Reactivation of the Eastern Highlands Shear Zone, Cape Breton Island, Appalachian Orogen
Bibliographic record
Abstract
The Eastern Highlands shear zone (EHSZ), in the Cape Breton Island portion of Appalachian Orogen, records two ductile deformation events (D1 and D2) from Early Silurian to Late Devonian. The Devonian is a key period for the economic endowment of the orogen during which intrusion-related mineralization may be associated with active and/or reactivated regional shear zones. The EHSZ is, therefore, a key structure to characterize shear zone reactivation and assess how this may have localized ore-bearing intrusive rocks. To accomplish this, we have first focused on linking local deformation events to the regional kinematic framework. New U-Pb geochronology of zircon from de-formed specimens provide timing constraints on the two deformation events of the EHSZ. A rhyolite specimen with D1 fabrics and a granite dyke specimen affected by D2 deformation, both within the EHSZ, yielded weighted mean 206Pb/238U crystallization ages of 424 ± 4 Ma and 372 ± 4 Ma, respectively (2-sigma error). In addition, two foliated quartz-diorite specimens and a post-tectonic pegmatite specimen from the Chéticamp gneiss, west of the EHSZ, yielded weighted mean crystallization ages of 428 ± 9 Ma, 390 ± 8 Ma, and 391 ± 8 Ma, respectively. These new data constrain the EHSZ D1 to between ca. 424 and 390 Ma, likely during the Acadian Orogeny. The EHSZ was then reactivated (D2) after 372 Ma, which we attribute to the Neoacadian Orogeny. Considering the orientations and kinematics of the Neoacadian suture and the EHSZ, we interpret that the EHSZ was reactivated in a transpression-dominated environment.
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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 | 0.001 |
| 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".