Atypical hotspot chains: evidence for a secondary melting zone below the Marquesas (French Polynesia)

The atypical age/distance to the hotspot relationships observed for the Marquesas linear chain, which present a considerable scatter, are best explained considering (1) a Pacific plate motion of 10.5 cm yr(-1) in the N115 degrees E direction and (2) rejuvenation of volcanism in Ua Huka island. New K-Ar ages show that the main hotspot activity in Ua Huka emplaced successively shield olivine tholeiites and post-shield alkali basalts between 3.11 +/- 0.04 and 2.43 +/- 0.04 Ma. Then, after a quiescence period of 1.28 +/- 0.06 Myr, two small basanitic volcanoes were emplaced between 1.15 +/- 0.02 and 0.763 +/- 0.013 Ma. With respect to the main hotspot volcanics, their lavas originated from weaker partial melting rates of a deeper source. Field, petrologic and geochemical arguments are consistent with the existence of a secondary melting zone located c. 140 km downstream the Marquesas hotspot, which produced the rejuvenated volcanics.