Minor elements in sphalerite and their implications for metallogenesis of carbonate-hosted zinc-lead deposits of the Yukon Territory and adjacent district of Mackenzie
Bibliographic record
Abstract
Minor element concentrations in sphalerite from the newly discovered carbonate-hosted zinc-lead deposits in the Yukon Territory and adjacent District of Mackenzie have been determined to define the metallogeny of this remote region of the Canadian cordillera. Concentrations of silver, cadmium, cobalt, copper, iron, manganese, nickel, lead, and mercury in sphalerite were analyzed in 166 specimens from 48 deposits; an additional 13 elements were investigated at a qualitative level. Minor element data defines two ages of regional metallogeny; different mineralizing processes also might be represented by these two events. Sphalerite in the northern cordillera is generally enriched in copper, lead, and mercury, and depleted in iron, relative to other districts containing similar zinc-lead deposits. Iron contents vary sympathetically with darkness of colour in sphalerite. Minor element variations within single hand specimens, and analytical variations, are both insignificant relative to between-specimen variations, as revealed by analyses of variance. Minor element variations within single deposits are small relative to between-deposit variations; therefore, each deposit is characterized by the minor element assemblage of the sphalerite it hosts. Regionally, sphalerite occurrences in carbonate host rocks (dominantly dolomites) occurs as breccia matrix, vein, and fracture fillings. Two major age groups of host rocks, Proterozoic to Lower Cambrian, and Middle Ordovician to Devonian, are separated by an Upper Cambrian to Middle Ordovician unit that is bounded by unconformities and is relatively barren of mineral occurrences. Linear regression analysis of minor element results indicates distinctly different trends for each age group. Probability graph analysis of all minor element contents define bimodal distributions consisting of relatively 'enriched' and 'depleted' populations for most elements. Geographic distributions of sphalerite 'enriched' in minor elements correlate consistently with geographic distributions of Proterozoic and Lower Cambrian host rocks. Sphalerite 'depleted' in minor elements occurs dominantly in Ordovician to Devonian host rocks. A single period of sphalerite deposition is inadequate to explain the observed minor element patterns. Two distinct minor element populations correlating in geographic distribution with two separate age groups of host rocks indicate that at least two independant metallogenic events led to the sphalerite mineralization. A major shale basin, likely dewatering to produce metal-rich brines, is associated only with the Ordovician to Devonian hosts, whereas major unconformities and paleophysiographic elements suggestive of karstic environments are associated with the Proterozoic and Lower Cambrian hosts. A regional interpretation suggests that these different features might be responsible for the different minor element concentrations outlined. Therefore, a model of two metallogenic events, one during Middle to Late Cambrian, and another during Late Devonian or later, is proposed to explain the spatial and temporal relations between minor element populations and host age distributions of sphalerite deposits in carbonate rocks of the northern cordillera.
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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 | 0.001 |
| 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".