Relative timing and controls on advanced argillic and conventional alteration of the Neoarchean Onaman volcanogenic massive sulfide deposit, Ontario, Canada
Bibliographic record
Abstract
Volcanogenic massive sulfide (VMS) deposits with advanced argillic alteration display characteristics typical of conventional VMS and high-sulfidation epithermal deposits. Unlike conventional VMS deposits, these “hybrid” VMS are interpreted to have formed through a magmatic fluid contribution to an evolved, seawater-dominated, hydrothermal system. The close spatial association of advanced argillic alteration assemblages with more typical chlorite–sericite assemblages in the same VMS deposit has implications for the controls on magmatic versus seawater convective systems that have not been previously addressed in the literature. The Neoarchean Onaman assemblage (ca. 2780–2769 Ma) in northwestern Ontario hosts a conventional base metal VMS system with chlorite–sericite alteration that is overprinted by argillic and advanced argillic alteration, now manifested as a metamorphosed zone of kyanite–chloritoid–calcite–Fe–chlorite, that is associated with a barren, pyritic VMS deposit. The change from typical to advanced argillic alteration occurred during, or immediately following, the deposition of a tonalite clast-bearing heterolithic breccia, which recorded the uplift and subaerial exposure of the larger volcanic edifice. We postulate that the reactivation of synvolcanic structures during uplift, concomitant localized subsidence, and magmatism enhanced cross-stratal permeability and allowed for a direct magmatic volatile input into, or overprint on, an evolved seawater-dominated hydrothermal system. Our results suggest that geodynamic regimes exert a strong local, and possibly regional, control on the style, timing, and fluid characteristics of VMS hydrothermal systems. The association of advanced argillic alteration with barren pyritic massive sulfide also suggests that magmatic volatile input alone is not sufficient to enrich VMS systems in gold. This interpretation is consistent with observations from other magmatic–hydrothermal systems such as porphyry and epithermal deposits.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| 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 | 0.000 |
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".