The B26 Cu-Zn-Ag-Au project, Brouillan volcanic complex, Abitibi greenstone belt, part 1: geological setting and geochronology
Bibliographic record
Abstract
Archean synvolcanic base metal deposits vary greatly in style and metal budget through time and space. This variability is due to contrasting geological and magmatic settings, the influence of which remains a research topic with potential exploration implications. The B26 Cu-Zn-Ag-Au project, located in the Harricana-Turgeon belt of the northern Abitibi greenstone belt, is interpreted as a volcanogenic massive sulphide deposit formed in an evolving calc-alkaline (FII-type) intermediate to felsic centre (Brouillan volcanic complex). The B26 deposit is enriched in Ag and is part of a group of precious metal-enriched Archean volcanogenic massive sulphide deposits that are associated with calc-alkaline volcanic rocks, indicating that such successions are highly prospective. The B26 host succession, informally divided into a lower intermediate member and an upper felsic member, is composed of an andesitic base intercalated with dacitic domes, onto which the felsic member was emplaced. The felsic member comprises three geochemically and texturally distinct rhyolite units that were emplaced as sills, domes, and/or flows with associated relatively voluminous fragmental facies. This felsic succession, dated at 2728 Ma, is coeval both with the host rhyolite of the nearby Selbaie polymetallic deposit and the Brouillan pluton. It is overlain by thin sedimentary strata and cut by andesitic sills and andesitic transposed dykes. This volcanic pile, undergoing extension and containing thick permeable strata, was favourable for the development of a high-temperature hydrothermal system characterized by extensive zones of Cu-rich stringers and sub-seafloor Zn-Ag-(Pb)-rich sulphide lenses in an evolving, possibly shallow-water, active volcanic centre.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".