Regional electrical resistivity structure of the southern Canadian Cordillera and its physical interpretation
Bibliographic record
Abstract
The regional geoelectric crustal structure of the southern and central Canadian Cordillera of western Canada is interpreted from the inversion of magnetotelluric data along five profiles crossing the physiographic morphogeological belts, with emphasis on the Intermontane and Omineca Belts. Decomposition of the tensor impedance response estimates demonstrates that large‐scale regional structures can be reasonably approximated along each profile as two‐dimensional, with dominant geoelectric strikes of either −30° or +15°, depending on profile location. These profile‐specific strike directions are consistent with a local clockwise rotation of crustal structures in the southern Intermontane and Omineca Belts suggested by others based on paleomagnetic data and palinspastic reconstructions. Comparing the resistivity models derived from two‐dimensional inversions of the distortion‐corrected data along each profile allows us to construct an orogen‐scale three‐dimensional resistivity model for southern British Columbia. Generally, the model shows a resistive upper crust overlying a conductive lower crust. The resistivity of the lower crust beneath the Intermontane Belt is independent of latitude and is similar for all profiles. In stark contrast, a 2 orders of magnitude variation in lower crustal resistivity is observed along strike in the Omineca Belt, with higher conductivities to the south in the region of Eocene extension and lower conductivities to the north in the unextended part of the belt. Such spatial association has noteworthy implications for the cause of lower crustal resistivity in active, or recently active, young regions. Our preferred interpretation of the observed lower crustal resistivities with other geophysical data is in terms of fluids, with brines dominating for the most part but partial melt possible at the base of the crust in specific localities. We attribute the along‐strike variation in the Omineca Belt mostly to variation in fluid content and interconnectivity, with the lowermost crust of the southern Omineca Belt being partially molten. This physical state difference is a consequence of degree of extension and implies that mantle‐derived fluids are important for lower crustal resistivity.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".