The Archean Hammond Reef Deposit (Canada): Formation of an Orogenic Gold Deposit in a Contractional Step-Over Zone Along a Major Strike-Slip Fault System
Bibliographic record
Abstract
Abstract The Hammond Reef deposit is located within the south-central region of the Wabigoon subprovince of the Archean Superior province, Canada. The deposit is hosted by the NNE-trending Marmion shear system, which straddles the contact between the 2890.2 ± 1 Ma Diversion stock and ca. 3000 Ma Marmion batholith. The shear system consists of localized fault-controlled zones of white mica (± carbonate) alteration and shearing, superposed on a wider zone of chlorite-carbonate (± white mica) alteration. Multiple shear sense indicators, including the deflection of mylonitic foliations in shear zones, asymmetrical folds, and shear bands, suggest that the Marmion shear system is a major sinistral transcurrent fault system. The deposit occurs along an ENE-trending segment of the Marmion shear system, where it is associated with hydrothermal quartz breccias and quartz-chlorite-carbonate veins, which were emplaced during the white mica (± carbonate) alteration. Gold is present as disseminated grains in the veins and breccias and as microinclusions and fracture fill in pyrite grains within the white mica–altered wall rocks. New monazite U-Pb ages suggest that the deposit formed at ~2700 Ma during the main orogenic event in the Wabigoon subprovince. NNW-directed shortening during this event resulted in sinistral transcurrent displacement along NNE-trending faults of the Marmion shear system and contraction across ENE-trending segments. Increased fracturing and brecciation due to contraction across these segments channelized the migration of hydrothermal fluids and the precipitation and concentration of gold. The ENE-trending segments represent step-over zones at the terminations of en échelon, NNE-trending, transcurrent faults, which became linked by the formation of throughgoing, ENE-trending faults. Thus, Hammond Reef is an excellent example of an orogenic gold deposit that formed in a contractional step-over zone between two right-stepping sinistral transcurrent faults.
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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) | 0.000 | 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".