Role of mantle flow at the North Fiji Basin: Insights from anomalous topography
Bibliographic record
Abstract
The North Fiji Basin is a complex back‐arc system situated between the opposite‐verging Tonga and New Hebrides subduction zones. On the basis of two independent calculations, we find that the back‐arc region is anomalously high with topography residuals reaching up to 2000 m above what should be isostatically supported. Our study aims to test whether a hot buoyant upwelling is required beneath the North Fiji Basin to support the observed high elevation. The mantle thermal structure beneath the North Fiji Basin is inferred from the global tomographic model S20RTS, where seismic velocity anomalies are converted to density/temperature anomalies. This thermal structure is input into a three‐dimensional mantle convection code, CitcomS, and the flow‐induced surface topography is calculated and compared with the observed anomalous topography. In a series of experiments, we eliminate various portions of the mantle structure to consider what type of mantle flow can support the anomalous topography. The experiments suggest that the observed topography in the North Fiji Basin is consistent with the support of hot buoyant upper mantle upwelling, and specifically rising material in the depth range from 70 to 120 km is the most critical component. A relatively thin/weak lithosphere is required to produce the high‐amplitude and short‐wavelength topography residuals, and the presence of discrete breaks in the plate produces further localization of flow‐induced topography.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".