Reassessing the timing of high-strain deformation in the Strangways Metamorphic Complex, Central Australia, by <i>in situ</i> mica Rb–Sr and titanite U–Pb geochronology
Bibliographic record
Abstract
Dating the timing of deformation within shear zones is critical to quantifying orogenic processes and developing time-resolved regional tectonic frameworks. Such work requires the integration of detailed microstructural analysis with in situ geochronology to quantify when deformation mechanisms were active at the micro-scale. The Proterozoic, granulite-facies Strangways Metamorphic Complex was exhumed during the Devonian to Carboniferous intracontinental Alice Springs Orogeny. New microstructural observations, quartz c -axis orientation analyses, mica chemistry, Ti-in-biotite thermometry, in situ mica Rb–Sr and titanite U–Pb geochronology outline a detailed history of ductile shearing across the complex. Movement along the north boundary shear zone of Strangways Metamorphic Complex appears to have initiated c. 382 Ma, preceding peak metamorphism in the area during the Alice Springs Orogeny. Widespread reverse-sense ductile shearing occurred within the Strangways Metamorphic Complex between c. 365 and 355 Ma, and correlates with rapid cooling of the region. Late-stage ductile deformation is recorded at c. 335 Ma, likely reflecting the terminal exhumation of the Strangways Metamorphic Complex. Finally, the new in situ muscovite and biotite Rb–Sr data collected herein permit comparison with previous two-point mica Rb–Sr isochrons and 40 Ar– 39 Ar dates from the same specimens. In the rocks analysed, the biotite Rb–Sr system returned dates similar to the previous 40 Ar– 39 Ar white mica dates, perhaps indicating a similar effective closure temperature. Supplementary material: Test results and previous geochronology data from the Alice Springs Orogeny are available in tabular form at https://osf.io/yjp24/?view_only=0bf5bec9f5c94a1aa4fb413320ec24e8
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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 | 0.001 | 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".