<sup>40</sup> Ar/ <sup>39</sup> Ar and Rb–Sr dating of gold-bearing quartz–breccia mineralization and deformation within the Gordon Lake Region, Northwest Territories, Canada: a tribute to Dr. Nick Culshaw and 30 years on
Bibliographic record
Abstract
Regional and detailed mapping at Gordon Lake has closely outlined the structural timing of a km-scale refold and linked this event to the formation gold-bearing quartz–breccia zones. Early (F 1 ) isoclinal folds, that were refolded (F 2 ) during a secondary (D 2 ) deformation event coeval with peak regional metamorphism, lead to the development of a pervasive (S 2 ) regional cleavage and sub-vertical (L 2 ) stretching lineation. Tightening and increased strain within the east limb of the Gordon Lake refold structure occurred during D 3 along with the development of a localized (S 3 ) crenulation cleavage and an episode of quartz–breccia mineralization. The nearby Spud Lake pluton intruded the region post-peak metamorphism. New in situ Rb–Sr geochronology on white mica from the pluton defined an overdispersed regression date of 2573 ± 17 Ma, which overlaps an existing 40 Ar/ 39 Ar date of 2592 ± 14 Ma and other U–Pb zircon ages for nearby granitic plutons of the Prosperous Suite. Rb–Sr geochronology of biotite from a sample of quartz–breccia mineralization yielded a single population regression at 2480 ± 53 Ma. This date is significantly younger than a previous 40 Ar/ 39 Ar date of 2564 + 14 Ma, perhaps indicating the incorporation of excess 40 Ar available during the mineralization event. The Rb–Sr date from the quartz–breccia is consistent with field relationships that indicate the mineralization post-dates peak metamorphism.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.042 | 0.008 |
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".