Geochemical constraints on magmatic and metallogenic processes: Iskut River Formation, volcanogenic massive sulfide-hosting basalts, NW British Columbia, Canada
Bibliographic record
Abstract
Volcanic rocks of the Jurassic Iskut River Formation (IRF) in northwestern British Columbia (Canada) host several volcanogenic massive sulfide (VMS) deposits, including the exceptionally high-grade Eskay Creek Ag–Au–Cu–Pb–Zn deposit. The IRF comprises voluminous pillow basalt (>90%), minor rhyolite, and sedimentary rock of late Early to early Middle Jurassic age, filling a series of sub-basins along a 300 by 50 km north-trending belt. Two geochemically distinct types of tholeiitic basalts interfinger; both resemble back-arc basin basalts formed from the melting of asthenospheric and sub-arc mantle sources. Group 2 basalts are more enriched in light rare-earth elements, Ba, K, Sr, Th, and U, and have lower positive εNd values than group 1 basalts (+3.2 to +6.3 versus +6.9 to +8.4, respectively). The compositional differences between group 1 and group 2 basalts are interpreted to result from crustal contamination in group 2. Group 1 basalts are most common in the southern part of the IRF belt where they are closely associated with the Eskay Creek, Bonanza, and Hidden Creek (Anyox) VMS deposits. Group 2 basalts are most abundant in the northern half of the belt and are not associated with exploited mineral deposits. The lack of crustal contamination in group 1 basalts indicates that they formed from rapidly ascending magma in an advanced rift setting and were associated with high heat flow that drove hydrothermal circulation. Group 1 and group 2 basalts are reliably discriminated by Ta/Th <2.5 in the former and >2.5 in the latter. This geochemical criteria can therefore be used as an exploration tool to identify VMS permissive sub-basins and (or) stratigraphy in the IRF.
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 | 0.003 | 0.003 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.002 | 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".