Crustal development at the pre-Grenvillian Laurentian margin: a record from contrasting geochemistry of mafic and ultramafic orthogneisses in the Chochocouane River area, Quebec
Bibliographic record
Abstract
Mafic and ultramafic orthogneisses from the western Grenville Province of Quebec adjacent to the Archean Superior Province (Canada) display geochemical characteristics that highlight processes that shaped the pre-Grenvillian Laurentian margin through late Archean to Mesoproterozoic time. Group I mafic and ultramafic granulites of the Parautochthonous Belt compositions overlap Archean Abitibi metavolcanic rocks (komatiites to Fe-rich andesites) supporting their autochthonous character. Limited variation of incompatible trace-element ratios with increasing differentiation suggests minimal sialic crust assimilation during petrogenesis and probable formation in an oceanic setting. Group II mafic tholeiites occur within both the Parautochthonous Belt and the Allochthonous Polycyclic Belt. Their compositions differ significantly from those of Archean rocks but overlap those of Proterozoic and modern continental tholeiites. Group III mafic calc-alkaline amphibolites, predominantly in the Allochthonous Polycyclic Belt, display chemical characteristics expected of magma derivation from subducted oceanic crust. In contrast to group I Archean meta-igneous rocks metamorphosed during the Kenoran orogeny, group III rocks do not record an early phase of large-ion lithophile element (LILE) metasomatism and granulite-facies metamorphism. As such, their emplacement is interpreted to postdate the Archean Kenoran metamorphism and to be Proterozoic in age. Group I rocks reflect an Archaean ensimatic greenstone belt environment; group II tholeiites reflect a Proterozoic continental rift environment; and group III rocks reflect a subduction-related source, possibly related to Andean-style, calc-alkaline magmatism.
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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 | 0.002 | 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 | 0.000 |
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".