Precise U-Pb dating of reversely magnetized Marathon diabase dykes and implications for emplacement of giant dyke swarms along the southern margin of the Superior Province, Ontario; Radiogenic Age and Isotopic Studies: Report 15
Bibliographic record
Abstract
Earlier paleomagnetic results revealed distinct paleopoles from 2121 +14/.7 Ma normally magnetized (N) and poorly dated, reversely magnetized (R) subsets of the north-trending Marathon diabase dyke swarm north of Lake Superior, suggesting that Nand R subsets are of different ages. U-Pb baddeleyite ages, from independent laboratories, are presented here for two widely separated Marathon R dykes, and indicate magmatic crystallization at 2101.0 " 1.6 and 2101.8 " 1.9 Ma. Marathon R dykes are considerably older than reversed dykes of the northwest-trending 2076 +5/.4 Ma Fort Frances swarm west of Lake Superior, although the two dyke sets were thought to possibly belong to one giant radiating swarm, based on similar paleopoles. However, if a single radiating swarm is correct, the new results imply a relatively long lived (ca. 45 Ma) magmatic plume centre that was tapped in ca. 20 to 25 Ma intervals. Dating of the Marathon Rdykes also establishes the R paleopole as a key- pole that can be used with confidence to establish a more accurate apparent polar wander path and more refined Paleoproterozoic continental reconstructions for Laurentia.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".