The Age and Composition of the Voyager Seamounts: Evidence for a Long-Lived Marquesas Mantle Source

We present new observations on the dynamics and locations of deep mantle reservoirs derived from the ages and compositions of Voyager Seamount Chain lava flows. The previously unexplored Voyager Seamount Chain trends NW–SE between the Mid-Pacific Mountains and the Northwestern Hawaiian Ridge. Volcanic samples were recovered from the chain during the Ocean Exploration Trust expedition NA134. The lava flows are alkalic to highly alkalic in composition. Ages ranged from 81 to 86 Ma (n = 8), with the oldest ages in the NW and an age-progression toward the SE. The Voyager age-progression continues southward through the Northern Line Islands region until at least 69 Ma. Mantle flowlines using absolute plate motion models indicate that the Voyagers were emplaced near the modern Marquesas Hotspot location approximately 86–69 Ma. The Sr-Nd-Pb-Hf isotope systematics show the influence of an EMII component and overlap the compositions of Pliocene volcanism from the Marquesas Islands, consistent with the plate motion age model. These data imply a long-lived plume as the source of the Voyager seamounts and the Marquesas. However, the lack of a clear and continuous seamount chain between the 86–69 Ma Voyager Seamount Chain and the 6–0 Ma Marquesas Islands implies that the mantle plume displays variable buoyancy flux over time. The surface expression of this mantle reservoir experienced a potential hiatus of up to ∼60 m.y. These new data indicate that the mantle beneath the Marquesas Islands region has been discontinuously producing age-progressive, EMII-like hotspot volcanism since at least the Late Cretaceous.