New U-Pb (zircon and monazite) ages and Sm-Nd isotopic data from granitoid plutons in the Aspy and Bras d'Or terranes of Cape Breton Island, Nova Scotia: implications for tectonic evolution and mineralization potential
Bibliographic record
Abstract
Granitoid plutons are widespread in the Ganderian Aspy and Bras d'Or terranes of Cape Breton Island and are diverse in composition, isotopic characteristics, and tectonic affinity. This study presents new U-Pb zircon ages from 10 previously undated plutons or their host rocks in the two terranes. The results range from Neoproterozoic (ca. 575 and 560 Ma in the Big Hill granodiorite and Price Point Formation), through Cambrian (ca. 515 and 510 Ma in Kellys Mountain diorite and granodiorite), Silurian (ca. 436 Ma in the Gillis Brook diorite, Gillanders Mountain granite, and ca. 420 Ma in the Leonard McLeod syenogranite), to Devonian (ca. 379 and 363 Ma in the Park Spur granite and Margaree pluton). Two samples were dated using U-Pb in monazite but the results for those were inconclusive and require further work. Overall the U-Pb zircon ages for samples presented here along with other recent work show a more complex magmatic history in the Bras d'Or and Aspy terranes than previously documented, and in particular more widespread Silurian magmatism. Epsilon-Nd data from this study shows that Bras d'Or and Aspy terrane rocks have negative epsilon-Nd values characteristic of Ganderia. These results show Aspy and Bras D'Or terranes likely share similar basement rocks, and are both isotopically distinct from Avalonia, which has mainly positive epsilon-Nd, and is represented in Cape Breton by the Mira terrane.
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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 | 0.000 | 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) | 0.001 | 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".