STRONTIUM IN FELDSPARS OF HIGH-K PROTEROZOIC IGNEOUS ROCKS OF THE ROBITAILLE SUITE, BUCKINGHAM, QUEBEC
Bibliographic record
Abstract
Near Buckingham, Quebec, Sr-, K-rich rocks exposed in small, Mesoproterozoic, volcano-plutonic bodies of the Robitaille suite overlie or intrude the Grenville metasedimentary sequence and are cut by Neoproterozoic diabase dykes. They may represent near-surface equivalents of the Mont Laurier – Marmora alkaline plutons. The rocks includes latite and alkali-feldspar trachyte, lamprophyres (kersantite and minette), monzodiorite and alkali-feldspar syenite. Ultrapotassic compositions are common. The complexes, up to 2.7 km long and 1.0 km wide, are partly fringed with aureoles of Sr-rich, dolomitized calcitic marble. In 20 samples from three igneous complexes, Sr (up to 3960 ppm) is present in celestine (very rare), barite (rare), fluorapatite and calcite, but feldspars are the main hosts. K-feldspar without plagioclase occurs in samples with K 2 O/Na 2 O > 15 (weight ratio), and K-feldspar + plagioclase in samples with a lower ratio. Individual grains of plagioclase in the groundmass of lamprophyre are unzoned, but distinct ranges of An content are found in grains from restricted areas within a single polished thin section. The amount of Sr increases linearly with An content, from near zero at end-member albite to 1.0–2.6 wt% SrO at An 40 . In one sample of latite, Sr peaked at An 30 . Variation of Sr within a single sample is due to both differentiation (mainly by crystallization of sanidine) and equilibrium factors (such as temperature and An content). Clustering of point compositions on An – wt% diagrams for individual samples may reflect periods of volcanicity, separated by quiescent intervals, as differentiation evolved continuously in the parent magma-chamber. Barium is low, but can be correlated with Sr in one kersantite sample. The distribution of Sr between contiguous K-feldspar and plagioclase grains is governed by disequilibrium factors at low An content. For feldspar pairs, Sr preferentially enters more calcic plagioclase (An > ca. 10), but K-feldspar where plagioclase is more sodic (An ca. 10).
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".