Tungsten isotopes in Baffin Island lavas: Evidence of Iceland plume evolution
Bibliographic record
Abstract
Tungsten and helium isotope ratios in lavas derived from deeply rooted mantle plumes are tracers of lower mantle compositional heterogeneity or core-mantle exchange. We measured the tungsten isotopic compositions of lavas with exceptionally high-3 He/ 4 He ratios that erupted above the head of the Iceland plume on Baffin Island. These lavas have 182 W/ 184 W ratios that are indistinguishable from the convecting upper mantle, unlike younger lavas in Iceland that have lower 182 W/ 184 W ratios. This implies that only the Iceland plume tail was infused with low-182 W/ 184 W material, likely from the core. If high-3 He/ 4 He helium also comes from the core, then diffusion across the core-mantle boundary may stratify plume-source mantle domains, with elevated 3 He/ 4 He travelling farther into the lower mantle than 182 W/ 184 W anomalies. Over Earth history, tungsten diffusion from the core can explain the decline of 182 W/ 184 W in the convecting mantle. We speculate that the uneven pace of this decline corresponds with evolving lower mantle dynamics.
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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".