Petrology and Isotopic Composition of a Grenvillian Basement Fragment in the Northern Appalachian Orogen: Blair River Inlier, Nova Scotia, Canada
Bibliographic record
Abstract
Mesoproterozoic metaplutonic rocks in northern Cape Breton Island, Nova Scotia, occur in a tectonic inlier within the Appalachian orogen. Although they have been multiply metamorphosed and variably deformed, the petrology and geochemistry of these rocks provide insight into the tectonomagmatic evolution of easternmost Laurentia. Anorthosite, syenite, and granitoid plutons (1100–980 Ma) intruded the Sailor Brook and Polletts Cove River gneisses. New Nd isotopic data are presented from a biotite-rich part of the Sailor Brook gneiss (εNdi = −0·7), two anorthosite samples (εNdi = +2·1 and +2·8), and a charnockite unit (εNdi = −0·4). New U–Pb zircon data from the anorthosite yield 207Pb/206Pb ages between 975 and 1095 Ma. Disrupted U–Pb systematics preclude a unique age interpretation, but the ∼1095 Ma single-grain date is a minimum age for the anorthosite. Field relations, major and trace-element geochemistry, and isotopic characteristics indicate that the anorthosite and charnockite were probably coexisting melts, but not differentiates of a single parent magma. The lithological and chemical characteristics of the Lowland Brook Syenite are similar to those of a contemporaneous belt of ultrapotassic plutons in the southern Grenville Province, and both have the chemical characteristics of certain modern continental-margin arc magmas. These data indicate that the Mesoproterozoic units in the Blair River inlier were juvenile crustal additions to eastern Laurentia during Grenville-related orogenic events.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 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) | 0.002 | 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".