Intermediate to mafic volcaniclastic units in the peripheral Blake River Group, Abitibi Greenstone Belt, Quebec: origin and implications for volcanogenic massive sulphide exploration
Bibliographic record
Abstract
Three regionally mappable, plagioclase-rich, intermediate to mafic volcaniclastic units from the peripheral parts of the Archean Blake River Group show intriguing similarities, including a lack of an intimate association with lava flows; and a bedded aspect, with thick, coarse beds displaying a typical sequence of internal features, suggesting deposition from high-density mass flows. The bounding facies and the great volume of variably amygdaloidal clasts and plagioclase crystals contained in the deposits supports major submarine explosive eruptions as the source of the bulk of the material. The physical resemblance between the different volcaniclastic units initially suggested a stratigraphic correlation, but preliminary geochemical data argues against this: the D'Alembert tuff consists of basaltic andesite and andesite of transitional to calc-alkaline affinity, whereas the Stadacona unit essentially comprises tholeiitic basalt, with very different profiles on multi-element plots. Any hypothesis involving a megacaldera and a huge underlying magma chamber to explain the origin of these volcaniclastic units would need to justify such chemical differences. The authors favour a simpler scenario in which the D'Alembert tuff and the Stadacona unit were derived from much smaller, geographically and chemically distinct magma chambers. The explosive eruptions could have taken place at different times and no stratigraphic correlation between the volcaniclastic units is necessary. Peripheral areas of the Blake River Group contain more fragmental material than the traditional Noranda camp, and therefore offer exploration potential for large volcanogenic massive sulphide deposits formed in part by subseafloor replacement, which are preferentially hosted in volcaniclastic rocks (e.g. Bouchard-Hébert, LaRonde Penna).
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".