Compositional and textural characteristics of the strombolian and surtseyan K‐Trig basalts, Taupo Volcanic Centre, New Zealand: Implications for eruption dynamics

Abstract

Abstract K‐Trig basalts form a NNE lineament of four monogenetic centres, along the eastern side of the Kaiapo Fault, 4 km west of Taupo, New Zealand. Exposures of the northernmost centres (Punatekahi and K‐Trig) are dominated by strombolian volcanism, whereas the southern centres (Kaiapo and Mine Bay) are products of surtseyan activity. The Kaiapo deposit represents the faulted, eroded remnant of a once larger phreatomagmatic tuff cone. Inner‐wall stratigraphy exposed in the Kaiapo Fault scarp shows the deposit built up during three phases of phreatomagmatic volcanism, each phase comprising a lapilli‐rich lower facies A and a contrasting lapilli‐poor upper facies B. Both are interpreted as the product of multiple “wet” surges, but facies A beds are classic surtseyan products, whereas facies B beds are interpreted as having been deposited during periods of lower magma flux, when decoupled magmatic volatiles streamed through a fine‐grained vent slurry, facilitating weak steam explosions. At Punatekahi, two...