Preliminary Petro-Geochemical Investigation of the Ni–Cu Occurrence of W1 Ultramafic Intrusion (Wapatik) within the Lower Eastmain Greenstone Belt of the Superior Province, Eeyou–Istchee Baie-James, Northern Quebec, Canada
Bibliographic record
Abstract
The Superior Province and its greenstone belts are favourable environments for theemplacement of mafic–ultramafic intrusions prospective for Ni-Cu-(PGE) mineral-ization. However, remote areas of the Superior Province, such as the Eeyou–IstcheeBaie-James region of northern Quebec, remain underexplored. In 2021, Ni-Cu sul-phide mineralization was discovered in a previously unrecognized kilometre-scaleultramafic intrusion, referred to as “W1”, within the Lower Eastmain greenstonebelt (LEGB) of the La Grande subprovince. W1 is a folded, undifferentiated ultra-mafic sill, located on the southern flank of a regional E–W trending anticline,emplaced within the ca. 2752 Ma Kauputauch Formation. This formation corre-sponds to the first volcanic cycle of the LEGB and consists of a succession of vol-canic and volcano-sedimentary rocks that have reached greenschist to amphibolitefacies. The W1 intrusion is emplaced within sulphide-rich supracrustal rocks of theKauputauch Formation and subsequently intruded by late felsic plutons and gab-broic dykes. It is composed mainly of peridotite, with subordinate olivine pyroxeniteand pyroxenite. Small enclaves of pyroxenite are occasionally recognized within peri-dotite. Diffuse crosscutting contacts between peridotite and pyroxenite units suggestthat they were emplaced synchronously. Several styles of Ni-Cu mineralization occurwithin W1: (1) disseminated sulphide within the ultramafic rocks, (2) semi-massiveto massive sulphide at or near the contact with footwall rocks or internally withinthe intrusion, and (3) semi-massive sulphide veinlets within the metasedimentaryrocks stratigraphically below the intrusion. The semi-massive to massive sulphide isthe most common mineralization style and can be found at two locations, albeit withvery different characteristics. A first occurrence occurs within the hinge zone of thedeposit-scale fold and consists of a few horizons (0.1 to 1.15 m) of semi-massivesulphide containing ultramafic and wall rock clasts. Sulphide occurrences are anassemblage of pyrrhotite, pentlandite and chalcopyrite that grade up to 2.68% Ni,1.30% Cu, and 0.09% Co over 3.30 m. The second occurrence occurs on the limbof the fold and exhibits a classic magmatic ore profile showing, from bottom up,massive, semi-massive, net-textured, and disseminated sulphide. It occurs in the mid-dle of the ultramafic body, presumably at a contact between two subunits. The sul-phide assemblage is dominated by pyrrhotite and is relatively depleted in chalcophileelements compared to the first occurrence. Future work will consist of petrographyand whole rock geochemistry of the mineralization and ultramafic rocks of theintrusion and will provide further insight on the mineral potential of Archean ultra-mafic intrusions of Eeyou–Istchee Baie-James.
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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 | 0.002 |
| Science and technology studies | 0.001 | 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) | 0.002 | 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.
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