Posterosional volcanism in the Cretaceous part of the Hawaiian Hotspot Trail

Abstract

Multibeam bathymetry and seismic reflection profiling shows the Cretaceous products of the Hawaiian hotspot to be a ridge of coalesced guyots that prolong the N‐NW trend of the more isolated Paleocene Emperor Seamounts, a 10,000 km 2 plateau (Detroit Plateau), where the trail changes strike to NW, and the Obruchev Rise hotspot ridge, which extends to the Kamchatka Trench. The northernmost guyots were submerged and tilted southeast by the load of new shield volcanoes added to the end of the chain, then secondary volcanism built small cones on their summit platforms and in a gap between two guyots. Dredged rock samples and the distribution of the cones indicates that on one guyot these submarine eruptions were in the alkalic postshield stage of Hawaiian volcanism, and at another were probably in the alkalic rejuvenated stage. Seamount‐building eruptions at Detroit Plateau produced lavas (nepheline melilitites) that belong geochemically to the alkalic rejuvenated stage, and are very similar to Pleistocene lavas in the Hawaiian Islands. However, these eruptions postdated passage off the hotspot plume by a much longer time than the 0.5–2.5 m.y. observed in the Hawaiian Islands, and were probably initiated by different tectonic processes.