EARLY MESOZOIC ALKALINE MAFIC DYKES, SOUTHWESTERN NOVA SCOTIA,
Bibliographic record
Abstract
Dykes of lamprophyre and alkaline olivine diabase cut the Cambro-Ordovician Goldenville Formation and the Carboniferous Wedgeport Pluton near Plymouth, southwestern Nova Scotia. 40Ar/39Ar geochronology yielded hornblende–biotite ages ranging between 231 ± 3 and 222 ± 3 Ma (mean 227 Ma) for the lamprophyres, and biotite ages of 209 ± 6 and 203 ± 15 Ma for the olivine diabase. Minerals present in the dykes include olivine (Fo83), augite with a rim of titanaugite, kaersutite and titaniferous phlogopite. The whole-rock composition of both the lamprophyre and olivine diabase shows greater LILE and HFSE enrichment in the lamprophyres, but the relative abundances of these elements are remarkably similar in the two rock types, suggesting that they are comagmatic. Values of «Nd (~+4) and «Sr (~+5) are much more primitive than values for the widespread early Jurassic tholeiites. Pb isotope compositions for the lamprophyres fall near the Northern Hemisphere Reference Line; those of the olivine diabase are intermediate between the lamprophyres and more radiogenic Pb compositions typical of the Triassic alkaline dykes at Seabrook, New Hampshire, and the early Jurassic tholeiites; they may have experienced some contamination in the lower crust. The lamprophyres resemble, in age and chemical composition, other alkaline rocks of the Coastal New England province. The olivine diabases, apparently synchronous with the main Eastern North American tholeiites, represent renewed partial melting of the same mantle source, triggered by the thermal effect of the regional tholeiitic magma.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".