Reconnaissance U-Pb SHRIMP geochronology and Sm-Nd isotope analyses from the Tehery-Wager Bay gneiss domain, western Churchill Province, Nunavut
Bibliographic record
Abstract
U-Pb SHRIMP, Sm-Nd isotopic and chemical analyses are presented for archived samples from the Tehery-Wager Bay area, a gneiss domain north of Chesterfield Inlet in Nunavut. Igneous crystallization ages of 2707 ± 8 Ma, 2699 ± 11 Ma, and 2701 ± 14 Ga were obtained, respectively, from a tonalitic biotite-hornblende gneiss, a foliated tonalite, and a foliated granodiorite. Five inherited zircons from the latter have ages in the range 2960 to 2906 Ma. These three intrusive rocks are coeval with, and therefore not basement to, the Woodburn Lake and Prince Albert groups. A younger age of 2584 ± 12 Ma was obtained from a foliated hornblende-biotite granodiorite, which corresponds to widespread plutonism in the Rae Province. Metamorphic zircon overgrowths from two samples yielded ages of 1865 ± 10Ma and 1863 ± 14 Ma, respectively, which are interpreted in terms of regional metamorphism preceding the 1845 to 1795 Ma crustally derived Hudson granite intrusions. Sm-Nd crystal separation ages (T(DM)) for twelve samples range from 3.08 to 2.53 Ga and indicate the existence Mesoarchean crust in the area. Six of the T(DM) ages are in the 2.83 to 2.72 Ga range, which also characterizes T(DM) ages in much of the western Churchill Province. The majority of the samples feature LREE enrichment, HREE depletion, negative to slightly positive Eu/Eu* anomalies, and Nb depletion. Two samples with 2.56 Ga and 2.53 Ga T(DM) ages have compositions that differ markedly from the main population in having positive Eu/Eu* anomalies and extreme HREE depletion.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".