PGE-Rich Ni-Cu Sulfide Mineralization in the Flin Flon Greenstone Belt, Manitoba, Canada: Implications for Hydrothermal Remobilization of Platinum Group Elements in Basic-Ultrabasic Sequences
Bibliographic record
Abstract
The Flin Flon greenstone belt is best known for its world-class volcanogenic massive sulfide deposits. However, the recent discovery of the McBratney platinum group element (PGE)-Au occurrence and other PGE occurrences has drawn attention to the potential for Ni-Cu-PGE (Au) deposits in this belt. The McBratney occurrence contains some of the highest PGE and Au grades found in this type of deposit in North America (up to 207 g/t Pd, 34 g/t Pt, 2.6 g/t Rh, and 75 g/t Au). It is hosted in chlorite-actinolite and chlorite schists of the Bear Lake magmatic unit in the Bear Lake block of the Flin Flon greenstone belt. The metamorphosed host rocks are komatiitic and tholeiitic in composition. The mineralization is hydrothermal and postdates the regional, retrograde metamorphic event. It occurs as sulfide-rich veins and surrounding disseminated zones controlled by faults, as well as isolated disseminated zones within chlorite-actinolite and chlorite schists. Platinum group minerals (PGM) and gold are spatially and temporally associated with pyrrhotite, chalcopyrite, carbonate, second generation chlorite, chamosite and, locally, stilpnomelane. In the disseminated zones, these phases replace the metamorphic actinolite-chlorite assemblage in both types of host rocks. Locally the veins are layered with pyrrhotite-rich zones and chalcopyrite-rich zones. The PGM include, in order of abundance, Te-rich sudburyite, borovskite, sperrylite, sudburyite, an unknown Pd-Te-Sb mineral, temagamite, and merenskyite, which occur mainly as inclusions in the sulfides. Minor amounts of PGE also occur within chlorite, carbonate, and stilpnomelane, and Au-Ag alloy is observed locally included in Fe sulfides in association with sphalerite. The mantle-normalized metal distribution shows that the McBratney mineralization is enriched in Bi, As, Au, Pd, Cu, Pt, Rh, Os, Ru, Zn, Re, and Ag; the mineralization is both enriched and depleted in Ir and Cr, and it is depleted in Ni in all analyzed samples when compared with typical komatiitic magmatic ore. The mineral assemblage suggests that the hydrothermal fluids were reduced (pyrrhotite-pyrite stable), neutral to alkaline, and CO 2 bearing (carbonate-chlorite stable). Chlorite geothemometry indicates that the hydrothermal assemblage formed at temperatures ranging from 250° to 350°C. Under these conditions, PGE may have been transported mainly as bisulfide complexes and their precipitation likely occurred due to reactions of the hydrothermal fluids with the Fe-rich host rocks, which led to the formation of Fe sulfides, reduction of the activity of the bisulfide, and formation of PGM. Palladium precipitated mainly as tellurides and antimonides; however, Pt formed an arsenide. The abundant As, Te, and Sb may have been crucial in forming high-grade PGE ore. Sulfur isotope data indicate that magmatic rocks or fluids were likely the sources of sulfur, which may include the metamorphosed basic-ultrabasic sequence, hidden magmatic Ni-Cu sulfide mineralization, or fluids derived directly from postmetamorphic magmatic rocks.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 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".