Magmatic processes associated with the Voisey's Bay Ni-Cu-Co sulphide deposit, Labrador, Canada
Bibliographic record
Abstract
The Voisey's Bay deposit is considered anomalous within the terms of World-Class magmatic Ni sulphide deposits as it is hosted by low-olivine, low-forsterite troctolites within an anorthosite complex - a combination not previously considered a viable prospect for economic Ni-sulphide mineralisation. <br><br>The accepted model for generation of a sulphide magma at Voisey's Bay has been contamination of the troctolite parental magma at mid-crustal levels by the sulphidic and graphitic Tasiuyak gneiss. Trace element and mineralogical data presented here suggest that sulphide immiscibility is the result of contamination of the Voisey's Bay magmas by Nain gneiss, probably at the base of the crust. <br><br>Olivine geochemistry suggests that the source of the Ni at Voisey's Bay is a now departed high-Mg# melt with forsterite >F0<sub>80</sub>. Trace element evidence implies that this melt was plume-like and derived from 7-8 percent partial melting at gamet/spinel facies. The melting temperature was ~1530°C, the pressure was ~3.25 GPa, the ƒ0<sub>2</sub> ~QFM. <br><br>Pb isotope, trace element, olivine and sulphide geochemical data imply that there was a sulphide liquid present before the parental magmas encountered the Tasiuyak gneiss. Although the Tasiuyak gneiss has contaminated the Voisey's Bay silicate magmas, the extent of contamination is small and coincidental. The Voisey's Bay intrusion sulphides and silicates exhibit different Pb isotope ratios, this disequilibrium is explained in terms of immiscibility, density contrasts and contamination models. <br><br>Data presented in this thesis allow the relative timing of the main events in the forming of the Voisey's Bay deposit to be constrained and for a new model of deposit genesis to be proposed. This new model provides new criteria for exploring within anorthosite complexes for another Voisey's Bay- type magmatic Ni-sulphide deposit.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.003 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.007 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.009 | 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".