Intensive Variables in Kimberlite Magmas, Lac de Gras, Canada and Implications for Diamond Survival
Bibliographic record
Abstract
Abstract Crystallization temperatures (T) and oxygen fugacities (fO2) of kimberlite magma are estimated from oxides included in olivine phenocrysts from the Leslie, Aaron, Grizzly and Torrie kimberlite pipes in the central Slave Province, Canada. Crystallization temperatures recorded by olivine–chromite pairs at an assumed pressure of 1·0 GPa are 1030–1170°C ± 50°C, with a mean of ∼1080°C. At these temperatures, the fO2 of coexisting olivine and chromite is 2–3 log units less oxidized than the nickel–nickel oxide (NNO) buffer at a silica activity limited by the presence of monticellite. Mass balance of olivine, bulk-rock and liquid compositions in equilibrium with olivine phenocryst rims suggests that these kimberlites represent crystallization from a magma with 11–28 mol % of liquid, 10 mol % of earlier precipitated olivine phenocrysts and 62–79 mol % of mantle xenocryst olivine. The calculated T–fO2 values indicate that diamonds entrained in the Lac de Gras kimberlites were probably transported to the surface within the stability field of graphite but close to the graphite–CO2 boundary.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 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) | 0.002 | 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".