Age and geochemistry of basement complexes in the south-central New Québec Orogen: Archean history, terrane correlations, and Paleoproterozoic reactivation
Bibliographic record
Abstract
U–Pb geochronological, geochemical, and Sm–Nd isotopic data from metaplutonic rocks in the south-central New Québec Orogen (NQO) provide new insights into the long-term tectono-magmatic evolution of western Labrador. Basement units are divided into two complexes—the Snelgrove Lake Basement Complex (SLBC), exposed beneath sedimentary rocks of the Labrador Trough, and the Griffis Complex—separated from each other by a Hudsonian-aged ductile shear zone. The oldest rocks in both complexes are variably metamorphosed tonalite to granodiorite with whole-rock compositions similar to Archean tonalite–trondhjemite–granodiorite (TTG) suites (sensu lato), and εNd i = 1.69 to −4.83, indicating formation by medium- to high-pressure partial melting of meta-basalt with variable assimilation of older continental crust. Zircon U–Pb geochronological results indicate TTG magmatism at 2670.8 ± 4.6 and 2677 ± 12 Ma followed by broadly coeval metamorphism at 2620 ± 17 and 2594 ± 13 Ma, respectively, and support previous suggestions that NQO basement originated as part of the Superior craton. Proterozoic magmatism affected both domains but at different times. In the SLBC, the 2198.23 ± 0.89 Ma Snelgrove granite exhibits elevated REE contents, strong high-field-strength element enrichment, and negative εNd i (−4.64), suggesting formation by high-temperature, low-pressure crustal melting interpreted to represent an early phase of rifting in the Labrador Trough. Equivalent magmatism was not found in the Griffis Complex. Instead, deformed peraluminous leucogranite dykes, intruded at 1637.47 ± 1.1 and 1633.3 ± 5.8 Ma, and with εNd i = −12, reveal a previously unrecognized phase of crustal melting and deformation related to the Labradorian orogeny farther south. These data highlight a more complex history for the south-central NQO than established by previous reconnaissance-scale work and underscore the need for additional geoscience data to better constrain the tectonic evolution of the region.
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 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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".