The Depleted Component in the Galapagos Lavas and the Role of the Oceanic Lithosphere

The diverse geochemical characteristics of lavas from the Galapagos Islands reflect, in part, the mantle heterogeneity beneath the archipelago. Although, the origin of the enriched end member mantle components has been discussed extensively (mainly as the product of sediments, oceanic crust and lithospheric mantle recycled into the mantle at subduction zones), the role of the depleted component in the Galapagos lavas has received less attention. Furthermore, the few studies that considered such a component have proposed two contrasting hypothesis about the origin of the depleted component in the Galapagos lavas. Blichert-Toft and White (2001) argued that the depleted component is the usual surrounding depleted MORB mantle source, while Hoernle et al. (2000) considered such component an intrinsic part of the plume. We compile published trace elements and isotopic composition of lavas with MgO > 5 wt% from the Galapagos archipelago using GEOROCK database, and measured trace elements and isotopes of few primitive lavas from across the archipelago selected to be younger than 30,000 years to avoid the problem of temporal variation. The data indicate that the source of the depleted component is not an intrinsic part of the plume, but a component that resides in the oceanic lithosphere, which was entrained into the plume's melts as they migrate toward the Earth surface.