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

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) 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. •We mapped 185 buried volcanoes up to 20 km in diameter offshore Canterbury Basin.•We identified monogenetic, polygenetic and large polygenetic volcanic complexes.•Eruption rates varied from 1 to 127 km3/Myr throughout time.•These variations in volcanic activity over time reflect plate tectonic processes in the region.