Geochemical investigations of high-grade quartz-scheelite veins of the Cantung Mine, Northwest Territories
Bibliographic record
Abstract
High-grade quartz-scheelite veins (up to 3.7 wt.% WO3) in the open pit orebody of the Cantung mine, Tungsten, Northwest Territories occur 300 m vertically above a Cambrian limestone-Cretaceous monzogranite contact along which the E-Zone, a world-class tungsten skarn orebody, is developed. The trend of an 80 m wide vein swarm is roughly parallel to the strike and dip of a near-vertical aplite dyke along the edge of the open pit. Adjacent to these quartz-scheelite veins, dark green alteration selvedges overprint earlier light green skarn alteration. This overprint implies that the high-grade quartz-scheelite veins are not part of the early skarn-forming event but represent a distinct, later event. Oxygen isotope data from vein-hosted quartz-scheelite pairs yield equilibrium depositional temperatures of 430 to 595°C. These temperatures indicate that the high-grade quartz-scheelite veins are related to a deep magmatic hydrothermal system and are likely a distal expression of a protracted skarn-forming event, perhaps related to aplite dyke emplacement. Quartz-scheelite veins did not form in a shallower, cooler, hydrothermal system during uplift. Primary ore fluids in quartz-scheelite veins from the open pit orebody, in skarn-related quartz veins from the E-Zone orebody, and in aplite dykes are grossly similar H2O-CO2-NaCl ± CH4 fluids. However, two distinct end-member fluids have been documented: aplite-related fluids and skarn-related fluids (in quartz veins from the E-Zone orebody). Fluids in high-grade quartz-scheelite veins contain components of both end-member fluids. High-grade quartz-scheelite veins from the open pit orebody share a common structural attitude with aplite dykes. Fluids in veins from the open pit orebody contain an aplite-related fluid end-member even when occurring up to 70 m from the nearest exposed aplite dyke. Thus, quartz-scheelite veins and aplite dykes in the open pit orebody probably have a genetic relationship in addition to their structural relationship. The authors envision a conceptual model for the Cantung hydrothermal system in which ore-grade tungsten deposits formed where fluids emerged from the granite and encountered rocks favourable for skarn development (e.g. cleaner 'ore limestone' versus cherty 'swiss cheese limestone'). Due to the folded geometry of the sedimentary sequence, in other areas along the granite contact, the fluids emerging from the granite encountered strata less favourable to skarn development (i.e. argillite). Where these less favourable units were breached by fracture systems, potential skarn-forming fluids (and aplite dykes) gained access to host rocks more conducive to ore development vertically distal to the granite contact. The presence of magmatic ore fluids distal to intrusions is intriguing and has significant implications for mineral resource assessment 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 | 0.001 | 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".