Imaging Hales Discontinuity beneath India: Seismological and Petrological Model
Bibliographic record
Abstract
We model the depth and Vs structure of the Hales discontinuity (H-D) beneath Eastern Dharwar Craton (EDC) and Southern Granulite Terrain (SGT) using P-wave receiver function (P-RF) analysis and joint inversion with Rayleigh wave phase velocity dispersion. We calculate P-RFs at higher frequency (fmax 0.46 Hz), compared to previous studies, to show that the P-to-S converted phase from the H-D (Phs) is distinct from the crustal reverberations. The Phs at stations in the EDC arrive at ~10 s beneath GBA, and ~11 s beneath HYB. From joint inversion the H-D is modeled at 97 ± 5 km and 108 ± 5 km depth, with 5% and 3% Vs increase, beneath GBA and HYB, respectively. For KOD, in SGT, the Phs coincides with the mid-crustal PpSs+PsPs reverberation at most ray-parameters, causing destructive intereference. This explains the apparent absence of Phs in previous studies. We isolated P-RFs where Phs is distinct at ~10.5 s and model it at depth of 101 ± 5 km with Vs increase of 3%. We demonstrate through forward calculation that the spinel-garnet mineral transformation cannot explain the H-D Vs increase. From data of mantle xenoliths in the Wajrakarur kimberlite field, Southern India, we calculate Vs of mantle peridotite and eclogite, using published bulk rock compositions through Perple-X. At the H-D depth and temperature derived from Indian shield geotherm, we observed a perfect match to the Vs. We hypothesize that H-D marks the surface of a paleo-subducted eclogitic oceanic slab embeded within the upper mantle peridotite. Observations of mantle faults within the Canadian lithosphere, at similar depth, has been related to relict-subduction zones and therefore independently supports our model.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".