Petrology, geochemistry, and ages of lavas from Northwest Hawaiian Ridge volcanoes
Bibliographic record
Abstract
The Northwest Hawaiian Ridge is a classic example of a large igneous province. The morphology and geology of the ridge is poorly characterized, although it constitutes the longest segment (~47%) of the Hawaiian-Emperor Chain. Here we present a new bathymetric compilation, petrographic and X-ray fluorescence (XRF) data for lavas from 12 volcanoes along the Northwest Hawaiian Ridge, and review literature data for the age and isotopic variation of the ridge. The bathymetric compilation revealed that the Northwest Hawaiian Ridge consists of at least 51 volcanoes. The 45 new XRF analyses show that the Northwest Hawaiian Ridge contains tholeiitic and alkalic lavas with compositions typical of lavas from the Hawaiian Islands. The absolute ages and duration of volcanism of individual Northwest Hawaiian Ridge volcanoes are poorly known, with modern 40Ar/39Ar ages for only 10 volcanoes, mostly near the bend in the chain. We infer the initiation age of the Hawaiian-Emperor Bend to be ca. 49–48 Ma, younger than the age for the onset of island arc volcanism in the western Pacific (52–51 Ma). Thus, the kink in the Hawaiian-Emperor Chain and the onset of arc volcanism were not synchronous. Isotopic data are sparse for the Northwest Hawaiian Ridge, especially for Pb and Hf. Two transitional lavas from just south of the bend have Loa trend type Pb and Sr isotopic ratios. Otherwise, the available chemistry for Northwest Hawaiian Ridge lavas indicates Kea-trend source compositions. The dramatic increase in melt flux along the Hawaiian Ridge (~300%) may be related to changes in melting conditions, source fertility, or plate stresses.
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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 | 0.002 | 0.001 |
| 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) | 0.000 | 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".