Mid–Late Ordovician magmatism and metamorphism along the Gander margin in central Newfoundland
Bibliographic record
Abstract
Fieldwork coupled with U–Pb dating has clarified the relationships between the Exploits and Gander-derived rocks in central Newfoundland during the Mid-Ordovician opening of the Exploits back-arc basin, reinforcing correlation across the peri-Gondwanan segments of the Appalachian–Caledonian orogen. We have separated a new back-arc-related unit, the Red Cross Group, from the arc-related Victoria Lake Supergroup. This group includes 466 ± 3 Ma felsic volcanic rock interlayered with alkali basalt–enriched mid-ocean ridge basalt, 457 ± 6 Ma gabbro, Llanvirn–Caradoc normal mid-ocean ridge basalt–island arc tholeite, limestone, black shale and mélange. Locally the Red Cross Group is in parautochthonous contact with low-grade Gander psammite. This contact was overrun by the Meelpaeg Metamorphic Nappe during the Devonian. The nappe contains Gander metapsammite (Meelpaeg Subzone) and the coticule-bearing Howley Waters Complex (Exploits), which hosts 467 ± 3 Ma felsic porphyry. The Gander and Exploits metasediments in the nappe are stitched by Arenig–Llanvirn granite (467 ± 6 Ma and 468 +3.5/−3 Ma) and Caradoc intrusions (458 ± 3 Ma and 454 ± 2 Ma). Metamorphic monazite (462 ± 1 Ma) and titanite (460 ± 3 Ma) from the nearby Mount Cormack Subzone (Gander) indicate the coeval formation of a low-pressure–high-temperature metamorphic dome. The widespread presence of Caradoc magmatism suggests that the width of the back-arc basin remained relatively narrow.
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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 | 0.001 |
| 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".