Petrology, geochemistry, and isotopic composition of magmatic \nsulphide occurrences in the Montagnais Sill Complex, northern \nQuébec, Canada
Bibliographic record
Abstract
The Labrador Trough of northern Québec is a site of ongoing exploration for magmatic Ni-Cu-PGE (platinum-group element) sulphide deposits. The region is considered favourable for such deposits because it is host to voluminous mafic-ultramafic intrusive and extrusive rocks of the Montagnais Sill Complex (MSC) that are located proximal to trans-crustal faults and sulphidebearing country rocks. In addition, the MSC is the easternmost segment of the ∼ 1.88 Ga Circum-Superior large igneous province, which hosts world-class magmatic Ni-Cu-PGE deposits in the Thompson and Cape Smith belts. However, only a number of sub-economic magmatic sulphide occurrences have been identified in the MSC. In the present study, the newly discovered Idefix PGE-Cu and Huckleberry Cu-Ni-(PGE) prospects are used as case studies to evaluate ore-forming processes operating in the Labrador Trough as well as the prospectivity of the region regarding magmatic sulphide deposits. The Idefix PGE-Cu prospect represents a > 400-m-thick stack of aphyric gabbro sills (∼ 8- 14 wt.% MgO, ∼ 1-8 Cr/V) that contain disseminated sulphides (0.2-0.4 g/t Pd+Pt+Au, 0.1- 0.5% Cu and < 0.1% Ni over a thickness of 16-34 m) in its centre and globular sulphides at its base. Both sulphidic horizons are spatially associated with stratiform gabbroic pegmatites, all of which can be traced intermittently for ∼ 7 km along strike. Primary silicate, oxide, and sulphide minerals have undergone moderate to extensive alteration that prevented mineral chemical analysis. It was determined from whole-rock and PGE geochemistry that the sills share a common transitional-MORB source and that the extracted magma underwent significant fractionation before emplacement in the upper crust. Chalophile metals and sulphur show good positive interelement correlations, suggesting that the distribution of metals is primarily controlled by sulphides (pyrrhotite > chalcopyrite > pentlandite ≫ sulpharsenides) and partially controlled by tellurides and electrum. Whole-rock compositions provided no clear evidence for crustal contamination (e.g., La/SmN < 1, Th/YbN < 1, and S/Sewr < 4,000), yet the sulphides, and particularly globular sulphides, have
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".