A fresh look at the Sm-Nd record of Earth’s oldest rocks: the Acasta Gneiss Complex (Northwest Canada)
Why this work is in the frame
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Bibliographic record
Abstract
The earliest differentiation of the silicate Earth remains poorly constrained due to the scarcity and imperfect preservation of Earth's oldest rocks. These limitations can be circumvented, however, using the short-lived 146 Sm-142 Nd system, which provides selective chronological information on Hadean crustmantle differentiation processes [1] . The oldest rock record on Earth is represented by a chemically diverse suite from the 3.6-4.0 Ga Acasta Gneiss Complex (AGC) in northwest Canada [2,3] . Previous 146 Sm-142 Nd studies of the AGC revealed the presence of negative 142 Nd anomalies, inherited from a so-far elusive Hadean crustal component [4,5,6] . However, the majority of AGC samples define a 147 Sm-143 Nd regression age of 3.37 0.14 Ga [7] , suggesting late disturbance of their Sm-Nd systematics. This issue limits the potential of combined 146,147 143 Nd investigations to reveal the timing of Hadean crust-mantle differentiation.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.048 | 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