Application of Molybdenum and Thallium Isotopes as Indicators of Paleoredox Conditions and Genesis of Hyper-Enriched Black Shale (HEBS) Deposits, Peel River, Yukon
Bibliographic record
Abstract
Hyper-enriched black shale (HEBS) deposits, such as those hosted in Devonian black shales of northern Yukon, are a globally significant source of a variety of economically important metals, particularly nickel, copper, zinc and platinum group elements (PGE). The Yukon HEBS occurs as a thin (<10 cm) but laterally extensive (1000s km) stratiform and stratabound mineralized horizon that is enriched in a number of metals, significantly, Ni-Mo-Zn-PGE. The genesis of such deposits and the ambient paleoenvironment in which they formed are the subject of vigorous debate. Two genetic models, seafloor hydrothermal alteration and seawater scavenging have the most traction. These models invoke euxinic conditions for the formation and preservation of semi-massive sulfides. Non-traditional isotopes, particularly molybdenum and thallium, are robust paleoredox indicators, especially where bulk geochemical paleoredox indicators exhibit ambiguities. Systematic sampling and Mo and Tl isotopic analysis of a 200 m stratigraphic section through the Yukon HEBS mineralization and the footwall and hanging-wall strata at the Peel River north and south bank showings give δ98Mo -1.24 to -0.53‰ and ε205Tl -8.1 to -5.2 for the mineralization, and 0.05 to 0.60‰ and -4.8 to -4.4 for the unmineralized strata, respectively. These values preclude a hydrothermal origin, but, together with rare earth elements (REE) and several bulk geochemical redox indicators, indicate that the mineralization formed from seawater in a quiescent, euxinic basinal paleoenvironment.
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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 | 0.000 | 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) | 0.000 | 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".