Variable unroofing in the western Superior Province - metamorphic evidence and possible origin
Bibliographic record
Abstract
Western Superior Lithoprobe seismic-reflection line 1 exhibits a broad region of northward-dipping reflectors in the Uchi subprovince, which gives way to southward-dipping reflectors farther north in the Berens River sub province. Mafic metavolcanic rocks across the region of northward-dipping reflectors exhibit a decline in metamorphic pressure, from pressures of 6 kbar (1 kbar = 100 MPa) in the south to only 2 kbar 80 km to the north. This indicates that the southern edge of the Uchi subprovince has undergone significantly more unroofing than regions farther north. The differential unroofing is not consistent with a doubly vergent thrusting origin for the northward- and southward-dipping reflector pattern. It could result from a crustal-scale synform, of which the region of northward-dipping reflectors would make up the southern limb. Metamorphic pressures from samples off the seismic line, however, provide only limited support for a regional synform, and suggest that much of the pressure variation may result from deformation associated with motion on late faults that are widespread in the western Superior Province. These faults occur in a WNW-striking set with dextral offsets and an ENE-striking set with sinistral offsets. They could result from northsouth compression and eastwest extension, provided the faults have rotated towards the eastwest direction during deformation. Regional tilting and (or) jostling of crustal blocks is attributed to deformation associated with the fault rotation. Motion on the faults and the associated deformation of intervening fault blocks may be important contributors to the present crustal architecture of the western Superior Province, including the surface distribution and form of the greenstone belts.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| 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) | 0.002 | 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".