COLLINSITE IN HYDROTHERMAL ASSEMBLAGES RELATED TO CARBONATITES IN THE KOVDOR COMPLEX, NORTHWESTERN RUSSIA
Bibliographic record
Abstract
Several generations of collinsite were formed during the hydrothermal alteration of phoscorite and dolomite carbonatite in the Kovdor alkaline-ultramafic complex, northwestern Russia. The collinsite at this locality shows isomorphic substitution of Sr fo r Ca at the A crystallographic site , which is atypical both for this species and for the entire fairfieldite group. The Sr content reaches 0.74 atoms per formula unit and shows an inverse correlation with Ca. Sr is found to account for no more than 37% of the total occupancy of the A site, a proportion that fits the Lewis acidity of interstitial cations, a value of 0.25 valence units (assuming a disordered distribution of Sr), which in turn matches the Lewis basicity of the structural unit in collinsite, the chain [Mg(PO4)2(H2O)2]. The collinsite-bearing assemblages were formed by juvenile hydrothermal solutions derived from phoscorites and carbonatites that had been cooling in a tectonically active environment. Textural evidence and strontium isotopic character istics show that the assemblages were superimposed upon the host rocks after the cataclasis of the dolomite carbonatite and selective leaching of its primary minerals. The Sr isotopic composition of collinsite and the associated hydrothermal phosphate s shows no contribution from any crustal component. Being confined to faults, the orthomagmatic hydrothermal solutions migrated upward and were not mixed with groundwater or crustal fluids in tectonic channels prior to deposition of the collinsite-bearing assemblages. The active fluid–rock interaction below 270 °C under wide variations in pH–Eh parameters, f(O2), f(S2), and relatively low f(CO2) did not homogenize the isotopic composition of Sr between the solutions and the affected carbonate rock.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".