Paleoproterozoic gold and its tectonic triggers and traps: implications from Re-Os sulphide and U-Pb detrital zircon geochronology, Lynn Lake, Manitoba
Bibliographic record
Abstract
Orogenic Au deposits require a trigger to transport auriferous fluids from their deep-seated source regions to their depositional site in the mid- to upper-crust. Defining the tectonic trigger of Au ore systems requires precise age constraints. Herein we address that knowledge gap with new Re-Os sulphide (arsenopyrite and pyrite) and U-Pb detrital zircon geochronology results from the Lynn Lake greenstone belt of the Paleoproterozoic Trans-Hudson Orogen, Manitoba, Canada. We document an early-stage of Au-rich veins (ca. 1.82 Ga) that are coeval with syenitic magmatism (1.83-1.82 Ga) and immediately post-date new ages for the opening and closure of synorogenic basins (1.84-1.83 Ga) and late-stage arc magmatism (1.84-1.83 Ga). Together these data point to the importance of stalled subduction and upwelling asthenosphere as possible triggers for fluid release during the earliest stages of continental collision between the Hearne, Superior, and Sask cratons. New dating further documents a second, overprinting generation of auriferous fluids (ca. 1.78 Ga) that post-dates peak metamorphism (ca. 1.81 Ga). These late-stage fluids were driven by a second thermal pulse (ca. 1.78 Ga), which, based on the timing of coeval, crustally derived pegmatitic dykes, may be related to crustal thickening and/or another unrecognized subcrustal heat source. Mineral exploration should focus on the large-scale architecture that is required to focus multiple pulses of auriferous fluids to the same depositional trap over the lifespan of an orogen.
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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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".