl-III where this mantle is partially, or completely broken. The Ba-Si-enrichment of Pcl-IV and Pcl-V together with the ubiquitous presence of baryte in all Sevattur lithologies suggests late-stage interaction with a Ba-Si-rich acidic hydrothermal fluid. This fluid was responsible for leaching silica from the associated silicates and produced Pcl-V in the silicate-rich lithologies of the banded carbonatite and albitite. The absence of Pcl-V in dolomite carbonatite is a consequence of the low modal abundance of silicates. The complex compositional diversity and lithology specific pyrochlore alteration assemblages suggest that all pyrochlore (Pcl-I to Pcl-IV) were formed initially in an unknown source and transported subsequently in their respective hosts as altered antecrysts.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.004 | 0.002 |
| Science and technology studies | 0.000 | 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".