Platinum-Group Elements in the Merensky and J-M Reefs: A Review of Recent Studies
Bibliographic record
Abstract
Abstract The Merensky Reef of the Bushveld Complex (South Africa) and the J-M Reef of the Stillwater Complex (U.S.A.) are two layers enriched in platinum-group elements (PGE). In the last few years, several multidisciplinary studies were carried out on samples from these reefs. This includes: 3-D analysis by X-ray computed tomography, in-situ minerals (base-metal sulphide, chromite and primary silicate) or fluid inclusions analysis using laser-ablation ICP-MS, and detailed analysis of the platinum-group minerals (PGM). According to the results of these studies, in both reefs, the PGE are found either in solid-solution in the base-metal sulphides (BMS) or as PGM closely associated with the BMS. No PGE are present in the silicate or oxide lattices. Initially, the PGE were collected by a BMS sulphide liquid that interacted with silicate magma fertile in PGE. Then, the sulphide liquid may have percolated downward along vertical dilatancies formed during the compaction of the cumulate pile and may have stopped where the permeability is too low to allow it to further migrate. The PGE and base-metals were then redistributed either at a local scale (e.g. exsolution of the PGM from the BMS during cooling or partial desulphurization) or at a larger scale as observed in the J-M Reef. In this case, the Pd and to a lesser extent Pt may have been leached (possibly from the footwall) and then reprecipitated at the level of the reef by fluids (either liquid or vapour) during alteration and/or metamorphic events.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".