Mantle Plume Helium in Submarine Basalts from the Gal pagos Platform

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Abstract

Helium-3/helium-4 ratios in submarine basalt glasses from the Gal pagos Archipelago range up to 23 times the atmospheric ratio in the west and southwest. These results indicate the presence of a relatively undegassed mantle plume at the Gal pagos hot spot and place Gal pagos alongside Hawaii, lceland, and Samoa as the only localities known to have such high helium-3/helium-4 ratios. Lower ratios across the rest of the Gal pagos Archipelago reflect systematic variations in the degree of dilution of the plume by entrainment of depleted material from the asthenosphere. These spatial variations reveal the dynamics of the underlying mantle plume and its interaction with the nearby Gal pagos Spreading Center.

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