Identifying externally derived sulfur in conduit-type Cu–platinum-group element deposits: The importance of multiple sulfur isotope studies
Bibliographic record
Abstract
Abstract The Marathon conduit-type Cu–platinum-group element (PGE) deposit occurs within the Proterozoic Coldwell alkaline complex, Ontario, Canada, and comprises three zones of mineralization that occur at varying distances from the contact with Archean country rocks. Multiple sulfur isotope studies (δ34S, Δ33S, Δ36S) of sulfides from the Marathon deposit show that Δ33S and Δ36S measurements, as well as the relationship between them, are critical in demonstrating crustal S contamination. This is particularly significant for magmatic Cu-PGE deposits in contact with Archean country rocks where the δ34S of sulfides are within the range of typical mantle values (0‰ ± 2‰), as is the case at the Marathon deposit. Although the δ34S values of sulfides from the Marathon deposit did not reflect any evidence of crustal S assimilation, the Δ33S range (−0.91‰ to 0.00‰), and a negative correlation between Δ33S and Δ36S, indicate that S was derived from both the mantle and Archean supracrustal rocks. Given that the country rocks contain insignificant amounts of sulfide, crustal S assimilation must have occurred at depth, prior to magma emplacement. The magnitude of the Δ33S anomaly decreases with increasing distance from the basal contact, suggesting either that S contamination was greatest in the mineralized zone that occurred in close proximity to the contact or that crustal S signatures have been diluted in the mineralized zones further from the contact.
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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 | 0.001 | 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) | 0.001 | 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".