Fahlore as a petrogenetic indicator: Keno Hill Ag-Pb-Zn District, Yukon, Canada
Bibliographic record
Abstract
Abstract Fahlores [~(Cu,Ag)10(Zn,Fe)2Sb4S13] from the Keno Hill mining district, central Yukon, Canada record virtually the entire petrogenetic history of a Cretaceous hydrothermal system extending over 40 km outward from the Mayo Lake granitic pluton. These fahlores are an essential constituent of polymetallic sulphide veins developed in a graphitic Mississippian quartzite, where they occur in association with sphalerite, pyrargyrite, galena and siderite. Fahlores exhibit pronounced east-west zoning in average Ag/(Ag+Cu) and Zn/(Zn+Fe) values, with these simultaneously increasing and decreasing from east to west over 20 km of hydrothermal activity. These zonations are coupled with average Ag/(Ag+Cu) and Zn/(Zn+Fe) values in fahlore roughly paralleling the 300°C isotherm for fahlores in equilibrium with pyrargyrite, miargyrite and sphalerite in the simple system Ag2S-Cu2S-ZnS-FeS-Sb2S3. Early high-Ag, high-Zn fahlores from the eastern and western mines have Ag/(Ag+Cu) and Zn/(Zn+Fe) values requiring temperatures ≥400°C, in agreement with temperatures established from the As-content of arsenopyrite coexisting with pyrite, pyrrhotite and sphalerite. Ag/(Ag+Cu) and Zn/(Zn + Fe) values in later, main-stage fahlores are consistent with the 250–310°C range of temperatures established for boiling of Keno Hill fluids. Finally, Ag- and Fe-rich fahlores were produced by retrograde Fe-Zn exchange with sphalerite or crystallized from late-stage epithermal fluids which produced polybasite, stephanite, acanthite and wire silver. One such fahlore exhibits unmixing into high-Ag and low-Ag varieties. This is the first reported miscibility gap for freibergite fahlores and confirms the earlier prediction of such gaps.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.000 |
| 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".