Gravitational expression of the dunedin volcano

Abstract

The isostatic gravity anomaly map of the Dunedin Volcanic Complex shows a circular positive anomaly centred near Portobello, the focus of the initial eruptive activity. The cause of this anomaly is identified with the intrusive rocks of the feeding system of the Miocene volcano. A vertical cylindrical model of the feeding system, fitted to the observed anomalies by the method of least squares, suggests that an underlying volume of crust of diameter 13 km and depth 10 km has been invaded and partly replaced by dense intrusives, giving it a positive density contrast of 0·08 Mg/m3. The volume of intrusives deduced from this model, about 600 km3, is at least five times greater than that of the erupted rocks. © 1972 Taylor & Francis Group, LLC.