Abstract

It is commonly accepted that large igneous provinces are formed through catastrophic volcanic events occurring over vast areas within a few million years at the initiation of hotspots (mantle plumes). New 40Ar/39Ar ages (111–139 Ma) and geochemical results from the Nicoya Peninsula, Costa Rica, extend the age range of volcanism in the Caribbean large igneous province to 70 m.y. (69–139 Ma). Our results are not consistent with the formation of this vast igneous province through a single plume head at the initiation of a mantle plume such as the Galápagos. Instead we propose that multiple oceanic intraplate igneous structures, such as plateaus and hotspot tracks, were accumulated through the subduction process. The igneous structures could be remnants of the earlier history of the Galápagos hotspot, making it one of the oldest active hotspots on Earth. Alternatively they could have been derived from several spatially distinct mantle-melting events that sampled similar source material, e.g., oceanic lithosphere of similar age.

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