Convergent margin Ni-Cu-PGE-Cr ore systems: temporal and magmatic evolution
Bibliographic record
Abstract
Ultramafic-mafic intrusions at convergent margins contain some of the world's significant Ni-Cu-PGE sulphide deposits and are becoming an increasingly important exploration target. This class of intrusions is well-represented in the accreted arc terranes of the northern Cordillera, particularly the Alaskan-type subclass. In this report, we describe current research on three Alaskan-type intrusions in British Columbia that are variably endowed in magmatic Ni-Cu-PGE mineralization. The goal of this project is to determine the timing of mineralization in relation to the temporal and magmatic evolution of the intrusion and to develop new mineral deposit models as guides for exploration. U-Pb and 40Ar/39Ar geochronological results for the Turnagain intrusion indicate multi-stage assembly of a composite body in the Early Jurassic (ca. 189-185 Ma) during initial accretion of arc terranes to the ancient North American continental margin. Ni(-Co) and Cu-PGE sulphide mineralization is partitioned within separate sub-intrusions that were emplaced during active accretion. A newly investigated zone of Cu-Pd-Pt sulphide mineralization in the Tulameen intrusion bears a strong resemblance to certain 'reef-style' deposits in layered intrusions. Preliminary geochronology results indicate emplacement of the Tulameen intrusive suite in the latest Triassic (ca. 204-206 Ma), coincident with the most prolific Cu-Au porphyry epoch in British Columbia. Investigation of magmatic sulphide occurrences at the Polaris Alaskan-type intrusion was initiated last summer and samples collected during the field season are currently being processed and examined.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".