Carbon Isotope Composition of Graphite in Mantle Eclogites
Bibliographic record
Abstract
The carbon isotopic composition of diamond is reasonably well-known from measurements on hundreds of diamonds of known paragenesis.With very few exceptions, 5'^C values of peridotite-suite diamonds are in the restricted range -2 to -9%<?pdb, whereas 5*^C for eclogitic diamonds ranges from approximately +2 to -34%opdb (e.g., Sobolev et al., 1979;Deines, 1980;Harris, 1987).In contrast to this large data set, few isotopic data have been published for either eclogitic or peridotitic mantle-derived graphite.Values of 5^^C for primary graphites from peridotite xenoliths (-4.8 to -10.04%o; Kropotova and Fedorenko, 1970;Pearson et al., 1990; Schulze and Valley, in press) are similar to those from peridotitic diamonds.Existing carbon isotope data for graphite in mantle eclogites from Mir (Kropotova and Fedorenko, 1970), Roberts Victor (Deines et al., 1987), and Orapa (Deines et al., 1991) are, with one exception, in the "typical mantle range" (-3.98 to -8.7%opdb)-Graphite from a Schaffer, Wyoming kyanite eclogite (Schulze and Valley, in press) is unusually light, with 5*^C = -14.31%o.An additional anomalous graphite analysis (5^^C of -20.3%o) was reported by Deines et al. (1991) for a corundum-garnet-spinel assemblage of uncertain affinity, also from Orapa.To enlarge the data base for mantle-derived graphites, we present carbon isotope data for graphites from 23 eclogite xenoliths, from the Bellsbank and Jagersfontein kimberlites in South Africa and the Orapa and Letlhakane kimberlites in Botswana.
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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 | 0.000 |
| 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".