Late Jurassic flare‐up of the Coast Mountains arc system, NW Canada, and dynamic linkages across the northern Cordilleran orogen
Bibliographic record
Abstract
Abstract Short‐lived, high‐volume magmatic events or flare‐ups in Cordilleran‐style accretionary systems are presumably triggered by the rapid underthrusting of melt‐fertile lithosphere beneath a continental arc during extreme retroarc shortening. New zircon U‐Pb age and trace element geochemical studies of the Coast Mountains batholith were conducted to test this hypothesis and investigate cross‐orogen linkages between the Coast Mountains arc system and adjacent retroarc elements of the Canadian Cordillera. Late Jurassic (155–147 Ma) granitoids of the Saint Elias plutonic suite in southwestern Yukon were emplaced during a widespread magmatic event and correspond to an intrusive rate of ~350 km2/Myr, analogous to the scale of 160–150 Ma flare‐up activity in the Sierra Nevada batholith. The timing of Late Jurassic high‐volume magmatism was coincident with forearc and intraarc deformation events along the length of the Coast Mountains arc from Alaska to British Columbia. Whole‐rock and zircon rare earth element geochemical results from the Saint Elias plutonic suite confirm that continental lithosphere was a key source component for Late Jurassic granitoids, which strengthens the implied relationship between high‐volume arc magmatism and crustal recycling. Well‐documented episodes of late Middle to early Late Jurassic hinterland thrusting and metamorphism in the Intermontane and Omineca belts of the Canadian Cordillera preceded this high‐volume event and therefore support the hypothesis that retroarc shortening was dynamically linked to flare‐up activity. Late Jurassic magmatism was followed by a 140–125 Ma lull in most of the Coast Mountains batholith, which may be linked to ridge subduction, lithospheric delamination, mantle cooling, or plate reorganization.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| 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".