Ophiolite-related associations of platinum-group minerals at Rudnaya, western Sayans and Miass, southern Urals, Russia
Bibliographic record
Abstract
ABSTRACT We describe similar assemblages of minerals found in two placers in Russia, both probably derived from an ophiolitic source. The first is located along the River Rudnaya in the western Sayan province, Krasnoyarskiy kray, and the second pertains to the Miass placer zone, Chelyabinsk oblast, in the southern Urals. The platinum-group element (PGE) mineralization in both cases is mostly (at least 80%) represented by alloy minerals in the system Ru–Os–Ir, in the order of occurrence osmium, ruthenium and iridium. The remainder consists of Pt–Fe alloys and species of PGE sulfides, arsenides, sulfarsenides, etc. The associated olivine and amphiboles are supermagnesian, and the chromian spinel has a high Cr# value. The observed enrichment in Ru, typical of an ophiolitic source, may be due to high-temperature hydrothermal equilibration and mobilization in the ophiolite, as is the enrichment in Mg and Cr. Low-temperature replacement of the alloys led to the development of laurite, sulfoarsenides and arsenides. Some placer grains in both suites reveal unusual phases of sulfo-arsenoantimonides of Ir–Rh, e.g. the unnamed species (Rh,Ir)SbS and (Cu,Ni) 1+ x (Ir,Rh) 1– x Sb, where x = 0.2, and rhodian tolovkite, (Ir,Rh)SbS. Two series of natural solid-solutions appear to occur in the tolovkite-type phases. Among the oddities in the Rudnaya suite are globules of micrometric PGE sulfides, crystallites of platinum-group minerals, amphibole, and chalcopyrite bearing skeletal micrometric monosulfide-like compounds (Cu,Pt,Rh)S and (Pd,Cu)S 1– x . Pockets of fluxed evolved melt seem to have persisted well below the solidus of the host Pt 3 Fe-type alloy.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.013 | 0.001 |
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; both teacher heads agree on what is shown here.
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".