Sb-enriched ultramafic lamprophyre in the Hemlo Au-Mo deposit of the Superior Province, Canada Evidence for Post-Archean Sb mobility
Bibliographic record
Abstract
An Sb-enriched ultramafic lamprophyre (UML) sill was identified within the Hemlo Au-Mo deposit (David Bell mine) of the Superior Province, Canada. The low SiO 2 (31 wt.%), high TiO 2 (4.2 wt.%), Nb (146 ppm), Ta (10 ppm), Cr (900 ppm), and Ni (720 ppm) contents, as well as the unusual mineralogy (olivine, perovskite, Ti-rich phlogopite, calcite) of the sill are consistent with the geochemistry and mineralogy of other ultramafic lamprophyres on the global scale. The fine-grained, dark greenish-black sill has unchilled margins and intrudes basaltic and felsic fragmentals. The lamprophyre contains 794 ppm Sb, which is concentrated in fine-grained ullmannite, a Ni(Co)-Sb sulfide, within pervasively altered olivine. The presence of ullmannite in altered olivine within the UML implies that Sb was mobilized after the emplacement of the sill. Because Sb is considered to be one of the pathfinder elements for Au at Hemlo, and because antimony sulfides (including ullmannite) and arsenides are commonly associated with Au at the Hemlo camp, the addition of Sb to the Proterozoic lamprophyre suggests that Sb mobilization (and by inference, Au) possibly occurred throughout the tectonic evolution of the deposit. This has implications for genetic models of Hemlo, as cross-cutting relationships of Archean plutons and multi-phase deformation of the deposit make it difficult to distinguish between the actual timing of Au, Mo and Sb introduction and their subsequent re-mobilization and re-concentration into structural traps during various stages of deformation. It also re-opens questions concerning the genetic link between gold metallogeny and tectonic evolution of the region.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".