CHEMICAL CONTROLS ON THE DISTRIBUTION OF CRITICAL METALS IN THE HACKETT RIVER ZN-PB-CU-AG MAIN ZONE VOLCANOGENIC MASSIVE SULFIDE DEPOSIT, NUNAVUT
Bibliographic record
Abstract
The 2.68 Ga Zn-Pb-Cu-Ag Hackett River Main Zone volcanogenic massive sulfide (VMS) deposit is in the Hackett River Greenstone Belt (Nunavut), part of the Slave Craton. VMS deposits are polymetallic and host a variety of critical metals. Samples from a drill hole that stratigraphically transects the mineralization were studied. Within this hole, copper is enriched in the footwall, and this decreases in abundance higher in the mineralized lens; this is followed upward by enrichment in Zn, and finally Pb enrichment towards the top of the mineralized lens. “Ore” minerals present are: chalcopyrite, galena, pyrite, pyrrhotite, sphalerite, and tetrahedrite. Samples were analyzed for bulk geochemistry, and mineralogy and mineral chemistry by SEM-MLA and LA-ICP-MS. The residence, zonation, and deportment of fifteen critical metals (Mn, Mn, Cd, Co, Ni, As, Sb, Ag, Bi, Se, Sn, In, Ga, Ge, Mo, Tl) were determined. Towards the stratigraphic top of the mineralized lens Ag (and Sn) is resident in tetrahedrite and galena. Galena is the dominant host for these elements where tetrahedrite is not present (i.e., not precipitated), suggesting that both elements are controlled by temperature of the mineralizing fluid. Cadmium, Mn, and Ga reside in sphalerite. Manganese2+ and Cd2+ substitute for Zn2+ in the sphalerite crystal structure. Similarly, Ga2+ substitutes for Zn2+ and there is element competition between Ga and Zn for space in the sphalerite crystal lattice. Bismuth and Tl occur as substitutions for Pb due to “incremental” crystallization from a circulating hydrothermal fluid, wherein the “reservoir” of these elements is quickly depleted once galena starts to precipitate. The highest Co concentrations in pyrite are toward the middle of the mineralized lens and the highest Ni concentrations occur toward the top of the mineralized lens. Both Co2+ and Ni2+ substitute for Fe2+ in the pyrite crystal structure. The difference in their enrichment through the mineralized lens indicates that the elements are in competition with each other for residence in pyrite. Arsenic and Se are enriched in pyrrhotite and chalcopyrite at the base of the lens. Higher in the mineralized lens As is enriched in pyrite and tetrahedrite, and Se is enriched in galena.
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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 | 0.000 |
| Science and technology studies | 0.001 | 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".