U–Pb zircon ages and field relationships of Archean basement and Proterozoic intrusions, south-central Wopmay Orogen, NWT: implications for tectonic assignments
Bibliographic record
Abstract
New field and U–Pb zircon data from the south-central Wopmay Orogen (south of 65°N) establish crystallization ages of basement and plutonic phases and bring to the forefront questions on the architecture of the orogen. The complex and extensive >3300–2575 Ma basement domain was derived from the adjacent Slave craton. Paleoproterozoic supracrustal rocks, dominated by an extensive pelitic–psammitic sequence with basal arenite, conglomerate, and carbonate, unconformably overlie this basement. Pre- to post-kinematic Paleoproterozoic plutons intrude both basement and overlying strata and crystallized at 1877, 1867–1862, and 1858–1850 Ma. The first pulse of plutonism constrains an early generation of metamorphism and deformation to younger than 1877 Ma and is corroborated by metamorphic zircon in Archean basement. The interval from 1867 to 1862 Ma brackets ductile deformation in granite and granodiorite intrusions; although corresponding structure in the metasedimentary strata is equivocal. Post-kinematic ca. 1858–1850 Ma plutons were coeval with localized high-grade metamorphism and concomitant recrystallization of Archean basement. The absence of older (>1880 Ma) phases of the Hepburn intrusive suite in south-central Wopmay Orogen demonstrates a previously unrecognized north–south plutonic dichotomy and that the historical assignment of Calderian metamorphism to ca. 1885 Ma may be too old. The designation of part of the area to a klippe of Hottah terrane is not compatible with field and zircon age data which shows that basement and the overlying strata can be tied directly to the Slave craton. The study raises questions regarding the tectonic relationship between the Hottah terrane and Slave craton.
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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 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".