A U–Pb geochronological review of the Proterozoic history of the eastern Grenville Province
Bibliographic record
Abstract
The geological evolution of the eastern Grenville Province can be subdivided into three stages. During the first stage, namely pre-Labradorian (> 1710 Ma) and Labradorian (17101600 Ma) events, a continental-marginal basin was created and subsequently destroyed during accretion of a magmatic arc formed over a south-dipping subduction zone. Subduction was short-lived and arrested, leading to a passive continental margin. The second stage addresses events between 1600 and 1230 Ma. The passive margin lasted until 1520 Ma, following which a continental-margin arc was constructed during Pinwarian (15201460 Ma) orogenesis. Elsonian (14601230 Ma) distal-inboard, mafic and anorthositic magmatism, decreasing in age northward, is explained by funnelled flat subduction, possibly associated with an overridden spreading centre. As the leading edge of the lower plate advanced, it was forced beneath the Paleoproterozoic Torngat orogen root between the Archean Superior and North Atlantic cratons, achieving its limit of penetration by 1290 Ma. Static north-northeast-trending rifting then ensued, with mafic magmatism flanked by felsic products to the north and south. Far-field orogenic effects heralded the third stage, lasting from 1230 to 955 Ma. Until 1180 Ma, the eastern Grenville Province was under the distal, mild influence of Elzevirian orogenesis. From 1180 to 1120 Ma, mafic and anorthositic magmatism occurred, attributed to back-arc tectonism inboard of a post-Elzevirian Laurentian margin. Quiescence then prevailed until Grenvillian (1080980 Ma) continentcontinent collision. Grenvillian orogenesis peaked in different places at different times as thrusting released stress, thereby precipitating its shift elsewhere (pressure-point orogenesis). High-grade metamorphism, thrusting and minor magmatism characterized the Exterior Thrust Zone, in contrast to voluminous magmatism in the Interior Magmatic Belt. Following final deformation, early posttectonic anorthositicalkalicmafic magmatism (985975 Ma) and late posttectonic monzoniticsyenitegranite magmatism (975955 Ma) brought the active geological evolution of this region to a close.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".