Deformation microfabrics of clay gouge, Lewis Thrust, Canada: a case for fault weakening from clay transformation
Bibliographic record
Abstract
Abstract A sequence of bentonite and shale samples in a gouge zone of the Lewis Thrust (Alberta, Canada) that display increasing degree of transformation of clay minerals toward the hanging wall of the thrust has been studied by X-ray diffraction (XRD), X-ray texture goniometry (XTG), scanning electron microscopy (SEM), and transmission and analytical electron microscopy (TEM-AEM), to examine the relations among mineral transformations, microfabrics and fault zone properties. TEM images of authigenic clays show abundant smectite in shale away from the hanging wall, characterized by anastomosing layers with an average orientation that parallels bedding, coexisting with uncommon R 1 illite-smectite (I-S). In the sample nearest the hanging wall, by contrast, the dominant clay is mixed-layered, illite-rich ilite-smectite ( R 1 I-S), coexisting with discrete illite, occurring in individual packets of relatively straight layers with well-defined boundaries. Deformed clay packets are common. Pore space, where packets intesect at high angles to one another and to bedding, is abundant ( c. 25%). The microfabric and proportion of illite of intermediate samples are transitional to these end-members. Inter-layered bentonite samples show properties that are similar to those of shale. TEM observations are supported by quantification of the fabrics using XTG, which shows that the intensity of clay preferred orientation decreases significantly with increasing illitization. These relations imply that faulting was the cause of mineral transformations and formation of secondary pore space. The illitization reaction rate was enhanced both by stress-induced defects in clays, and by increased water/rock ratio resulting from deformation-related pore space, resulting in lowering of the effective stress. The deformation-enhanced reaction thus created a positive feedback for further faulting in clay gouge, leading to enhanced weakening of the fault zone.
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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 | 0.001 |
| Scholarly communication | 0.001 | 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".