Geology of the Pico Alto Geothermal Prospect, Terceira Island, Azores

Abstract

A geothermal prospect has been located within the large (25 Quaternary caldera of Guilherme Moniz volcano on the island of Terceira. Alto Volcanic Centre occupies the northern part of the caldera, where concentrated post-coll apse i c i c volcanism demonstrates the 1ikely presence of a magmatic heat source at shallow depth in the crust. Surface hydrothermal activity is confined to a small area (Furnas do Enxofre) on the west bounding fault to Moniz caldera. The area is characterised by hot ground (6500 and weak fumarolic activity. Temperatures of at 150 m depth have been encountered by thermal gradient holes. fossil siliceous sinters occur 5 km north of the area. activity is evident at the surface, a deep geothermal system is postulated to exist beneath Alto Volcanic Centre in the northern part of Guil herme Moni z dera.