Depth of Ancient Seismicity Along the Woodroffe Thrust (Central Australia): Constraints From Pseudotachylytes in Peraluminous Gneisses
Bibliographic record
Abstract
Abstract The Woodroffe Thrust (WT) is a regional‐scale mylonitic shear zone that developed during the Petermann Orogeny (630–520 Ma) in lower to mid‐crustal rocks of the Musgrave Ranges, central Australia. In the upper part the WT hosts the largest volume worldwide of tectonic pseudotachylytes (coseismic quenched frictional melts). The pseudotachylytes were only marginally reworked along the mylonitic belt marking the WT, which mainly derived from the footwall amphibolite‐facies rocks. Mid‐crustal conditions of deformation along a shallowly dipping (<6°) WT were previously inferred from estimates of the P‐T conditions of mylonitization along a regional transect in the N‐S direction of thrusting. However, the pressure estimates were subject to large uncertainties. To better constrain the ambient conditions of the ancient seismic faulting along the WT, we investigate pseudotachylytes within peraluminous gneisses, a rock type more sensitive to P‐T changes in the range of interest. Microstructural analysis allows the sequence of minerals (corundum, sillimanite, cordierite, andalusite, kyanite and garnet) developed during melt quenching and subsequent solid‐state growth to be established. Critical observations are the growth of andalusite during pseudotachylyte cooling, constraining faulting at <0.45 GPa, and of kyanite during the immediately following ductile reactivation of pseudotachylytes. Seismic faulting is inferred to have occurred at ambient conditions of ∼0.4 GPa and 450°C, that is at much shallower conditions than previously assumed. These new P‐T estimates imply an inclination of 20–25° of the WT, if the main stage of seismic faulting and mylonitization along the WT were coeval.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".