Carbonatite and Silicate Melt Metasomatism of the Mantle Surrounding the Hawaiian Plume: Evidence from Volatiles, Trace Elements, and Radiogenic Isotopes in Rejuvenated‐stage Lavas from Niihau, Hawaii

Authors

Jacqueline Dixon, University of MiamiFollow
David A. Clague, Monterey Bay Aquarium Research Institute
Brian Cousens, Carleton University
Maria Luisa Monsalve, University of Miami
Jessika Uhl, Carleton University

Document Type

Article

Publication Date

9-2008

Keywords

Hawaii, alkalic, trace elements, volatiles, metasomatism, rejuvenated‐stage lava

Digital Object Identifier (DOI)

https://doi.org/10.1029/2008GC002076

Abstract

We present new volatile, trace element, and radiogenic isotopic compositions for rejuvenated‐stage lavas erupted on Niihau and its submarine northwest flank. Niihau rejuvenated‐stage Kiekie Basalt lavas are mildly alkalic and are isotopically similar to, though shifted to higher ⁸⁷Sr/⁸⁶Sr and lower ²⁰⁶Pb/²⁰⁴Pb than, rejuvenated‐stage lavas erupted on other islands and marginal seafloor settings. Kiekie lavas display trace element heterogeneity greater than that of other rejuvenated‐stage lavas, with enrichments in Ba, Sr, and light‐rare earth elements resulting in high and highly variable Ba/Th and Sr/Ce. The high Ba/Th lavas are among the least silica‐undersaturated of the rejuvenated‐stage suite, implying that the greatest enrichments are associated with the largest extents of melting. Kiekie lavas also have high and variable H₂O/Ce and Cl/La, up to 620 and 39, respectively. We model the trace element concentrations of most rejuvenated‐stage lavas by small degrees (∼1% to 9%) of melting of depleted peridotite recently metasomatized by a few percent of an enriched incipient melt (0.5% melting) of the Hawaiian plume. Kiekie lavas are best explained by 4% to 13% partial melting of a peridotite source metasomatized by up to 0.2% carbonatite, similar in composition to oceanic carbonatites from the Canary and Cape Verde Islands, with lower proportion of incipient melt than that for other rejuvenated‐stage lavas. Primary H₂O and Cl of the carbonatite component must be high, but variability in the volatile data may be caused by heterogeneity in the carbonatite composition and/or interaction with seawater. Our model is consistent with predictions based on carbonated eclogite and peridotite melting experiments in which (1) carbonated eclogite and peridotite within the Hawaiian plume are the first to melt during plume ascent; (2) carbonatite melt metasomatizes plume and surrounding depleted peridotite; (3) as the plume rises, silica‐undersaturated silicate melts are also produced and contribute to the metasomatic signature. The metasomatic component is best preserved at the margins of the plume, where low extents of melting of the metasomatized depleted mantle surrounding the plume are sampled during flexural uplift. Formation of carbonatite melts may provide a mechanism to transfer plume He to the margins of the plume.

Rights Information

Terms of use for work posted in Scholar Commons.

Was this content written or created while at USF?

No

Citation / Publisher Attribution

Geochemistry, Geophysics, Geosystems, v. 9, issue 9, art. Q09005

Copyright 2008 by the American Geophysical Union.

Scholar Commons Citation

Dixon, Jacqueline; Clague, David A.; Cousens, Brian; Luisa Monsalve, Maria; and Uhl, Jessika, "Carbonatite and Silicate Melt Metasomatism of the Mantle Surrounding the Hawaiian Plume: Evidence from Volatiles, Trace Elements, and Radiogenic Isotopes in Rejuvenated‐stage Lavas from Niihau, Hawaii" (2008). Marine Science Faculty Publications. 1308.
https://digitalcommons.usf.edu/msc_facpub/1308