Till geochemical signatures of volcanogenic massive sulphide deposits: an overview of Canadian examples
Bibliographic record
Abstract
Volcanogenic massive sulphide (VMS) deposits are an important source of Cu, Pb, Zn and Ag in Canada. These deposits formed on the paleo-seafloor in volcanic or volcano-sedimentary rocks. On the glaciated landscape of Canada, the bulk composition of till (so-called ‘till geochemistry’) is an important exploration method for VMS deposits. Herein we provide an overview of the 50-plus year history of the application of till geochemical methods to VMS exploration in Canada, and summarize best practices, including appropriate size fractions of till to analyse, analytical techniques and indicator and pathfinder elements. Till geochemical methods are now well-developed and used widely, most commonly employing the <0.063 mm till fraction and an extensive suite of VMS indicator elements Cu, Pb, Zn, Au, and Ag, as well as pathfinder elements Ag, Au As, Bi, Cd, Ga, Ge, Hg, In, Sb, Se, Sn, Tl. In order to detect the clastic glacial dispersal signal down-ice of a VMS deposit, unoxidized to weakly oxidized till should be collected and analysed, and not B-horizon soil. Case studies and examples of glacial dispersal patterns associated with known VMS mineralization in major mining camps and deposits across Canada are highlighted.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.010 | 0.017 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".