Structural, geochronological, and metamorphic characterization of the Monashee décollement and its role in the tectonic evolution of the Canadian Cordillera
Bibliographic record
Abstract
The Monashee décollement (MD) is a crustal-scale shear zone within the southern Omineca belt of the Canadian Cordillera. The MD marks the contact between the autochthonous Precambrian basement core rocks of the Monashee metamorphic complex and the allochthonous rocks of the Lower Selkirk Allochthon. Both packages were metamorphosed at mid-crustal depths (>20 km) but are now exposed at ~ 2200 m elevation. The timing and style of deformation along the MD are disputed. Studies have proposed that the MD is: 1) the base of a mid-crustal ductile “channel”; 2) a complex normal-sense (top-to-the-west) extensional shear zone; or 3) a major reverse-sense (top-to-the-east) contractional shear zone that possibly forms the basal detachment of the Rocky Mountain thrust and fold belt. This study was conducted to investigate those different interpretations through characterizing the detailed temperature-time deformation histories of the rocks within and adjacent to the MD at the Probity Peak field site, ~ 50 km northwest of Revelstoke, British Columbia. This was achieved through: 1) geological field mapping; 2) microstructural analyses of oriented thin sections; 3) quartz c-axis crystallographic preferred orientation (CPO) investigation and opening angle geothermometry; 4) titanium-in-biotite (Ti-in-Bt) geothermometry; and 5) titanite and monazite petrochronology. The data acquired from this study, combined with that from published literature indicate that the MD was active as a reverse-sense contractional shear zone at Probity Peak between ca. 85-80 and 70-65 Ma. The MD was then crosscut by high-angle, brittle-ductile normal faults during extension between ca. 60 and 49 Ma. This extension facilitated exhumation of the Monashee Complex, which continued through Eocene time.
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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 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".