Petrology, age and tectonic setting of the Gunshot Brook pluton, Eastern Cobequid Highlands, Nova Scotia
Bibliographic record
Abstract
The goal of this project was to provide new information about field relations, petrology, age, and tectonic significance of the enigmatic Gunshot Brook pluton in the eastern Cobequid Highlands of northern mainland Nova Scotia. Field mapping showed that pluton intruded the ca. 760-735 Ma Mount Ephraim plutonic suite on its southern margin and the >735 Ma Dalhousie Mountain Formation on its western, northern and eastern margins. Petrographic study revealed that the pluton consists mainly of granodiorite gradational to monzogranite and tonalite, with minor co-mingled dioritic rocks, all cut by mafic and felsic dykes. Whole-rock chemical data from about 40 samples display trends consistent with a comagmatic relationship among the tonalitic, granodioritic, and monzogranitic rocks, and a compositional gap between them and the mingled dioritic rocks. They are calc-alkalic and likely formed in a continental margin subduction zone together with the associated dioritic rocks. U-Pb zircon ages of 630.6 ± 2.7 Ma and 638.6 ± 2.5 Ma for granodiorite samples from the northern and southern parts of the pluton are consistent with petrological similarities which suggest that the cross-cutting Millsville fault does not have significant offset. Granitic and dioritic rocks from the southeastern part of the pluton have chemical characteristics which indicate that they are part of the Mount Ephraim plutonic suite rather than Gunshot Brook pluton, resulting in revision to the mapped extent of the Gunshot Brook pluton. Because these plutons differ in age from the ca. 620-600 Ma plutons of the Jeffers and Bass River blocks of the Cobequid Highlands, the Gunshot Brook pluton, Mount Ephraim plutonic suite, and ca. 735 Ma Six Mile Brook pluton, together with their host rocks, are assigned to a separate Mount Ephraim block, of as yet uncertain relation to the rest of the highlands, and to Avaloniain in general.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".