A comparison of Nd model ages and U–Pb zircon ages of Grenville granitoids: constraints on the evolution of the Laurentian margin from 1.5 to 1.0 Ga
Why this work is in the frame
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Bibliographic record
Abstract
Terra Nova, 24, 7–15, 2012 Abstract Concordance and discordance between Nd model ages and U–Pb ages is still widely misunderstood in the geological community. In the SW Grenville Province, plutonic orthogneisses often yield T DM ages significantly older than U–Pb crystallization ages, but this can be understood in a model where a series of crustal Nd isotope evolution lines departs at intervals from the depleted mantle (DM) evolution line. Seven samples with concordant U–Pb and Nd model ages have initial ε Nd on the DM line, attributed to melting of juvenile crust generated in an Elzevirian back‐arc rift zone. In contrast, plutons with discordant U–Pb and Nd model ages lie near crustal evolution lines defined by suites of basement gneisses on the flanks of the rift zone. This study shows that Nd data from large suites of geographically constrained, undated grey gneiss provide a crustal evolution framework for orogen‐scale interpretation of more scattered but precisely dated plutons.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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 it