The Origin of Intraplate Volcanism in New Zealand

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Intraplate volcanism has occurred nearly continuously in different parts of Zealandia (New Zealand microcontinent) since it began to break away from Gondwana at ca 110 Ma. Even though Zealandia has moved 6000 km to the northwest with respect to the underlying mantle since it separated from Antarctica, the volcanism does not continue onto the adjacent ocean floor and thus seems to be linked to the microcontinent. The volcanism is widespread but generally of low volume except the large mid to late Miocene composite shield volcanoes forming the Banks and Otago Peninsulas. In addition, it occurred repeatedly in several restricted areas throughout the Late Cretaceous and the Cenozoic. The origin of this volcanism on Zealandia cannot be adequately explained by either of the major models for intraplate continental volcanism: 1) passage of the lithosphere over mantle hotspots (or plumes) or 2) decompression melting related to lithospheric thinning resulting from continental rifting. Combining regional age dating with petrologic and geochemical investigations, we propose to reconstruct the temporal and spatial evolution of the Late Cretaceous to Quaternary volcanism. In collaboration with New Zealand colleagues, we will develop a model explaining intraplate volcanism on Zealandia, which can also be applied to other fast moving plates with large variations in lithospheric thickness. The project promises to provide fundamental new insights into the origin of intraplate volcanism.