New H2O, CO2 and S concentration data for basaltic glasses from Loihi seamount, Hawaii, allow us to model degassing, assimilation, and the distribution of major volatiles within and around the Hawaiian plume. Degassing and assimilation have affected CO2 and Cl but not H2O concentrations in most Loihi glasses. Water concentrations relative to similarly incompatible elements in Hawaiian submarine magmas are depleted (Loihi), equivalent (Kilauea, North Arch, Kauai–Oahu), or enriched (South Arch). H2O/Ce ratios are uncorrelated with major element composition or extent or depth of melting, but are related to position relative to the Hawaiian plume and mantle source region composition, consistent with a zoned plume model. In front of the plume core, overlying mantle is metasomatized by hydrous partial melts derived from the Hawaiian plume. Downstream from the plume core, lavas tap a depleted source region with H2O/Ce similar to enriched Pacific mid-ocean ridge basalt. Within the plume core, mantle components, thought to represent subducted oceanic lithosphere, have water enrichments equivalent to (KEA) or less than (KOO) that of Ce. Lower H2O/Ce in the KOO component may reflect efficient dehydration of the subducting oceanic crust and sediments during recycling into the deep mantle.
KEY WORDS: basalt; Hawaii; mantle; plumes; volatiles
JACQUELINE EABY DIXON1,* and DAVID A. CLAGUE2
1ROSENSTIEL SCHOOL OF MARINE AND ATMOSPHERIC SCIENCE, UNIVERSITY OF MIAMI, 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149, USA
2MONTEREY BAY AQUARIUM RESEARCH INSTITUTE, PO BOX 628, MOSS LANDING, CA 95039-0628, USA