Paleomagnetic poles of mafic dyke swarms from the North China craton and their relevance to the reconstruction of the supercontinent Columbia.
Bibliographic record
Abstract
One geomagnetic pole and two virtual geomagnetic poles (VGPs) are now available from U-Pb dated dyke swarms/ individual dykes from the Eastern Block, Central Zone and Western Block of the North China craton. The precise baddeleyite U-Pb age of Hengshan GU dyke in the Central Zone is 1769±3Ma and is part of the Taihang dyke swarm. This swarm has yielded a paleomagnetic pole position at Plat =36°N, Plong = 247°E(dp = 2°, dm =4°). A dyke at location DY in the Eastern Block of the North China craton yields a baddeleyite U-Pb age of a baddeleyite 1620.8±6.9Ma, and a VGP at Plat =6.9°N, Plong = 81.9°E {dp = 4.31°,dm=6.09°). A nearby dyke at site LW4 gives a zircon SHRIMP U-Pb age of 1157±18Ma, and a VGP at Plat =27.1°N, Plong = 162°E( dp = 15.8°, dm = 18.7°). Although secular variation has not been removed from the Shandong data, comparison of these three paleomagnetic pole positions of the North China craton with the Mesoproterozoic APWP of the Canadian Shield allows a continental reconstruction whereby the North China craton joined the supercontinent Columbia with the Canadian Shield from 1800 to 1600Ma, and the North China craton separated from the Canadian Shield sometime between 1600 to 1200Ma in response to the final break-up of the supercontinent Columbia.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".