New constraints on the timing and nature of metamorphism in the eastern Meguma terrane, Nova Scotia, Canada
Bibliographic record
Abstract
The Meguma terrane in Nova Scotia consists mainly of Cambrian to Ordovician metasedimentary rocks intruded by abundant peraluminous granite, granodiorite, and minor diorite–tonalite–plutons between ca. 380 and 360 Ma. The metasedimentary rocks were variably metamorphosed to greenschist- to amphibolite-facies during the Early Devonian. In the eastern Meguma terrane, the regional M1 chlorite- and biotite-zone assemblages are overprinted by two types of high-temperature low-pressure M2 metamorphism. In contact aureoles around plutons the regional M1 assemblages are overprinted by cordierite- and andalusite-bearing M2 contact metamorphic assemblages, and away from plutons chlorite-bearing, (or biotite-bearing) regional M1 assemblages are overprinted by staurolite-, garnet-, and (or) cordierite-bearing M2 regional assemblages that represent metamorphism driven by a regional elevated thermal gradient. The interpreted metamorphic conditions in the eastern Meguma terrane range from ca. 480–550 °C and pressures below 2.5 kbar up to 550–650 °C with pressures between 4 and 5 kbar. Based on a new garnet Lu–Hf age, regional metamorphism was ongoing at ca. 372 Ma, hence broadly coeval with pluton emplacement. Metamorphism and pluton emplacement took place in a largely transpressional tectonic setting during the collision of the Meguma terrane with Avalonia. After pluton emplacement, peak metamorphic assemblages were variably overprinted with retrograde chlorite and sericite M3 assemblages while deformation continued. Regional structures were transposed into a composite transposition foliation as a result of continued motion along the terrane-bounding Minas Fault Zone and associated ductile shear zones.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".