Volcanic evolution of Easter Island, SE Pacific: implications for the development of plume-related shield volcanoes

Easter Island (Rapa Nui, Chile) is an intra-oceanic volcanic island on the Easter hot spot, ~350 km E of the Eastern Pacific Rise. We match new field data with previously published age and petro-chemical data to reconstruct the general evolution of the Island. This consists of three main volcanoes (Poike, Rano Kau and the larger Terevaka), which experienced an overall similar and nearly coeval evolution, characterized by two periods: a) build-up of a basaltic shield, culminating in the development of a summit caldera and the emission of more evolved highly porphyritic lavas (ca. 0.78-0.3 Ma); b) rifting along the shield flanks, by means of fissure eruptions (0.24-0.11 Ma). The trend of most eruptive fissures, NNE-SSW to NE–SW, appears to be controlled by the ~NE-SW elongated emerged and submerged morphology of the island. However, while the fissure-forming period at Rano Kau and Poike appears to be associated with reduced magma supply to the reservoir, at Terevaka it is characterized by the arrival of new basic magma, rejuvenating the system. The comparison to other intra-oceanic volcanic islands suggests that, because of its tectono-magmatic features (low eruptive rate, scattered rift zones, scarce lateral collapses), Easter Island represents an end-member type of hot spot volcano, as opposite to Hawaii.