Abstract

The classical model for the generation of hotspot tracks maintainsthat stationary and deep-seated mantle plumes impinge on overridingtectonic plates, thereby generating age-progressive trails ofvolcanic islands and seamounts. Samoa has played a key rolein discrediting this model and the very existence of mantleplumes, because early geochronological work failed to demonstratea linear age progression along this chain of islands. Specificallyon Savai'i Island, the bulk of the subaerial volcanics is youngerthan 0.39 Ma, much younger than the 5.1 Ma age predicted fromthe classical hotspot model and a constant 7.1 cm/yr Pacificplate motion. This discrepancy led to alternative magma-producingmechanisms that involve the cracking of the lithosphere beneaththe Samoan islands, as a result of the extensional regime generatedby the nearby Tonga Trench. Here we report ⁴⁰Ar/³⁹Ar ages fromthe submarine flanks of Savai'i Island showing that its volcanicconstruction began as early as 5.0 Ma and in a true intraplatesetting. This reinstates Samoa as a primary hotspot trail associatedwith a deep mantle plume and a linear age progression.