A Tall Tale of a Tiny Pluton: The L’Enfer Norite, Grenville Province, Québec
Bibliographic record
Abstract
Abstract We present new field observations and mineral and whole-rock geochemical data for the L’Enfer norite, a small pluton in the central Grenville Province of Québec. Although tiny, its plagioclase-rich and noritic character suggested that it might hold clues (possible parental magma?) to the origin of closely associated andesine anorthosites in this part of Québec. The pluton is characterized by spectacular coarse-grained diabasic textures and varies from relatively massive to locally layered varieties. Both coarse- and medium-grained types occur and may be present together in some outcrops. Rare occurrences of snowflake-textured plagioclase are also present. The mafic mineralogy is dominated by orthopyroxene and Fe-Ti oxides (ilmenite and magnetite) with minor clinopyroxene, amphibole (Ti-pargasite), and Ti-rich biotite. Olivine occurs in one of the norites and in a single occurrence of an ultramafic rock that is also enriched in Fe-Ti oxides. Plagioclase compositions range from An32 to An48, but can be divided into two groups on the basis of texture: in one subset of samples, the plagioclase contains exsolution lamellae of orthoclase (i.e., antiperthitic), whereas plagioclase in the remaining samples lacks such lamellae and has not exsolved. Despite these textural contrasts, whole-rock compositions of the two groups are similar. Surprisingly, the compositions of pyroxene, biotite, and ilmenite reveal two non-overlapping compositional groups that correlate with those defined by plagioclase texture. Specifically, mafic minerals in the group with unexsolved plagioclase are consistently enriched in minor elements compared to those in the group with antiperthitic plagioclase. We interpret these contrasts to reflect differences in cooling rate for at least two injections of noritic magma. Moreover, the snowflake plagioclase grains are consistent with some degree of undercooling and supersaturation brought about by magma mixing. Although the norite shares some mineralogical and geochemical features with nearby anorthosites, it does not appear to represent a viable parent magma, primarily due to a pronounced difference in Fe-Ti oxide assemblage (hemo-ilmenite in the anorthosites versus ilmenite + magnetite in L’Enfer).
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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 | 0.001 | 0.001 |
| 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) | 0.005 | 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".