Heading down early on? Start of subduction on Earth
Bibliographic record
Abstract
How the Earth’s earliest crust was formed and when present-day plate tectonics (i.e., subduction) and life commenced remain fundamental questions in Earth sciences. Whereas the bulk composition of the crust is similar to that of rocks generated in subduction settings, it does not necessarily follow that melting and crust formation require subduction. Many workers suggest that subduction may have only commenced toward the end of the Archean or later. Here we observe that both the stratigraphy and geochemistry of rocks found in Quebec, Canada, that have been variously argued to be 4.4 or 3.8 Ga in age, closely match those from the modern-day Izu-Bonin-Mariana forearc. We suggest that this geochemical stratigraphy might provide a more robust test of ancient tectonic setting than individual chemical or isotopic signatures in rocks or detrital minerals. If correct, the match suggests that at least some form of subduction may have been operating as early as the Hadean or Eoarchean. This could have provided an ideal location for the development of first life.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.013 | 0.002 |
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".