Geodynamic studies of southwestern Canada: subduction zone processes and backarc mantle dynamics
Bibliographic record
Abstract
Geodynamic models allow insights into the processes that control lithosphere structure and evolution. Here, we review geodynamic studies along a profile across southwestern Canada, from the Cascadia subduction zone into the Laurentian craton. Geophysical and geological observations show distinct changes in thermal structure along this profile. One major change is between the cool forearc and hot volcanic arc. This marks the transition from (1) a stagnant forearc mantle that is cooled by the subducting Juan de Fuca Plate to (2) an advection-dominated arc region, where high temperatures arise from mantle flow driven by the subducting plate (corner flow). High temperatures occur for 400–500 km east of the arc to the Rocky Mountain Trench (RMT), where lithosphere thickness increases from 60 to 70 km below the Cordillera to >200 km below the craton. The timing of Cordillera lithosphere thinning is debated. A long-lived (>100 Ma) thin lithosphere inherited from earlier tectonics requires vigorous convection of a weak, hydrated mantle. Conversely, thinning may have occurred through gravitational removal of the lower lithosphere in the Eocene. Models show that a removal event only allows for a short-lived thin lithosphere (∼25 Myr), owing to conductive cooling. Even if there was Eocene delamination, the present-day thin lithosphere requires small-scale convection in the Cordillera mantle. The thermal contrast across the RMT is enhanced by edge-driven convection at the Cordillera–craton lithosphere step. The step itself is an enigmatic feature, and its long-term preservation requires that the craton mantle lithosphere is strong (dry) with moderate chemical depletion.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.007 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 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".