Localized Backarc Extension in an Overall Compressional Setting During the Assembly of Nuna: Geochemical and Isotopic Evidence From Orosirian (1883–1848 Ma) Mafic Magmatism of the Aillik Group, Labrador, Canada
Bibliographic record
Abstract
Abstract Bimodal volcanism occurs in a range of extensional environments that are characterized by distinctive but overlapping, lithogeochemical and isotopic signatures and lithological assemblages. Where basaltic magmatism is associated with ferroan (A‐type) rhyolites, it is typically the lithogeochemistry and isotopic systematics of the basaltic rocks that are the most beneficial in constraining the tectonic evolution. This study presents geochemical and isotopic data from mafic volcanic rocks of the bimodal Aillik Group, that formed during the assembly of the Paleoproterozoic supercontinent Nuna. Lithogeochemical signatures define two suites. Suite 1 samples have N‐MORB (Normal‐Mid‐Ocean Ridge Basalt) chemical affinities such as flat HREE, and smooth but flat LREE and have εNd ( t = 1860 Ma) values between +2.8 and +4.8. Suite 2 samples typically have compositions between N‐MORB and IAT (Island Arc Tholeiites) basalts, with variable REE patterns ranging from IAT to OIB (Ocean Island Basalt). The basalts display moderately developed subduction zone signatures, such as negative Nb and Ti, and have εNd ( t = 1860 Ma) ranging from −3.4 to +2.2. Geochemical variability within the Aillik Group mafic rocks is explained by processes active in arc settings and involves mixing between depleted mantle components with variable contributions from crustal and subducted‐slab sources. Coupled with field evidence, the geochemical and isotopic data support emplacement of the basalt in an extensional, backarc basin setting. This backarc basin formed due to localized extension during Nuna assembly. The Makkovik Province preserves a complex orogen characterized by multiple diachronous, compressional, and extensional events along a long‐lived active margin of the Archean North Atlantic Craton.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".