A new geological environment for rodingite formation: Metasomatism in kimberlite volcanoes
Bibliographic record
Abstract
Rodingite is a calc-silicate rock containing garnet, diopside, and chlorite that develop via metasomatic replacement of ultramafic to felsic rocks. Rodingites are found in ophiolites subjected to low-grade metamorphism or hydrothermal serpentinization of the surrounding ultramafic rocks. Here we report a previously unrecognized volcanic environment for rodingite formation. Rodingites can result from skarn-like reactions between kimberlite and xenoliths of silicate country rocks.We studied hypabyssal and pyroclastic kimberlites from Renard and Gahcho Kue clusters (Canada) and Orapa (RSA). The kimberlites entrain 20-90 vol.% of granitoid and gneiss (Renard 65, Gahcho Kue) and basalt (Orapa) xenoliths collectively called silicate country rocks. Skarn-like reactions triggered by gradients in the chemical potentials of Si, Al, Ca, and Mg across the xenolith–kimberlite contacts produce concentric reaction zones within the xenoliths and a reaction halo in the surrounding contaminated kimberlite. The original mineralogy of the unreacted xenoliths is replaced by prehnite, diopside, pectolite, wollastonite, serpentine, garnet, calcic hydrosilicates (hydrogarnet, xonotlite, amphiboles). In the kimberlite halo, diopside and phlogopite form, carbonate is leached out, olivine is completely serpentinized. Rodingites develop by moderate degrees of reaction, and are replaced with monomineral serpentine and chlorite if metasomatism advances further.Petrographic evidence for post-emplacement, metasomatic development of rodingite assemblages in kimberlite matches the Perple_X phase equilibria calculations that model the formation of the reactive mineralogy in the subsolidus, at T
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 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".