Shield Through Rejuvenated-Stage Volcanism and the Evolution of Alkalic Lavas on West Maui, Hawaii – Insights on Magma Source and Processes Along the Hawaiian Island Chain
Bibliographic record
Abstract
Hawaiian volcanoes develop through age-progressive growth stages that reflect passage of their volcanic edifice over the Hawaiian Plume. West Maui is the youngest volcano to have experienced a shield, postshield, and rejuvenated-stage of development and is unique in that tholeiitic shield-stage volcanism is abruptly followed by the appearance of felsic lavas i.e. benmoreite and trachyte. This absence of mafic-intermediate alkalic lavas on West Maui forms a “Daly Gap”. ~0.6 Ma after cessation of shield and postshield-stage volcanism, West Maui experienced a brief period of rejuvenation which produce four discrete eruptions of basanite. This study aims to explain the unique temporal changes on West Maui and better constrain spatial heterogeneities in the source of Hawaiian lavas. Rejuvenated lavas on West Maui are enriched in incompatible elements yet have steep 206Pb/204Pb versus 208Pb/204Pb and 143Nd/144Nd versus 176Hf/177Hf well below the mantle array that trends toward Pacific MORB lavas. Our models indicate a depleted upper asthenosphere metasomatized by the Hawaiian Plume as the source of rejuvenated lavas on West Maui. This source is now identified to be long-lived on northern or Kea-trend volcanoes and invokes more recent models of plume-lithosphere interaction. West Maui’s postshield lavas have overlapping radiogenic isotope signatures with shield lavas suggesting a similar plume source. They however have less radiogenic Pb (208Pb*/206Pb*) and relatively high 206Pb/204Pb at a given 87Sr/86Sr indicating a more depleted signature than shield-stage lavas. A transition to a more depleted signature is common among other Hawaiian postshield lavas and indicates that enriched components are consistently exhausted during shield-stage volcanism and/or the shift towards the plume’s periphery allows entrained upper-mantle to be preferentially melted. In the absence of continental crust, felsic oceanic lavas are thought to originate by partial melting of hydrated basalt or as products of extensive fractionation. Major and trace element trends of mafic-intermediate lavas from Kohala’s postshield indicate a similar source to West Maui’s postshield. Mass-balance calculations show that West Maui trachytes are a 14% residual liquid after fractional crystallization from an inferred mafic source similar to alkalic basalts from Kohala. Postshield lavas evolved at depths of >20 km and erupted along established shield-stage rifts.
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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 | 0.001 | 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".