Mineral Chemistry of (Pt,Pd)-Bismuthotelluride Minerals In the Platreef At Zwartfontein, Akanani Project, Northern Bushveld Complex, South Africa
Bibliographic record
Abstract
The (Pt,Pd)-bismuthotelluride minerals at the Akanani prospect show substantial substitution of Te and Bi. Individual grains are often markedly heterogeneous with concentrations of Te and Bi which vary by up to 26 wt.%. They occur as single phase crystals or form composite grains with other platinum-group minerals, and are predominantly associated with ( i.e. , are in direct contact with) primary and secondary silicate minerals, base-metal sulfides, and magnetite. The Pt-bismuthotelluride minerals are markedly associated with ( i.e. , tends to occur as composite grains with) Pd-bismuthotelluride minerals, isoferroplatinum, and sperrylite. The Pd-bismuthotelluride minerals are markedly associated with Pt-bismuthotelluride minerals, altaite, hollingworthite, plumbopalladinite, PdSbSn alloy, and sperrylite. The Pt-bismuthotelluride minerals are characterized by high ratios of Te/Bi and form a trend of solid solution from moncheite (PtTe2) towards maslovite (PtTeBi). A few analyses plot close to, or on, the composition of maslovite. The Pd-bismuthotelluride minerals are characterized by a lower ratio of Te/Bi than the Pt-bismuthotelluride minerals. They form a trend of solid solution along the join kotulskite (PdTe)–sobolevskite (PdBi), without merenskyite (PdTe2). There is very limited solid solution of Pt and Pd between the Pt-bismuthotelluride minerals (<5.7 wt.% Pd) and the Pd-bismuthotelluride minerals (<3.3 wt.% Pt), with only four analyses of michenerite (three grains) characterized by elevated levels of Pd (10.3 to 17.1 wt.%). In view of the strong spatial association between the Pt- and Pd-bismuthotelluride minerals at Akanani it is considered likely that the latter were originally in solid solution in a precursor Pd-rich Pt-bismuthotelluride host at temperatures of up to 1150 °C, from which they then exsolved during cooling. Further exsolution of Te- or Bi-rich domains in individual Pt- and Pd-bismuthotelluride crystals occurred during late cooling at substantially lower temperatures, and resulted in the observed compositional ranges of moncheite–maslovite and kotulskite–sobolevskite.
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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 | 0.000 |
| 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".