Paleomagnetism, U–Pb geochronology, and geochemistry of Lac Esprit and other dyke swarms, James Bay area, Quebec, and implications for Paleoproterozoic deformation of the Superior Province
Bibliographic record
Abstract
An extensive set of north- to northwest-trending diabase dykes, termed the Lac Esprit swarm, is identified in the Superior Province east of James Bay based on geological mapping and a distinctive paleomagnetic pole (61.7°N, 169.1°E, dm = 7.7°, dp = 5.5°). The Lac Esprit swarm yields a U–Pb baddeleyite age of 2069 ± 1 Ma similar to that of the 2076 +5 –4 Ma Fort Frances swarm of the western Superior Province. Their paleomagnetic declinations differ by 23° ± 12° after correction to a common reference locality. The difference is likely due mainly to counterclockwise rotation about a vertical axis of the Fort Frances area relative to the Lac Esprit area. Differential rotation of 10°–20° has been proposed more locally across the Kapuskasing Structural Zone separating the eastern and western Superior Province in earlier paleomagnetic studies of ca. 2450 Ma Matachewan and 2170 Ma Biscotasing dyke swarms. Thus, relative rotation may have involved the entire eastern and western Superior Province, perhaps in response to collisional events associated with the Trans-Hudson Orogen to the north or the Penokean orogen to the south, or in response to rifting beneath Hudson Bay. Other dykes in the study area are interpreted from a combination of paleomagnetism, trend, and geochemistry to belong to the Senneterre, Matachewan, and Mistassini swarms. The 2216 Ma Senneterre dykes form part of a giant swarm that fans across the eastern Superior Province. Paleomagnetic directions and geometry of this swarm rule out substantial block rotations within the eastern Superior Province since dyke emplacement.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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".