Volcanic geology of the Karitane area, and its relationship to Dunedin Volcano

What is it about?

This paper discusses the volcanic relationship between Dunedin Volcano and eruptives in the Karitane area, Otago, New Zealand. Miocene age eruptions produced a wide range of alkalic lavas at both sites. Karitane lavas are unique in that they contain mafic 'blebs' of chilled magma, distinct from their host rock, that resulted from the mingling of two magmas at depth. We use an integrated dataset of field observations, petrography and geochemistry to illustrate that the Karitane magmas were derived from Dunedin magma reservoirs, which extend c.20 km beyond the topographic boundary of the volcano, and are more dispersed than previously recognised.

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Why is it important?

Our work describes mafic inclusions within evolved volcanic rocks (benmoreite) that were previously undocumented in eastern Otago. We provide a conceptual model for understanding the distribution of magma bodies beneath Dunedin Volcano, using the Karitane Suite and its inclusions as direct evidence for mingling of evolved magma reservoirs with rapidly ascending basanite dikes. This model broadly explains the distribution of evolved vs primitive volcanics in the Dunedin Volcanic Group.