Proterozoic anorthosite–granite Nain batholith: structure and intrusion processes in an active lithosphere-scale fault zone, northern Labrador
Bibliographic record
Abstract
We present field evidence of the structure and evolution of a typical Proterozoic massif-type anorthosite. The anorthosite forms a batholith composed of numerous plutons and ring complexes intruded episodically in two main sequences, each producing anorthositic rocks and monzonite–ferrodiorite followed by granite. The batholith is located where a lithosphere-scale fault zone, ∼50 km wide and extending over 1000 km from Greenland to Labrador, intersected an older continental suture. Intermittent episodes of mainly sinistral transtension along this Gardar – Voisey’s Bay fault zone were associated with the generation of a number of pulses of magmatism and controlled the rise of magmas to middle and upper crustal levels between ∼1363 and 1289 Ma. Both the large- and small-scale structures and magma intrusion processes are similar to those of many cordilleran batholiths, with tabular plutons associated with ring dykes emplaced by cauldron subsidence, and basin-shaped plutons associated with cone sheets. These structures are well known in subvolcanic situations but little known at the mid-crustal depth of the Nain batholith. The location of these structures within the batholith was controlled by intersecting, externally generated faults and shear zones. We conclude that this typical massif-type anorthosite is an intracratonic structural equivalent of cordilleran batholiths of continental margins.
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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 | 0.001 |
| 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".