Elastic and Seismic Properties of Dabie‐Sulu Ultrahigh Pressure Metamorphic Rocks
Bibliographic record
Abstract
Abstract: Lamé modulus (λ) and shear modulus (μ) are among the most important, intrinsic, elastic constants of rocks. Using λ and μ could be much more advantageous than using P‐ and S‐wave velocities (Vp and Vs). Here we quantified these equivalent isotropic elastic moduli for 115 representative rocks from the ultrahigh pressure (UHP) metamorphic terrane of the Dabie‐Sulu erogenic belt (China) and their variations with pressure (P), temperature (T), density (p), Vp, Vs and minera logical composition. Both moduli increase nonlinearly and linearly with increasing pressure at low (<200–300 MPa) and high (>200–300 MPa) pressures, respectively. In the regime of high pressures, λ and μ decrease quasi‐linearly with increasing temperature with temperature derivatives dλ/dT and dμ/dT generally in the range of –10 × 10–3 to –1 × 10–3 GPa/°C. Dehydration of water‐bearing minerals such as serpentine in peridotites and chlorite in retrograde eclogites results in an abrupt drop in λ while μ remains almost unchanged. In λ‐ρ, μ‐ρ and λ‐μ plots, the main categories of UHP rocks can be characterized. Serpentinization leads to significant decreases in μ and λ as serpentine has extremely low values of λ, μ and ρ. Eclogites, common mafic rocks (mafic gneiss, metagabbro and amphibolite), and felsic rocks (orthogneiss and paragneiss) have high, moderate and low μ and λ values, respectively. For pyroxenes and olivines, λ increases but μ decreases with increasing Fe/Mg ratios. For plagioclase feldspars, both λ and μ exhibit a significant positive correlation with anorthite content. SiO2‐rich felsic rocks and quartzites are deviated remarkably from the general trend lines of the acid‐intermediate‐mafic rocks in Vs‐ρ, μ‐ρ, λ‐Vp, λ‐Vs and μ‐λ diagrams because quartz has extremely low λ (∼8.1 GPa) and p (2.65 g/cm3) but moderate μ (44.4 GPa) values. Increasing the contents of garnet, rutile, ilmenite and magnetite results in a significant increase in the λ and μ values of the UHP metamorphic rocks. However, either λ or μ is insensitive to the compositional variations for pyralspite (pyrope‐almandine‐spessartine) solution series. The results provide potentially improved constraints on characterization of crustal composition based on the elastic properties of rocks and in situ seismic data from deep continental roots.
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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 | 0.000 | 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".