Geology of young submarine volcanoes west of Easter Island, Southeast Pacific

Abstract

Submarine volcanoes, probably related to the Easter hotspot, were found between the Easter Microplate and Easter Island near 26°15′S, 111°W. Hydrosweep swath mapping accompanied by deep-towed camera observations and sampling revealed the presence of fresh lava flows confined to two distinct fields, the previously-known Ahu and the newly discovered Umu Volcanic Fields, covering a combined area of more than 4300 km 2. These lava fields form constructional ridges with volcanic cones as well as isolated seamounts. Another large volcanic area, probably also belonging to the Easter hotspot, was found 100 km south of the Ahu/Umu region. Thus the young hotspot region has a diameter of about 200 km and its centre probably lies underneath the Umu Volcanic Field rather than under Ahu Volcanic Field. The fresh volcanics recovered from these areas are olivine and plagioclase phyric enriched and, more rarely, depleted tholeiites. The enriched lavas are comparable to E-MORB from the Easter Microplate spreading axes and volcanic ridges and seamounts west of the microplate.