MazatzalLabradorian-age (1.71.6 Ga) ductile deformation of the South Range Sudbury impact structure at the Thayer Lindsley mine, Ontario
Bibliographic record
Abstract
The Thayer Lindsley mine is located in the South Range of the Sudbury impact structure, near the contact between the 1.85 Ga Sudbury Igneous Complex (SIC) and the Paleoproterozoic Southern Province. NiCu ore zones at the mine are strongly deformed within a southeast-dipping, lower amphibolite-grade shear zone, which offsets the contact between the SIC and Southern Province rocks. Numerous shear sense indicators, including shear bands, drag folds, and δ- and σ-type rotated porphyroclasts, consistently indicate south-over-north, reverse, dip-slip movement parallel to the mineral stretching lineation in the shear zone. The attitude, slip direction, and metamorphic grade of the shear zone are similar to those of the regional northeast-striking South Range Shear Zone that formed during post-impact, northwest-directed ductile contraction of the Sudbury impact structure. The South Range Shear Zone is generally interpreted as a ca. 1.91.8 Ga Penokean structure. Anhedral brown titanite grains from the Thayer Lindsley shear zone yield a mean 207Pb/206Pb Penokean age of 1815 ± 15 Ma. These grains are mantled by younger, syntectonic, colourless titanite, which have a mean 207Pb/206Pb age of 1658 ± 68 Ma. This younger age suggests that the South Range and Thayer Lindsley shear zones may have formed during a 1.71.6 Ga collisional tectonic event that is recorded along the southeast margin of Laurentia from the southwest USA. (Mazatzal Orogeny), through the mid-continent to Wisconsin, and as far northeast as Labrador (Labradorian Orogeny). 40Ar/39Ar analyses indicate post-tectonic thermal resetting of biotite occurred at 1477 ± 8 Ma during felsic plutonism across the Sudbury area.
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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 | 0.002 | 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) | 0.006 | 0.001 |
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".