The lithosphere-asthenosphere boundary and lithosphere replacement as informed by mantle xenoliths and their host lavas
Bibliographic record
Abstract
Alkaline lavas hosting mantle xenoliths occur in the hot back arc of the Cordillera of western Canada and Alaska and provide constraints on lithosphere thickness (within 5 to 10 km) and controls on the lithosphere-asthenosphere boundary (LAB). Such information is complementary to geophysical investigations of lithosphere strength and deformation in similar continental regions. Barometry of spinel lherzolite xenoliths and alkaline lavas from the Cordillera show LAB depths from 50 to 80 km, and marked thinning of the lithosphere at the Cordillera-craton transition coincident with the Rocky Mountain Trench-Tintina Fault. Similar barometric data globally for continental intraplate lavas show a relatively common lava equilibration depth of 65 to 80 km, that mostly coincide with LAB depths observed by seismology, and with the spinel- to garnet peridotite transition. The LAB is inferred as accumulated partial melt, modulated in depth by mantle solidus depression caused by varying H2O storage capacity across the garnet-spinel peridotite phase change. This mechanism does not explain cases where LAB depths are < 65 km, which instead require locally hotter asthenosphere. In many regions preserving a shallow LAB, foundering and wholesale replacement of mantle lithosphere is invoked. With the exception of North China, mantle xenoliths sampled from continental margins record cooling timescales that appear far longer than required for foundering and replacement in the past 50 Myr. Either cooling histories cannot be adequately modelled using closure/diffusion arguments or wholesale replacement of mantle lithosphere is a dubious process.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".