An Isotopically Depleted Component Intrinsic to the Hawaiian Mantle Plume
Abstract
Isotopically depleted components have long been recognized in mantle plumes. The Hawaiian mantle plume samples an isotopically depleted component during secondary rejuvenated volcanism, which occurs 0.5-2 million years after the end of shield stage volcanism, and arch volcanism, which occurs about 200 km off-axis of the plume center. We report trace element and radiogenic isotope ratios for a series of shield stage tholeiitic basalts from Mauna Kea, called the high-CaO basalts and they have the same radiogenic isotopic composition as both rejuvenated and arch volcanism. Trace element modeling shows that the high-CaO basalts can be reproduced by higher degree partial melting of the parental composition of secondary volcanism. With overlapping radiogenic isotope ratios and a shared parental source melted to a higher degree, we conclude the Mauna Kea shield stage high-CaO basalts sampled the depleted component that is intrinsic to the Hawaiian plume. In our interpretation of the plum pudding model, isotopically enriched components exist as the plums that are embedded in an isotopically depleted matrix. Enriched components have a lower solidus and melt to a high degree to produce tholeiitic basalts during shield stage volcanism. With the lower solidus enriched components melted during the shield stage, secondary volcanism samples a mostly depleted refractory matrix with a higher solidus that melts to lower degrees due to flexural arch decompression melting. The refractory component is normally not sampled during the shield stage due to the presence of the enriched plums. In the case of the high-CaO basalts, no enriched component was present in their mantle source, allowing the refractory matrix to melt to a higher degree due to higher temperature at the center of the plume, producing the high-CaO basalts.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V52A..08D
- Keywords:
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- 1009 Geochemical modeling;
- GEOCHEMISTRY;
- 1025 Composition of the mantle;
- GEOCHEMISTRY