East Molokai and other Kea‐trend volcanoes: Magmatic processes and sources as they migrate away from the Hawaiian hot spot
Bibliographic record
Abstract
There are geochemical differences between shield lavas from the two parallel trends, Kea and Loa, defined by young Hawaiian volcanoes. The shield of East Molokai volcano, at greater than 1.5 Ma, is the oldest volcano on the Kea trend. Sequences of older tholeiitic to younger alkalic basalt that erupted as this volcano evolved from the shield to postshield stage of volcanism are well exposed. Much younger, ∼0.34–0.57 Ma, alkalic basalt and basanite erupted during rejuvenated stage volcanism. Like rejuvenated stage lavas erupted at other Hawaiian volcanoes, rejuvenated stage East Molokai lavas have relatively low 87Sr/86Sr and high 143Nd/144Nd. Such ratios reflect a source component with a long‐term depletion in abundance of incompatible elements. On the basis of positive correlations of 87Sr/86Sr versus 206Pb/204Pb and negative correlations of these isotopic ratios with Nb/Zr, a smaller proportion of this depleted component also contributed to the late shield/postshield lavas erupted at East Molokai and the other Kea‐trend volcanoes, Haleakala and Mauna Kea. At each of these Kea‐trend volcanoes, as the volcano moved away from the hot spot, the extent of melting and magma supply from the mantle decreased, the depth of melt segregation increased, and there was an increasing role for a component with long‐term relative depletion in incompatible elements. This depleted component has Kea‐trend Pb isotopic characteristics and relatively low 208Pb/204Pb at a given 206Pb/204Pb, and it is probably not related to oceanic lithosphere or the source of mid‐ocean ridge basalt. The overlap in Sr, Nd, and Pb isotope ratios of recent Kilauea shield lavas and 550 ka Mauna Kea shield lavas has been used to argue that Kea‐trend shield volcanism samples a vertically continuous, geochemically distinct stripe which persisted in the hot spot source for 550 kyr (Eisele et al., 2003; Abouchami et al., 2005). As Kea‐trend volcanoes migrate away from the hot spot and evolve from the shield to postshield stage, there are systematic changes in Sr, Nd, and Pb isotope ratios. However, the overlap of Sr, Nd, and Pb isotope ratios in late shield/postshield lavas from Mauna Kea (<350 ka) and East Molokai (∼1.5 Ma) show that the periphery of the hot spot sampled by Kea‐trend postshield lavas also had long‐term geochemical homogeneity.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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".