U-Pb geochronology of the Neoarchean Swayze sector of the southern Abitibi greenstone belt
Bibliographic record
Abstract
Precise U-Pb zircon geochronology of the Swayze greenstone belt reveals a 45 Ma history of volcanism with 19 ages ranging from 2739 Ma to 2695 Ma. Seven U-Pb ages demonstrate the coeval nature of regionally extensive 2.73 Ga iron-formation, which serves as a key stratigraphic marker correlative across major deformation zones. Age correlations are consistent with an upward-younging stratigraphic succession without major tectonic breaks or disruption, which can be correlated with equivalent stratigraphy across the southern Abitibi greenstone belt. The youngest volcanic rocks are interlayered with greywackes for which detrital zircons from two samples establish maximum ages of deposition of 2683 ± 6 Maand 2695 ± 1 Ma. As the detrital zircon ages are mostly younger than 2704 Ma, the provenance of these sediments is inferred to be exclusively volcanic rocks of the immediately lower pile. Detrital zircons from the youngest sedimentary rocks, sandstone of the unconformable and fault-bounded Ridout Group, provide a maximum depositional age limit of 2688 ± 2 Ma. Older detrital zircon ages, in the 2742 to 2735 Marange, are consistent with deeper erosional excavation of source rocks and more active tectonics at the time of deposition. The oldest plutonic rocks of 2.74 Ga are coeval with the oldest volcanic rocks recorded and no geochronological evidence for pre-existing basement has been found. Plutonism continued after cessation of extensive volcanism, including 2686 Ma to 2680 Ma syntectonic (D2) granitoids and post-tectonic granitoids as young at 2.66 Ga. Titanite ages of 2615 ± 3Ma to 2540 ± 4Ma are interpreted in terms of crystal growth from late-stage fluids.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.000 | 0.001 |
| 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".