Shear wave properties and Poisson's ratios of ultrahigh‐pressure metamorphic rocks from the Dabie‐Sulu orogenic belt, China: Implications for crustal composition
Bibliographic record
Abstract
Shear wave velocities (Vs), anisotropy, and shear wave splitting have been measured at pressures up to 600–800 MPa for ultrahigh‐pressure (UHP) metamorphic rocks from the Dabie‐Sulu orogenic belt, China, with a focus on three types of eclogites. Type 1 eclogites are coarse‐grained, unaltered samples showing high densities and high Vs values (4.85 ± 0.06 km/s at 600 MPa); type 2 eclogites are fine‐grained, sheared samples with intermediate Vs values (4.53 ± 0.04 km/s at 600 MPa); and type 3 eclogites are overprinted by amphibolite facies metamorphism and display low Vs values (4.33 ± 0.09 km/s at 600 MPa). The compositional layering and retrograde metamorphism can result in significant anisotropy and shear wave splitting in eclogites, suggesting their plausible contribution to seismic anisotropy in the lower crust, upper mantle, and particularly in subducted slabs. Integrating our P and S wave velocity results with reliable data from previous studies, we estimated the pressure and temperature derivatives of Vp, Vs, and Poisson's ratios for common rock types in the UHP metamorphic belt. The geometric means were used as a mixture rule to invert the lithological and chemical compositions of the layered crust from seismic refraction velocities. The inferred crustal composition suggests that the eclogite‐bearing UHP rocks are tectonic slices of crust that have been thrust along a series of shear zones during the continental collision between the north China and Yangtze cratons, over a normal UHP‐free middle lower crust with overall intermediate composition.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| 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".