Geological Origin of the Volcanic Islands of the Caroline Group in the Federated States of Micronesia, Western Pacific

We present a geological review of the volcanic islands of the Caroline Islands group (Yap, Chuuk, Pohnpei and Kosrae) of the Federated States of Micronesia, to understand the origin and mechanism of formation of these volcanic islands. Previous geochronological data from the three volcanic islands (Chuuk: 14.8 to 4.3 Ma; Pohnpei: 8.7 to 0.92; and Kosrae: 2 to 1 Ma), indicate a progressive increase in age towards west, based on which a hot-spot origin was assigned. However, overlap in age of the volcanic islands and the absence of a hot spot east of Kosrae suggest involvement of other tectonic activity for their formation besides the simple hot-spot model. By observing geological features in the field (e.g., occurrence of structurally younger dikes which cross-cut the older volcanic sequences, presence of extensive dikes with columnar joints; indicative of extensional environment) and literature survey, we consider that the Caroline volcanic islands were not only remnants of a hot spot trace; as generally agreed by many authors, but were also produced in a fracture-induced subduction-related tectonic environment