Thermal expansivity and elastic properties of the lithospheric mantle: results from mineral physics of composites
Bibliographic record
Abstract
The elastic properties and the coefficient of thermal expansion (CTE) of the lithospheric mantle are important parameters that affect the results of lithospheric modelling. However, there is still no consensus on which values are the most appropriate to model the lithosphere, and various average values are used for lithospheres of different age, thermal state, and composition. We present an integrated approach to calculate the elastic properties and the CTE of mantle rocks, based on the mineral physics of composites and considering the spatial heterogeneity of the lithospheric mantle. The method considers the dependence of parameters on pressure and temperature, following a procedure based on an extension of the shear-lag model and thermal expansivity systematics. Representative values are calculated for three lithospheric domains: (a) Archean lithosphere, (b) Phanerozoic continental lithosphere, and (c) oceanic lithosphere. For the case of Archean lithosphere, values of CTE between (3.04 and 3.11) × 10 −5 K −1 are found to be suitable for modelling, and a constant depth-derivative for P-waves ∂Vp/∂z ∼ 2.30 × 10 −3 s −1 is estimated. Results for Phanerozoic lithosphere show that no single average value of CTE can be used in modelling. Values range non-linearly between (3.25 and 3.47) × 10 −5 K −1 at pressures equivalent to depths of 25 and 100 km, respectively. The P-wave velocity variation with depth exhibits a decrease in the range of 25–40 km, followed by almost a constant value of ∼8.08 km s −1 between 40 and 60 km, and a systematic increase with a depth-derivative ∂Vp/∂z ∼ 1.12 × 10 −3 s −1 from 60 km downwards. The variation in the CTE is largest in oceanic lithosphere. In young plates (20 Ma), values of the CTE range non-linearly from (3.25 to 3.82) × 10 −5 K −1 at pressures equivalent to depths of 10 and 50 km, respectively. In old oceanic lithosphere ( ∼100 Ma), the CTE is slightly smaller, showing values in the range of (3.0–3.7) × 10 −5 K −1 at 10 and 80 km, respectively, giving a typical average value of ∼3.45 × 10 −5 K −1 . P-wave velocity in young oceanic lithosphere decreases from ∼8.14 to 8.0 km s −1 in the first 30 km, then follows a nearly constant path downwards. In old oceanic lithosphere, on the other hand, a systematic reduction from ∼8.2 to 8.1 km s −1 in P-wave velocities is predicted as depth increases from 10 to 80 km. The effects of heterogeneities in CTE and elastic parameters are particularly noticeable in Archean lithosphere, where difference in predicted elevations and geoid heights can reach values of ≥300 and ∼6 m, respectively, when compared to standard models.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.000 | 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 teacher head, 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".