Bibliographic record
Abstract
Concentrations of trace elements with bulk distribution coefficients < 1 have been utilized to discriminate between mafic magmas erupted in different tectonic settings. Herein, the NbYZr contents of mafic lavas will be utilized to pinpoint derivation from a deep-mantle source. Magmas derived from the Icelandic plume exhibit ΔNb > 0, where ΔNb = log (Nb/Y) + 1.74 1.92 log (Zr/Y) (Fitton et al. 1997), whereas melts derived from depleted sections of the mantle and the crust show ΔNb < 0. Regardless of the nature of the melting event, it was suggested the ΔNb value of magmas were essentially identical to that of the source material. Theoretical modeling of a garnet lherzolite source suggests very small partial melts may show elevated ΔNb values, yielding a spurious plumelike signature. For mafic rocks from different areas, with hypothesized hot spot derivation, ΔNb is calculated to search for a deep-mantle signature (ΔNb > 0). The signature of the Réunion hot spot, from ~650 Ma, is seen in the Deccan Traps, India, lavas from the Mascarene Plateau, and Réunion Island. The signature of the Kerguélen plume is detected in rocks from Kerguélen Island and the Ninetyeast and Broken Ridges, Indian Ocean, a few lavas from the Rajmahal province, India, but none in the Bunbury Basalt, Australia. Some rocks from continental flood basalt provinces show a hot spot component, in agreement with conclusions based on 3He/4He studies, others show ΔNb < 0, due to considerable subcontinental contamination. For lavas from Heard Island and Grand Comore, Indian Ocean, the technique pinpoints those showing a plume component. In an area of plate convergence in the Pacific Ocean, lavas with very low (<1 ppm) Nb contents, serve as a critical test for this method. Only rocks close to the Samoan hot spot show ΔNb > 0, whereas the others show the Nb depletion typical of arc-related material. In conjunction with trace-element and isotopic discriminants, this appears to be a useful tool in identifying a deep-mantle component in mafic lavas from a variety of plate tectonic settings.
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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 | 0.003 | 0.001 |
| 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) | 0.003 | 0.001 |
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".