Reconnaissance thallium isotope study of zinc-lead SEDEX mineralization and host rocks in the Howard's Pass district, Selwyn Basin, Yukon: potential application to paleoredox determinations and fingerprinting of mineralization
Bibliographic record
Abstract
The commonly accepted genetic model for sedimentary exhalative (SEDEX) lead-zinc deposits requires a marine basin with anoxic (no oxygen) and euxinic (free H2S) conditions, in order to provide sulphur to bond with the metals. Recent work on the largest SEDEX district in Canada, the Howard's Pass district, Selwyn Basin, Yukon, has cast doubt on the universality of this model, as the water column may have been suboxic during mineralization. Paleoredox indicators based on bulk geochemical compositions can be contradictory or equivocal. Developments in non-traditional metal stable isotope analysis have shown the potential of certain isotope systems (e.g. molybdenum, uranium, thallium) as paleoredox indicators. We have conducted a bulk geochemical and thallium isotopic traverse through a mineralized intersection (and immediate stratigraphic footwall and hanging wall) from the Anniv East vent-distal SEDEX deposit, Howard's Pass district. The epsilon-205Tl values range from -7.5 to -4.0 for unmineralized samples and -3.6 to -2.6 for mineralized ones. There is good general agreement between certain redox sensitive elements, venerable redox indicators and epsilon-205Tl for the unmineralized host rocks (reflecting suboxic or oxic conditions for the most negative values). Thus, the application of thallium isotopes as a redox indicator in seafloor hydrothermal deposits in sedimentary (or volcano-sedimentary) settings shows great promise. The heaviest values are for mineralized samples, likely reflecting contributions of isotopically heavy thallium from the mineralizing fluids. Preliminary data indicate that thallium isotopes as a redox indicator in mineralized samples is untenable, but it has the potential to fingerprint sulphides precipitated by various processes.
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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 | 0.000 | 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".