Trans-crustal geophysical responses beneath the supergiant Timmins-Porcupine orogenic gold camp, Canada
Bibliographic record
Abstract
A new 80-site magnetotelluric (MT) survey, integrated with reprocessed seismic reflection profiles, across the supergiant Timmins-Porcupine gold camp of the Abitibi greenstone belt (AGB) was conducted to investigate the architecture of crustal-scale structures. Resistivity sections derived from 3-D MT inversions reveal a major 40 km by 20 km sub-horizontal 500-1000 S conductor north of the Porcupine Destor fault zone at 5–10 km depth. A horizontal component of this conductor, attributed to a deeply buried >2687 Ma graphitic argillaceous unit at the base of Porcupine assemblage, strikes east-west parallel to the Pipestone fault zone. A second steeply-dipping component strikes northwest-southeast parallel to the Buskegau River fault. This conductor correlates spatially with lateral breaks in seismic reflectors and velocity models in the upper, middle, and lower crust, and provides evidence of a crustal-scale suture which also resulted in imbrication of <2698 Ma metasedimentary rocks onto the southern AGB. Enhanced conductivity and spatially complex electrical structure of the crust to the north of the Porcupine Destor fault zone reflects the asymmetric distribution of metasedimentary packages, second- and third-order bounding structures, and gold mineralization. The MT resistivity models also resolve an upper crustal conductor located 10 km south of the surface trace of the Porcupine Destor fault zone, providing support for a south-dipping crustal fault. Breaks in seismic reflectors underlying this conductor provide additional evidence of sub-vertical structures extending through the middle crust, postdating post-tectonic collapse or orogen-parallel ductile flow at ∼2660-2590 Ma, and consistent with late strike-slip deformation.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".