Evidence for Post‐Assembly Modification of Western Laurentia by Back‐Arc Extension
Bibliographic record
Abstract
Abstract The crystalline crust that underlies the Western Canada Sedimentary Basin in northern Alberta is composed of tectonic domains that accreted to the margin of the Archean Rae province of western Laurentia, ca. 2.1‐1.8 Ga. Previous tectonic models in this region invoke complex plate dynamics, including oppositely verging subduction zones, to explain the assembly of various geologic domains. In this paper, we introduce a new tectonic model that invokes back‐arc extension within the Chinchaga Domain (CD). The basement crust in the CD hosts a vast, mid‐crustal reflection sequence (Winagami Reflection Sequence), previously interpreted as a mafic sill complex that intruded into an atypically wide domain of Paleoproterozoic arc magmatism. The latter has been interpreted to have formed during Paleoproterozoic tectonic assembly through near‐synchronous closure of multiple small oceanic basins and/or magmatism in a plate interior setting. Based on a reinterpretation of regional geophysical data and post‐compressional fabrics observed by re‐examination of drill cores, we propose that observed temporal relationships and present‐day configuration of Paleoproterozoic arcs is better explained by post‐assembly extension of the Chinchaga Domain. The proposed post‐assembly modification is analogous to the recent tectonic evolution of the Basin and Range and can be explained through back‐arc extension linked to slab rollback and/or a proximal coeval transform plate boundary. Our model implies a back‐arc setting for the Winagami sill complex; it also provides a tectonic framework for explaining the origin of an enigmatic low δ18O anomaly (Kimiwan anomaly) and reactivated basement faults associated with recent induced seismicity.
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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 | 0.000 | 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) | 0.002 | 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".