THE ROLE OF ARSENIC-RICH MELTS AND MINERAL PHASES IN THE DEVELOPMENT OF HIGH-GRADE Pt-Pd MINERALIZATION WITHIN KOMATIITE-ASSOCIATED MAGMATIC Ni-Cu SULFIDE HORIZONS AT DUNDONALD BEACH SOUTH, ABITIBI SUBPROVINCE, ONTARIO, CANADA
Bibliographic record
Abstract
At the Dundonald Beach South Ni-Cu occurrence in the western Abitibi subprovince, Ontario, Canada, komatiite-hosted magmatic sulfide mineralization (pentlandite-dominated; 0.5–7 ppm Pt + Pd) contains millimeter- to centimeter-size blebs of polycrystalline gersdorffite and nickeline. The gersdorffite-nickeline blebs are concentrated (~6 vol %) in a 10- to 20-cm-thick by 10-m-long lens that occurs at the base of a massive sulfide horizon. The lens is significantly more enriched in Pt and Pd (15–50 ppm Pt + Pd) than typical sulfide horizons in which sulfarsenide and arsenide phases occur only as trace to minor (up to 0.15 vol %) constituents. In the platinum group element (PGE)-rich lens, ~29 and ~74 percent of the bulk rock Pd and Pt, respectively, are dissolved in the sulfarsenide and arsenide minerals. Almost all the remaining Pd and Pt in the lens occur in inclusions of sperrylite, michenerite (PdBiTe), and an unidentified Pd-Bi-Te phase coexisting with inclusions of tellurobismuthite (Bi 2 Te 3 ), altaite (PbTe), and electrum that fill former open spaces (vugs) in gersdorffite and nickeline. In the surrounding sulfide mineralization, PGE mineral inclusions are 4 to 10 times less abundant, and the bulk PGE grade is an order of magnitude lower. Overall, PGE grade on a deposit scale may be controlled by the abundance of gersdorffite and nickeline. Even in minor abundances (e.g., ~1 wt %), sulfarsenide and arsenide minerals may produce economically favorable bulk PGE grades if dispersed throughout barren (PGE-poor) sulfide horizons. The PGE-rich lens may represent the accumulation of either crystallized droplets of an immiscible sulfarsenide melt phase or sulfarsenide phenocrysts that separated from a silicate or sulfide liquid. Arsenic-rich melt or mineral phases extracted (partitioned) the trace metals Pt, Pd, Au, Bi, Te, Sb, Pb, Zn, Ag, and Sn from non–As-bearing phases (silicate liquid, Fe-Ni-Cu sulfide liquid, or monosulfide solid solution [mss]) with inferred values of D As-phase/sulfide on the order of ~10 to 100. Textural, mineralogical, and geochemical observations highlight the importance of As-rich liquids or mineral phases as scavengers of the PGE and other chalcophile metals in komatiite-associated magmatic sulfide environments as well as the potential for high-grade PGE mineralization to occur where komatiites were contaminated by As-rich sediments or metasedimentary rocks.
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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 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| 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".