The geology of Nuvvuagittuq greenstone belt and its implications for the early earth's evolution
Bibliographic record
Abstract
The Nuvvuagittuq greenstone belt is an Eoarchean/Hadean succession preserved along the eastern coast of Hudson Bay in the Northeastern Superior Province, Quebec, Canada. It is essentially composed of three major lithological units: 1) mafic cummingtonite-amphibolite, known as the "faux-amphibolite", which is the dominant lithology of the belt, 2) ultramafic and mafic sills that intrude the faux-amphibolite, and 3) chemical sedimentary rocks comprising a banded iron formation (BIF) and a silica-formation. The faux-amphibolite has a basaltic to andesitic composition. It is composed of variable proportions of cummingtonite + biotite + quartz, ± plagioclase ± garnet ± anthophyllite ± cordierite and ranges from cummingtonite amphibolite to garnet-biotite schist. Some rocks from the Nuvvuagittuq greenstone belt have lower 142Nd /144Nd ratios than the terrestrial standard (epsilon142Nd = -0.07 to -0.15). The 142Nd/144Nd ratios for the faux-amphibolite correlate positively with their Sm/Nd ratios and produce a 146Sm-142Nd isochron with an age of 4280 +53 –81 million years. The 4.28 Ga faux-amphibolite is intruded by highly deformed gabbro sills yielding a 147Sm-143Nd isochron with a slope corresponding to an age of 4023 ± 110 Ma. The Nuvvuagittuq greenstone belt also comprises 3.8 Ga felsic bands and is surrounded by 3.66 Ga tonalite interpreted to have been produced by the melting of the older mafic faux-amphibolite. The Nuvvuagittuq greenstone belt thus represents an Eoarchean/Hadean crustal section comprising the oldest rocks preserved on Earth. The 4.28 Ga faux-amphibolite is divided into a high-Ti group and a low-Ti group with co-genetic ultramafic sills and separated by a BIF/silica-formation. At the base of the sequence, the high-Ti faux-amphibolite is basaltic in composition and has "tholeitic" affinities. The low-Ti faux-amphibolite above the BIF exhibits a wider range of composition from basalti
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".