Tholeiitic to calc-alkaline cyclic volcanism in the Roy Group, Chibougamau area, Abitibi Greenstone Belt — revised stratigraphy and implications for VHMS explorationGeological Survey of Canada Contribution 20100254. Ministère des Ressources naturelles et de la Faune Contribution 8439-2010-2011-17.
Bibliographic record
Abstract
The Roy Group in the Chibougamau area of the Abitibi subprovince, Southeastern Superior craton, Quebec, exemplifies Archean volcanic evolution. The Roy Group formed in two volcanic cycles, with voluminous basal mafic tholeiitic volcanic rocks being capped by a thin succession of calc-alkaline felsic volcanic rocks, banded iron formations, and cherts that represent regional stratigraphic markers. The Gilman Formation is thought to represent the mafic base of the 2nd Roy Group volcanic cycle. Our new mapping reveals that the Gilman Formation (North of the Lac Doré Layered intrusive complex) can be subdivided into a tholeiitic lower part (David member), a calc-alkaline extrusive sequence (Allard member), and a tholeiitic, more mafic upper part (Bruneau Formation, newly defined here). New U–Pb zircon ages on Allard member tuffs (2726.6 ± 0.7 Ma) are within error of those obtained from rhyolites of the Waconichi Formation (2728.2–2728.7 Ma), which underlies the Gilman Formation. These ages, along with geochemical and lithological similarities, imply that the Allard member belongs to the Waconichi Formation and that the David member occupies the same stratigraphic position as the Obatogamau Formation. The upper part of the former Gilman Formation is reassigned to the new Bruneau Formation. A thin transitional calc-alkaline basalt unit at the base of the Allard member is geochemically similar to basalts occurring at the top of the Lemoine member of the Waconichi Formation near the Lemoine mine, suggesting that the Allard member is slightly younger than the Lemoine member, and that its base (also associated with iron formation, breccia, and chert) represents a regional stratigraphic break favourable for volcanogenic-hosted massive sulphide (VHMS) exploration.
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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 | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".