Neoarchean marine chemical sediments as archives of Hadean silicate differentiation
Bibliographic record
Abstract
Planetary differentiation had a profound influence on the geochemical signature of the Earth's silicate reservoirs.Some of the early created complementary reservoirs dissipated with time (e.g., Bennett et al., 2007) and only remnants can be observed.Here, we apply the short lived isotopic system 146 Sm-142 Nd to an alternative archive -marine chemical sediments-and show that alternating Fe-and Si-rich bands from the 2.7 billion-year-old Temagami banded iron formation (BIF), Canada, display significantly different 142 Nd isotopic compositions.The Fe-rich bands yield a depleted signature (expressed as deviation from the standard in μ notation) with an average μ 142 Nd of þ7.02 ± 0.71, while the Si-rich bands display modern mantle-like signatures (average μ 142 Nd -2.83 ± 2.32) likely being the results of mixing between different sources.These complementary signatures reflect the dominant, locally derived source of Nd in the seawater at the time of deposition.Our results promote that layering in BIFs is a syn-depositional feature, and that BIFs are unique geochemical archives capable of recording silicate reservoirs that formed during the Hadean but were still extant during the Neoarchean.
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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 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".