A buried Palaeoproterozoic spreading ridge in the northern Nagssugtoqidian orogen, West Greenland
Bibliographic record
Abstract
Abstract Ophiolitic rocks on two small island groups in the northern Nagssugtoqidian orogen, West Greenland, shed new light on the eastern Laurentian Palaeoproterozoic plate-tectonic collage. The islands expose amphibolite-facies (520–550 °C, 2.6–3.0 kbar) tholeiitic pillow lava, black chloritic shale, manganiferous banded iron formation (BIF), podded chert, jasper, graded andalusite–staurolite schist with numerous sills, and terrigenous sandstone, an association that occurs today in oceanic spreading zones undergoing burial in forearc trenches. Deformation is weak, with upright folds preserving original younging. U–Pb detrital zircon ages indicate derivation from Archaean, 1890 Ma, and 1850 Ma sources. Occurring north of the Archaean Aasiaat domain that partly escaped Nagssugtoqidian deformation, the sequence pinpoints a new SSE-dipping Palaeoproterozoic subduction zone that links up in the NE with the Disko Bugt suture at the Nagssugtoqidian–Rinkian boundary. This solves an enigma of the previous plate-tectonic model, in which the Arfersiorfik magmatic arc in the central Nagssugtoqidian orogen was located within its own suture zone, and helps to explain why the Nagssugtoqidian–Rinkian system is so broad. It also explains previously recognized geochemical and Pb-isotopic compositional breaks in orthogneisses in the Kangaatsiaq region, and greatly simplifies correlation with adjacent eastern Canadian orogens in Baffin Island and Labrador.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".