Mesoproterozoic deep K-magmatism recorded in a megacryst- and xenolith-bearing minette dyke, western Grenville Province
Bibliographic record
Abstract
The 1.07 Ga Rivard minette dyke transported thousands of exotic (xenoliths) and cogenetic (cognate nodules) clasts from deep lithospheric levels of the Grenville Province. Nodules related to the clinopyroxene- and biotite-phyric host consist of megacrystic clinopyroxene and K-feldspar and mica-rich pyroxenite. Clinopyroxene megacrysts record high-pressure and high-temperature crystallization, crystal recycling, or magma mixing, whereas Ba-rich K-feldspar megacryst possibly represent near-solidus phenocrysts crystallized from evolved K-rich magmas. Mica-pyroxenite xenoliths are interpreted as products of magma mixing or infiltration of K-rich melt in pyroxene cumulate. Partial replacement of pyroxenes by strained phlogopite attests to mica crystallization before or during plastic deformation and prior to xenolith incorporation in the minette. The minette is mafic, ultrapotassic, and enriched in large-ion lithophile elements and light rare-earth elements. It experienced limited fractionation and crustal contamination but has been exposed to magma mixing. High K, La, and Cr contents suggest partial melting of a K-metasomatized mantle source. The Rivard minette shares the age, mineralogy, and chemistry with the 1.091.07 Ga KensingtonSkootamatta potassic alkaline suite and forms part of a common K-rich magmatic event taking its source in an enriched mantle. Source heterogeneity, conditions of partial melting, crystal fractionation, magma mixing, and crustal contamination all contributed, to various extents, to the complex chemistry of the K-rich intrusions of the KensingtonSkootamatta suite. Collectively, this suite records extensive and diverse magmatic batches derived from partial melting of a mantle metasomatized during subduction events prior to emplacement.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".