Tracking the Geochemical Transition Between the Kea‐Dominated Northwest Hawaiian Ridge and the Bilateral Loa‐Kea Trends of the Hawaiian Islands
Bibliographic record
Abstract
Abstract For ~82 million years, the Hawaiian‐Emperor chain volcanoes have sampled the Pacific mantle via the Hawaiian mantle plume, providing evidence that its composition varies on a range of temporal and spatial scales. Hawaiian volcanoes from 2 to 0 Ma are divided into southwestern (Loa) and northeastern (Kea) geographic and geochemical trends that are interpreted to reflect the bilateral chemical structure of the underlying plume and its corresponding deep mantle sources. Hawaiian volcanoes that formed between 8 and 3 Ma record a geochemical transition between the Kea‐dominated Northwest Hawaiian Ridge (49 to 8 Ma) and the bilateral trends of the younger Hawaiian Islands. High‐precision Pb isotopic analyses conducted on 55 new shield‐stage samples from two of these key volcanoes, Kaua‘i and Wai‘anae, show that Loa‐like Pb isotopic ratios (e.g., elevated 208Pb*/206Pb*) gradually increase with decreasing age among the northern Hawaiian volcanoes and dominate for over 2 million years prior to the onset of the bilateral Loa and Kea geochemical trends. Distinct isotopic groups are observed across Kaua‘i and the distribution of Loa and Kea isotopic compositions is rotated relative to that observed on the younger Hawaiian Islands. Protracted Loa compositions and the atypical Loa‐Kea trend on Kaua‘i are accounted for by (1) the arrival of a voluminous, Loa mantle heterogeneity possibly associated with anchoring of the Hawaiian plume to the Pacific Large Low Shear Velocity Province and (2) a different orientation of the Pacific plate relative to the Loa‐Kea compositional boundary prior to 2 Ma.
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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 | 0.000 | 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".