The effect of impact-generated heterogeneities and discontinuities on the subsequent weathering of impactites: insights from laboratory experiments
Bibliographic record
Abstract
Impact cratering is an important geological process that affects all planetary bodies in our solar system. As rock breakdown plays a vital role in the evolution of landforms and sediments on a planetary scale, it is crucial to assess the role of inheritance in the subsequent breakdown of impactites (impact rocks). The shock pressure of several gigapascals generated during the impact can exceed the effective strength of target lithology by three to four orders of magnitude and is responsible for melting, vaporisation, shock metamorphism, pore collapse, vesiculation fracturing and fragmentation of rocks. Environmental conditions and heterogeneities in rock properties exert an important control in rock breakdown. Similar to other subaerial rocks, impactites are affected by a range of rock breakdown processes. In order to better understand the role of low-shock inheritance on rock breakdown, a rock breakdown experiment was conducted in a simulated environmental cabinet under conditions similar to terrestrial semi-arid conditions. We cycled temperature (-2 to 35°C) and relative humidity (13-45%) through 39 accelerated diurnal cycles (each of 8 hours duration). We used 41 impactite samples in the experiment that included low shocked sedimentary and crystalline rocks, impact melt rocks and impact breccias. Mechanical (Equotip and weighing), photographic (photographic monitoring), microscopic and solid-state methods (petrographic microscopy, powder X-ray diffraction, scanning electron microscopy, X-ray computed tomography) were used to characterise the rock samples relative to unshocked rocks, and to assess the shock related changes before and after the experiments. The low shocked sedimentary rocks showed a decrease in porosity by 38% (Coconino Sandstone) and 88% (Moenkopi Sandstone) compared to unshocked counterparts. Macrofractures of 0.1-0.2 mm and microfractures 0.1-5 µm in aperture were observed in all types of impactites. The results showed that impactites exhibited an accelerated decline in strength compared to non-impacted control samples. However, rock type and impact deformation history were key parameters controlling the rate of deterioration.
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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 | 0.001 |
| 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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".