Superimposed Porphyry Systems in the Dawson Range, Yukon
Bibliographic record
Abstract
ABSTRACT Superimposed porphyry systems are a subset of telescoped porphyry deposits, whereby significantly younger ore zones overprint older, nongenetically related systems. Recognition of superimposed features in porphyry systems is important for determining and assessing their prospectivity. The Mount Nansen gold corridor in the southern Dawson Range gold belt of Yukon, Canada, contains porphyry prospects and epithermal deposits with enigmatic genetic models. Geologic, petrologic, temporal (U-Pb zircon, Re-Os molybdenite), and geochemical (whole-rock) studies are used to demonstrate the presence of superimposed porphyry systems in this district. The arc-related episodic magmatism of the Mount Nansen gold corridor has been classified into four intrusive suites: (1) Late Triassic Minto, (2) mid-Cretaceous Whitehorse, (3) Late Cretaceous Casino (eLKc; 80–72 Ma), and (4) Late Cretaceous Prospector Mountain (lLKp; 72–65 Ma). Geochemical fingerprinting of these suites indicates intermediate to evolved, calc-alkaline compositions with a common lower crust melt source. The eLKc and lLKp suites lack an Eu anomaly and show increasing amounts of light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion over time. These features suggest that garnet was stable in the melt source and oxidized magmas were generated in these Late Cretaceous suites. The mildly alkaline lLKp and associated Carmacks Group shoshonitic basalts reflect localized extension in an overall compressive arc setting in the Mount Nansen gold corridor, hence a setting conducive for Au-rich porphyry and epithermal systems. The ca. 79 to 72 Ma Casino suite is commonly interpreted as the causative magmatic event for most well-endowed porphyry deposits (76 to 74 Ma in age) in the Dawson Range gold belt. However, our detailed study of the Klaza setting shows that at this locality, intermediate-sulfidation epithermal veins are a distal expression of a Prospector Mountain-age (ca. 71 Ma) porphyry system, which overprints two Casino-age porphyry systems (ca. 77 and 80 Ma). The Mount Nansen gold corridor thus hosts at least two spatially and temporally overprinting Late Cretaceous magmatic-hydrothermal systems in the Dawson Range gold belt. Importantly, recognition of this feature at other porphyry deposit settings in the Dawson Range gold belt (e.g., Freegold Mountain district) is critical as it provides the potential for metal (Cu-Au-Mo)-enriched hypogene ore shells.
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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 | 0.001 |
| 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".