The metamorphosed Neoarchean epithermal Vent prospect, Ontario, Canada
Bibliographic record
Abstract
Epithermal precious metal deposits are uncommon within the Archean rock record, as are detailed descriptions of their associated features and modes of formation. The Vent prospect is a Neoarchean Au–Ag occurrence within the Eastern Wabigoon Subprovince of the Superior Province in Ontario. It is hosted by aphyric, and quartz ± feldspar-porphyritic aphanitic dacitic flows that show remnants of spine-like structures within blocky flow top breccia facies that lack visible hyaloclastite, consistent with subaerial emplacement. Numerous phreatic breccia dikes containing rounded, heterolithic, fragments in a fine rock flour and locally altered matrix intrude the dacitic host rocks, supporting a subaerial setting. Discordant replacement and stringer Au- and Ag-bearing pyrite mineralization is associated with a decimeter-scale, zoned, discordant sequence of metamorphic associations consisting of a) quartz-pyrite; b) kyanite-quartz; c) muscovite-kyanite; and d) muscovite. The geochemical characteristics of these metamorphic associations reflect intense pre-metamorphic acidic alteration. These lithofacies, alteration characteristics, and mineralization styles are consistent with a subaerial volcanic edifice altered by acidic hydrothermal fluids, which periodically brecciated the edifice. We propose that the features that characterize the Vent prospect are consistent with those of Phanerozoic epithermal systems. New U–Pb zircon geochronology of the host dacites indicate formation at ca. 2720 Ma, suggesting that the Vent prospect may represent one of the oldest identified epithermal deposits preserved in the ancient rock record. The recognition of epithermal mineralization in Archean greenstone belts underlain by Mesoarchean crust, such as those of the Eastern Wabigoon, opens up the possibility of potential for gold and silver in other underexplored Archean greenstone belts.
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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 | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.008 | 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".