Petrogenesis of high-K arc magmas: Evidence from Egmont Volcano, North Island, New Zealand

Abstract

Egmont Volcano (Mt Taranaki) is located 140 km west of the Taupo Volcanic Zone (TVZ), the principal locus of volcanic activity in the North Island of New Zealand, and is one of four closely associated Quaternary andesitic volcanoes in Taranaki province. Taranaki eruptives are enriched in K and other large ion lithophile elements compared with their counterparts at Ruapehu in the southern TVZ with the youngest Egmont andesites being the most K rich. Egmont andesites are invariably fractionated but isotopic information indicates that, unlike those at Ruapehu, they have not extensively assimilated enriched crust. Ti/Zr, Ba/La, Ce/Pb, and K/Rb ratios indicate that a more depleted mantle wedge an..