Oceanic serpentinites: A potentially critical reservoir for deep nitrogen recycling
Bibliographic record
Abstract
Abstract Serpentinized oceanic peridotites might be an important reservoir delivering volatile elements including nitrogen (N) into the mantle via subduction. To determine N sources and estimate the budget of alteration-added secondary N in the oceanic mantle peridotite reservoir, we examined oceanic serpentinites from four Ocean Drilling Program (ODP) sites in the Pacific and Atlantic Oceans. Our results showed that, despite large variation in serpentinization condition (high temperatures up to >350 °C at Holes 895D, 1271B, and 920D; low temperatures <150 °C at Hole 1274A), serpentinites from all sites displayed ubiquitous and similar magnitude of N enrichment (3.2–18.6 ppm) from sediments/seawater sources (δ15N = –3.3‰ to +4.4‰), and these values were significantly elevated relative to the low N concentration (0.04–2.0 ppm) and δ15N value (−5‰ ± 2‰) of the depleted mantle. Based on these data, the serpentinized oceanic mantle is estimated to contribute 0.4 ± 0.2–14.7 ± 6.9 × 109 mol N annually to global subduction zones. Although this flux is smaller than that of subducting sediments (57 × 109 mol·yr–1), comparison between oceanic serpentinites and meta-serpentinites from subduction zones suggests that N can be effectively retained in serpentinites during prograde metamorphism. This implies that the serpentinized slab mantle could be a critical reservoir to deliver N enriched in 15N to the mantle (at least 70 km depth) and potentially to the deepest portions of the mantle sampled by deep-rooted mantle plumes.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".