The metamorphic record of crustal assembly in the Paleoproterozoic Southeastern Churchill Province, Trans-Hudson Orogen, Canada
Bibliographic record
Abstract
Dating the onset of the continental collision and amalgamation of crustal blocks is at the basis of the reconnaissance of orogenic cycles and yields time constraints for the estimate of rates of accretionary processes over the last 4.5 Gyrs. The Paleoproterozoic Southeastern Churchill Province (SECP) represents the easternmost branch of the Trans-Hudson Orogen, squeezed between the Superior and North Atlantic Cratons (NAC). It comprises a collage of Archean to Paleoproterozoic crustal blocks (Core Zone), and two transpressive orogenic belts (New Quebec and Torngat Orogens), for which crustal amalgamation and associated collisional events are largely undated. We apply a multi-chronometer approach coupled with trace elements geochemistry on supracrustal sequences from the granulitic Tasiuyak Complex accretionary prism and the occidental margin of the NAC (upper plate) to estimate the timing of prograde, peak and retrograde metamorphism in the core of the Torngat Orogen. Our results yield to prograde garnet growth at 1885 ± 12 Ma (Lu-Hf), peritectic prograde monazite growth at 1873 ± 5 Ma (U-Pb), retrograde zircon growth during melt crystallization at 1848 ± 12 Ma, and rutile closure during slow exhumation at 1705 ± 5 Ma in the Tasiuyak Complex. Garnet from the NAC are dated at 2567 ± 4.4 Ma (Lu-Hf) and suggest that the granulite facies metamorphism in the NAC margin largely predates the Torngat Orogeny. We integrate the metamorphic record throughout the SECP to decipher its Paleoproterozoic tectonometamorphic evolution and propose a sequential collisional evolution from ~1.9 to 1.8 Ga.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".