Geologic setting, nature, and structural evolution of intrusion-hosted Au-bearing quartz veins at the Longline occurance, Moosehorn Range area, west-central Yukon Territory
Bibliographic record
Abstract
The Longline gold occurrence is located within the Tintina Gold Belt, in the Moosehorn Range area of west-central Yukon Territory. Gold occurs in sheeted, high-grade (-30 g/t), shallowly dipping mesothermal quartz veins hosted within mid-Cretaceous intrusions of the Dawson Range batholith. Felsic to intermediate intrusions in the Moosehorn Range area are probably closely related; they were emplaced at -96-100 Ma, and have similar geochemical and lead isotopic compositions. Geochemistry of the intrusive phases suggests the magmas were mantlederived, subduction-related, and extensively contaminated by continental crust. The goldbearing quartz veins post-date all of these intrusions and are cut by younger mafic dykes. Metallic minerals inside the veins include galena, sphalerite, arsenopyrite, pyrite, boulangerite, tetrahedrite, native gold, and scheelite. The alteration assemblage includes muscovite, sericite, iron carbonate, pyrite, arsenopyrite, minor clay, quartz, and tourmaline. Vein minerals precipitated from moderately saline fluids, containing H₂0-C0₂-CFi₄-NaCl + N₂ , at temperatures of ~260°-300°C, pressure of -1.3 - 1.9 kbar, and depth of 5-7 km, assuming near-lithostatic fluid pressures. Lead isotopic studies indicate the Moosehorn Range area intrusions are not the source of the metals in the veins and the ultimate source remains uncertain. The veins were emplaced between 92 and 93 Ma along NNW-striking, shallowly ENE-dipping brittle reverse fault structures during a WSW-verging contractional event. The veins are 1cm to lm thick, sheeted, lens-shaped, banded, and locally connected by subhorizontal dilational oreshoots, creating a ramp-flat geometry. The long axis of the oreshoots is NNW and slip along the reverse faults was up-dip towards the WSW. Regional structural context for the formation of the veins is unclear. Prominent NNW-trending topographic and magnetic lineaments in the area may be dextral strike-slip faults along which there may be contractional and dilational jogs. Contraction at a jog in the vicinity of the Longline property may have generated the structures that host the veins. If so, dextral strike-slip faults and associated contractional and/or dilational jogs may be an important exploration guide to finding other shallowly dipping auriferous quartz vein systems in the region.
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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 | 0.000 | 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".