Factors Influencing Initial State Geothermal Exploration of Small Volcanic Pacific Islands. an Example from Efate Island, Vanuatu

Abstract

A resistivity survey of Efate Island, Vanuatu, made during 1985-86 has located a large low resistivity anomaly in the northern part of the island. This is interperted as representing extensive hydrothermal alteration caused by a geothermal system which feeds currently active neutral chloride hot springs on the northern coast. Geochemical reconnaisance has revealed no acid waters or chloride springs at elevations significantly above seal level. However, evidence of acid alteration was observed in the western part of the resistivity anomaly where low resistivities were found at highest elevation. The source of an active geothermal system probably exists in this north western part of Efate. Problems associated with geophysical reconnaisance on tropical volcanic islands are discussed.