A Mainly Crustal Origin for Tonalitic Granitoid Rocks, Superior Province, Canada: Implications for Late Archean Tectonomagmatic Processes
Bibliographic record
Abstract
Abstract The central Wabigoon subprovince of the Superior Province, like most plutonic domains within Archean cratons, is dominated by granitoid rocks of the tonalite–trondhjemite–granodiorite (TTG) series. Heterogeneous <2·83–2·74 Ga tonalite gneisses and foliated tonalite to granodiorite units, emplaced at 2·722–2·709 Ga, exhibit initial εNd values (–3·1 to +3·3) indicative of variable input from light rare earth element enriched older (3·2–3·4 Ga) crustal materials. Their δ18O (VSMOW) range (+7·1 to +8·9‰), which overlaps closely that of average upper Superior Province crust, indicates input from high-18O crustal materials. The preferred petrogenetic model for Wabigoon tonalitic rocks involves partial melting of overthickened amphibolite-dominated lower-crustal materials within a Cordilleran-type arc. Assimilation of >2·74 Ga tonalite gneiss crust by younger tonalite magmas was probably an important process. Unlike the model of TTGs representing direct partial melts of subducting slabs in an arc setting, this model requires no direct tie to subduction. Careful re-evaluation of the TTG classification is required for it can mistakingly ‘pigeon-hole’ temporally and genetically unrelated rocks and perhaps assume an incorrect petrogenetic or tectonic model. An important role of crustal recycling processes in central Wabigoon tonalite petrogenesis is in keeping with evidence that supports substantial rates of continental recycling as far back as the earliest Archean.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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".