Is PREMA exclusively associated with LLSVPs?
Bibliographic record
Abstract
Studies of ocean island basalts (OIBs) have identified a “Prevalent Mantle” component (or PREMA) that appears to represent one of the fundamental constituents of Earth’s mantle. Recent documentation of this signature in deep-sourced kimberlitic magmatism has increasingly linked PREMA with thermochemical structures above the core mantle boundary (LLSVPs). Yet, kimberlites provide geographically limited sampling of Earth’s mantle, which makes it difficult to identify the spatial association between LLSVPs and the PREMA component sampled by these magmas. To further investigate the global distribution of the PREMA mantle component, we utilize a much more widespread class of mantle-derived magmatism – global Cenozoic alkali basalts, nephelinites and basanites (‘sodic basalts’ hereafter) – that are derived from both continental and oceanic settings. Statistical treatment of the available ~3500 geochemical and isotopic analyses of Cenozoic sodic basalts worldwide shows that at low degrees of melting these magmas exhibit similar Sr-Nd-Hf isotopic characteristics to PREMA. There is no apparent spatial relationship between the distribution of PREMA-like sodic basalts and LLSVPs, implying that the PREMA component is not exclusively associated with LLSVPs. The PREMA-like signature of low-degree sodic basalts occurs in both OIBs and continental magmas, negating an exclusive link to continental lithosphere. Geochemical modelling and mantle convection simulations indicate that PREMA could have been generated soon after Earth accretion, experiencing only minimal melting or enrichment, and then scattered throughout the mantle, including the upper mantle, rather than being the result of mixing between depleted and enriched mantle components. This work indicates that PREMA probably represent a widespread fusible component that can be mingled with other components at various scales to generate all types of mantle magmatism.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".