Mantle heterogeneities and their significance: results from Lithoprobe seismic reflection and refraction – wide-angle reflection studiesThis article is one of a series of papers published in this Special Issue on the theme<i>Lithoprobe — parameters, processes, and the evolution of a continent</i>.Lithoprobe Contribution 1486.
Bibliographic record
Abstract
Within Lithoprobe’s 10 transects, data from more than 20 000 km of multichannel seismic (MCS) reflection profiling and 12 refraction – wide-angle reflection (R/WAR) surveys were acquired. While the main results related to crustal structure, the data also indicated substantial heterogeneity in the lithospheric mantle. Images of fossilized subduction zones from the Eocene to the Neoarchean demonstrate that current plate tectonic processes have been active for more than 2.6 Ga. The Canadian Cordillera has a thin (50–60 km) lithosphere that is likely receiving some dynamic support from the asthenosphere below. Vestiges of the last stage of accretionary tectonic processes that formed the Archean Superior craton are indicated by an unusual anisotropic high velocity layer that may represent relic oceanic lithosphere. Within the Paleoproterozoic Trans-Hudson Orogen, a restricted region of upper mantle P-wave velocity anisotropy is identified with the continental collision between the bounding Hearne and Superior cratons. In the Archean Hearne and Wyoming provinces, two dipping structures within the sub-crustal lithosphere are interpreted as subduction features related to the assembly of the two cratons. Finite-difference modeling of long-offset data (over 1300 km) reveals fine-scale heterogeneities within a layer between 90 and 150 km in the continental lithosphere, perhaps formed through lateral flow or deformation within the upper mantle. Based on Lithoprobe data, heterogeneities within the lithospheric mantle are reasonably common. They have a wide range of seismic signatures, include many different types and show differing scales. Nevertheless, their extent in the lithospheric mantle is considerably less than in the crust.
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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".