Seismic recognition of igneous rocks of the Deepwater Taranaki Basin, New Zealand, and their distribution

Abstract

ABSTRACT Numerous igneous bodies within the Deepwater Taranaki Basin are recognised mainly from seismic data and range from Early Cretaceous to Pliocene in age. They were all emplaced within an intra‐plate setting but are scattered apparently at random in time and space. This paper describes the occurrences of igneous rocks within the basin as interpreted from seismic data, and discusses their possible origin. There are no indications of hotspot tracks within the Zealandia micro‐continent so an alternative origin is sought. Previous authors see the main cause of volcanism as decompression melting due to localised lithospheric detachment and the movement of the Zealandia plate across the mantle as incidental. It is suggested that the movement of the Zealandia lithosphere, in the order of 4000 km to the north‐northwest since the Cretaceous, may have caused drag across the asthenosphere, which in turn created transient small‐scale convection cells that assisted the process of decompression melting as a modification to the accepted theory.