Alkaline picritic volcanism on northern Ellesmere Island associated with initial rifting of the Sverdrup Basin, Canadian Arctic
Bibliographic record
Abstract
The Caledonian and Ellesmerian orogenies were followed by extension and development of intracontinental rift basins since the late Paleozoic, as represented by the Sverdrup Basin along the Canadian Arctic Islands. The initial rifting was accompanied by pulses of volcanic activity during the Carboniferous and Permian. A new occurrence of mafic volcanic rocks, the “Taconite volcanics” (informal name), was discovered on northern Ellesmere Island between the head of Ayles Fiord and M’Clintock Inlet. The mainly alkali-picritic lavas are exposed within the central part of the Pearya Terrane as an outcrop in faulted contact with upper Carboniferous red beds of the Canyon Fiord Formation. The contact to the Ordovician island-arc volcanic rocks of the Pearya Terrane is unclear. The outcrop is characterized by a small circular magnetic anomaly. Ar–Ar whole-rock geochronology on the volcanic rocks yielded an age of 290 ± 19 Ma suggesting emplacement of the lavas during the early Permian. Whole rock geochemical analyses for eight samples revealed a geochemical affinity to ocean island basalt (OIB) and indicate variable mixing of low-degree melts in the fields of garnet and spinel peridotite (∼80–90 km depth). The involvement of a metasomatized subcontinental lithospheric mantle is indicated by high Pb, Nb, and Ta concentrations. Geochemical differences (as enrichments in Ti, Nb, Zr, and the light rare earth elements (REE)) to the known Carboniferous and Permian spilitic altered basalt occurrences of northwestern Ellesmere and northern Axel Heiberg islands are probably based on differences in the mantle source. The Sr isotope ratios of the Taconite volcanics are primitive ((87Sr/86Sr)t: 0.7037–0.7042) and its Nd isotope ratios are moderately depleted (εNd(t): +2.20 to +2.85) in contrast to the enriched εNd(t) values of the Permian Esayoo formation.
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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) | 0.002 | 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".