Alkaline magma formation at plate boundaries: insight in the Alexandra Volcanic chain, North Island, NZ

Approximately 2 Myr ago intraplate and subduction magmatism occurred superimposed in space and time with the alkaline intraplate Okete Volcanic Field (OVF) erupting concurrently to the calc-alkaline subduction related Alexandra Volcanics. The OVF represents the transition and onset of intraplate volcanic activity in the region that subsequently migrated northward to the Ngatutura VF (NVF) and South Auckland VF (SAVF) with the Auckland VF (AVF) being the currently active manifestation.

This magmatic sequence and superimposition challenges the plume paradigm as alkaline magmas emitted in the OVF do not show any slab contamination. We want to investigate the relationship of arc calc-alkaline and intraplate alkaline magmas and look at shallow processes occurring in the lithospheric mantle.