Common depth of slab‐mantle decoupling: Reconciling diversity and uniformity of subduction zones
Bibliographic record
Abstract
Processes in subduction zones such as slab and mantle‐wedge metamorphism, intraslab earthquakes, and arc volcanism vary systematically with the age‐dependent thermal state of the subducting slab. In contrast, the configuration of subduction zones is rather uniform in that the arc is typically situated where the slab is ∼100 km deep. Toward reconciling the diversity and uniformity, we developed numerical thermal models with a nonlinear mantle rheology for seventeen subduction zones, spanning a large range of slab age, descent rate, and geometry. Where there are adequate observations, such as in Cascadia, northeast Japan, and Kamchatka, we find that surface heat flows can be explained if the interface between the slab and the mantle wedge is decoupled to a depth of 70–80 km. Models with this common decoupling depth predict that the region of high mantle temperatures and optimal fluid supply from the dehydrating slab, both required for melt generation for arc volcanism, occurs where the slab is ∼100 km deep. These models also reproduce the variations of the metamorphic, seismic, and volcanic processes with the thermal state of the slab. The shallow decoupling results in a stagnant fore arc whose thermal regime is controlled mainly by the subducting slab. The deeper coupling leads to a sudden onset of mantle wedge flow that brings heat from greater depths and the back arc, and its thermal effect overshadows that of the slab in the arc region. Our results serve to recast the research of subduction zone geodynamics into a quest for understanding what controls the common depth of decoupling.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".