Sulfides and Noble Metals in Primitive Arc Basalts
Bibliographic record
Abstract
Sulfide globules entrapped in primitive olivine phenocrysts (Mg# 86-92) from arc basalts (Tolbachik volcano, Kamchatka, Russia) preserve the compositions of primary magmatic sulfide melts. The globules have high concentrations (up to 38 mol%) of CuS and NiS that indicates low sulfide supersaturation in magma, when the diffusion fluxes of FeS, NiS and CuS into growing globules are comparable. The phase composition of sulfides depends on the quenching rate during the eruption and varies from homogeneous through intergrowths of MSS and ISS to fully crystallized globules containing FeS, CuFeS 2 , CuFe 2 S 3 , Cu 5 FeS 4 , (Fe,Ni) 9 S 8 and Fe 3 O 4 . Trace elements (PGE, Ag, Te, Au, Pb and Bi) are present in solid solution in sulfide phases and as micron-sized "nuggets" scattered randomly within sulfide matrices or at phase boundaries and outer surfaces of the globules. Concentrations of PGE in sulfides follow a log normal distribution over five orders of magnitude from 0.29 to > 20,000 ppm Au + PGE. Correlations between noble metal abundances suggest diffusive equilibration between sulfide and silicate melts. However some anomalous concentrations suggest entrapment of Au-PGE-rich particles (solid or liquid) from magma. This is further supported by very high Pd of 2% in two sulfide globules, associated with fine Pd particles disseminated in co-trapped silicate melt. Tolbachik sulfide globules have mean composition resembling those of major PGE-sulfide ore deposits (e.g., Norilsk, Sudbury, Platreef and Merensky Reef). The sulfide-silicate immiscibility in the Tolbachik parental melt occurred at ~1220 C, 3 kbar and QFM+ 1.1.
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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) | 0.000 | 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) | 0.005 | 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; 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".