Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea
Bibliographic record
Abstract
Abstract Slip on the active Mai'iu low‐angle normal fault in Papua New Guinea that dips 15–24° at the surface has exhumed in its footwall a single, continuous fault surface across a >25‐km‐wide dome. Derived from a metabasaltic protolith, the fault zone consists of a <3‐m‐thick zone of gouges and cataclasites that overprint a structurally underlying carapace of extensional mylonites. Detailed microstructural and geochemical data, combined with chlorite‐based geothermometry, reveal changing deformation processes and conditions in the Mai'iu fault rocks as they were exhumed. The microstructure of nonplastically deformed actinolite grains inherited from the fine‐grained (6–35 µm) metabasaltic protolith indicates that shearing at depth was controlled by diffusion creep accompanied by grain‐boundary sliding of these grains together with chlorite neo‐crystallization at T > 275°C–370°C. In a foliated cataclasite unit at shallower crustal levels (T ≈ 150°C–275°C), metasomatic reactions accompanied fluid‐assisted mass transfer processes that accommodated aseismic, distributed shearing; pseudotachylites and ultracataclasites in the same unit indicate that such creep was punctuated by episodes of seismic slip—after which creep resumed. At the shallowest levels (T < 150°C), gouges contain abundant saponite, a frictionally weak mineral that promotes creep on the shallowest dipping (≤24°), most poorly oriented part of the Mai'iu fault. Our field, microstructural and geochemical data of freshly exhumed fault rocks support geodetic, seismological, and geomorphic evidence for mixed seismic‐to‐aseismic slip on this active low‐angle normal fault.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.002 |
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; both teacher heads agree on what is shown here.
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".