Global-scale emergence of continental crust during the Mesoarchean–early Neoarchean
Bibliographic record
Abstract
Abstract The timing of the emergence of subaerial landmasses is equivocally constrained as post-Archean and continues to be a much-debated issue. In this study, we document exceptionally 18O-depleted (δ18O < 4.7‰) Mesoarchean to early Neoarchean magmatism in India that shows a similarity with the coeval low-δ18O magmas reported from Australia, South America, and northern China. Such global-scale low-δ18O magmatism would require high-temperature meteoric water–rock interaction in the uppermost crust synchronous with magma generation, necessitating the emergence of a substantial volume of the continental crust. The timing of this low-δ18O magmatism coincides with the development of extensive, subaerial large igneous provinces, a downward shift in δ18O and Δ17O values in pelitic rocks, the rise of normalized 87Sr/86Sr in seawater, and an intermittent upsurge in the proportion of atmospheric oxygen. We propose that the emergence of substantial volumes of continental crust initiated at ca. 3.2 Ga and peaked at 2.8–2.6 Ga, facilitating the generation of globally distributed low-δ18O magmas, and this event can be linked to the first appearance of atmospheric oxygen.
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How this classification was reachedexpand
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) | 0.028 | 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 teacher head, 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".