Abstract: Field relationships, petrology, and age of granitic and syenitic plutons in the Antigonish Highlands, Nova Scotia
Bibliographic record
Abstract
The Antigonish Highlands of Nova Scotia have characteristic features of Avalonia, including Neoproterozoic arc-related volcanic and plutonic rocks and Cambrian-Silurian cover sequences. Also present in the southern part of the highlands are scattered plutons previously inferred to be of DevonianCarboniferous age. Although contacts are not exposed, these plutons were interpreted to have intruded Neoproterozoic and Silurian volcanic and sedimentary rocks. This project focuses on the field relationships, petrology, age, and tectonic implications of these plutons. One of the plutons, Hunters Lake, consists of tonalite and minor granodiorite, and is likely to be closely related to quartz diorite of the Neoproterozoic (based on previously determined K-Ar ages) Eden Lake Complex. Such an interpretation is consistent with the lack of contact metamorphism in the surrounding fossiliferous Silurian rocks. Preliminary geochemical analyses show these rocks to be calc-alkaline and formed in a subduction zone setting. The other plutons consist of varying proportions of granitic and syenitic rocks. The granitic rocks include distinctive alkali-feldspar granite and syenogranite with quartz eyes and interstitial granophyric texture indicative of shallow emplacement. Although predominantly subalkalic, samples from three of the plutons (Barneys River, McGraths, and Leadbetter) have chemical characteristics of within-plate granitoid rocks, whereas a fourth pluton, Gunn Lake, has a volcanic-arc granite composition. These plutons overall show fractionated compositions, including high Si (SiO2>71%), K, Ba, Rb, and Th, and depletion in elements such as P, Ca, and Mg. The predominantly syenitic rocks in the Brora Lake area contain aegirine and in some samples riebeckite, indicative of peralkaline composition. An additional pluton (Haggarts Lake), previously mapped as Neoproterozoic diorite, is also of syenitic composition and related to the Brora Lake pluton. Geochemistry confirms that these plutons are peralkaline and have high concentrations of K, Na, P, Ti, and Fe with an intermediate range in silica content (54–64% SiO2). Tectonic discrimination diagrams indicate a within-plate setting for these plutons. An alkali-feldspar granite sample from the Gunn Lake Pluton yielded a preliminary U-Pb (zircon) upper intercept age of about 605 Ma, consistent with the concordant U-Pb (zircon) age of 610 ± 3 Ma reported previously for the petrographically
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".