Petrochronology of the East Pond Metamorphic Suite eclogite, Baie Verte Peninsula, Newfoundland, Canada
Bibliographic record
Abstract
Abstract The East Pond Metamorphic Suite (EPMS) in the Baie Verte Peninsula, Newfoundland, Canada, provides a unique record of tectono-metamorphic processes during the Middle Ordovician Taconic orogeny. This study utilizes petrochronology to investigate the complex evolution of the EPMS eclogites, revealing new insights into the subduction and exhumation history of parts of the early Paleozoic Laurentian margin. U-Pb geochronology of zircon, rutile, titanite, and apatite—integrated with trace element data—as well as Rb-Sr mineral isochrons constrain the timing and conditions of metamorphism. We also document late Taconic magmatism on the Laurentian margin, indicated by zircon U-Pb dates from pegmatite intrusions crosscutting the eclogite boudins at ca. 444 Ma. These metamorphic rocks exhibit a multistage metamorphic history with eclogite-facies conditions at ca. 483 Ma, followed by retrograde amphibolite-facies overprint during protracted deformation. Subsequent stages of exhumation and cooling are recorded by Rb-Sr mineral isochrons at ca. 460 Ma as well as titanite and apatite at ca. 459 Ma and ca. 452 Ma, respectively. New constraints on exhumation rates indicate that a protracted phase of residence at ultrahigh-pressure conditions was followed by a short-lived pulse of rapid ascent and late Taconic magmatism, suggesting that exhumation of the EPMS was buoyancy driven and modulated by transient thermal perturbations linked to changes in deep subduction dynamics. We establish a new chronological framework providing insights into the tectono-metamorphic evolution of the Laurentian margin and the Notre Dame arc during the Middle Ordovician Taconic orogeny. Additionally, we link tectonic and magmatic events during subduction and collision, highlighting the complex interplay between these processes at different crustal levels.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 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) | 0.003 | 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".