U-Pb AGES FROM MAFIC ROCKS ASSOCIATED WITH ORTHOMAGMATIC Ni-Cu-Co SULPHIDE MINERALIZATION IN WEST-CENTRAL LABRADOR
Bibliographic record
Abstract
Most orthomagmatic Ni–Cu–Co sulphide mineralization in Labrador is associated with Mesoproterozoic plutonic suites. The best-known examples are at Voisey’s Bay and Pants Lake, where host intrusions are dated between 1332 and 1313 Ma. Magmatic sulphide mineralization in western Labrador is associated with the Michikamau Intrusion, and sheet-like mafic intrusions assigned to the Shabogamo Gabbro. This article presents U–Pb zircon and baddeleyite data that constrain the ages of these intrusions and their contained syngenetic mineralization. Mineralization in the Michikamau Intrusion was dated using a coarse-grained pegmatitic variant of the host leucotroctolite, adjacent to, and gradational with, a sulphide-bearing zone. Single-grain analyses of baddeleyite define an age of 1469 ± 1 Ma, indicating that this is the earliest Mesoproterozoic magmatic sulphide mineralization yet identified in Labrador. The result is consistent with a previous age determination inferred to represent associated contact metamorphism. In the Evening Lake area of the Gagnon terrane, sulphide mineralization was dated using a dioritic variant of the sheet-like gabbroic host intrusion, which gave a zircon age of 1448 ± 2 Ma. This confirms the assignment of the host rocks to the Shabogamo Gabbro, and is the first precise age from these rocks within the autochthonous foreland of the Grenville Province in Labrador. A closely similar zircon age of 1444 ± 4 Ma was previously obtained from gabbro of the sparsely mineralized Mount Fyne intrusion, emplaced within deeper level crystalline rocks of the Molson Lake terrane. The results confirm general correlation of mafic intrusive suites across the boundary between the Gagnon and Molson Lake terranes as high-level and deep-level representatives of a single magmatic suite. Results confirm that magmatic sulphides are hosted by older Mesoproterozoic anorthositic and gabbroic suites as well as their younger counterparts. They also suggest that the Shabogamo Gabbro may have wider potential for magmatic sulphide mineralization. However, age is not the only determining factor that should be used in assessing the potential of individual intrusions. The apparent contrast in prospectivity between the Evening Lake and Mount Fyne intrusions suggests that local geological factors such as the presence of suitable sulphide-bearing country rocks may be an equally significant indicator of mineral potential.
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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 | 0.002 | 0.002 |
| 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".