Relationships between volcanism and plate tectonics: A case-study from the Canterbury Basin, New Zealand

Abstract

Buried volcanoes and igneous intrusions of Cretaceous to Pleistocene age are widespread in the Canterbury Basin, New Zealand. Interpretation of 2D and 3D seismic reflection lines correlated to petroleum exploration wells reveal over 185 buried volcanic systems formed in association with tectonic activity since the separation of Zealandia from Eastern Gondwana. We characterise these volcanoes according to their size, age and spatial distribution. Small-volume scattered monogenetic (<10 km3) and polygenetic vents (>10 km3) erupted during ~105–85, ~65–13 and ~ 5–1 Ma time intervals. In contrast, large polygenetic volcanic complexes (>100 km3 of erupted magma) formed from ~85–66 and ~ 13–5 Ma. Magmatic intrusions are widespread in the basin, where they are commonly emplaced into Cretaceous to Eocene sedimentary strata. The eruption rates within the offshore Canterbury Basin varied through time, reaching maximum values of ~58–127 km3/Myr immediately after the onset of Late Cretaceous Gondwana break-up (~85–66 Ma) and in the Mid-Late Miocene (~15–5 Ma). Late Cretaceous volcanism may reflect the far-field (>600 km) manifestation of volcanism along the Antarctica-Zealandia spreading centre. Vents and intrusions are located near Cretaceous rift faults which, in some cases act as conduits for magma to ascend to the surface.