Volcanogenic processes and petrogenesis of the early Pleistocene andesitic-dacitic Maungatautari composite cone, Central Waikato, New Zealand

Maungatautari is an extinct, andesitic-dacitic composite cone situated 35 km southwest of Hamilton, New Zealand. This study examines the volcanic history and petrologic evolution of Maungatautari using field mapping, petrography of pyroclastic successions and lavas, and whole rock and isotope analyses of selected lavas. Lavas consist of non-vesicular labradorite, pyroxene and hornblende andesites and dacites. A small cone of olivine basalt is located at Kairangi, 7 km to the northwest of the Maungatautari trig. Whole rock geochemical and strontium and neodymium analyses demonstrate that these lavas were derived from at least three distinct mantle-melt sources. Mass-wasting processes continue to shape the mountain post volcanic activity and include catastrophic failure of the north-eastern flank which produced a 0.28 km(3) rock avalanche deposit. This study considers Maungatautari to reflect andesitic-dacitic arc volcanism occurring within the upper North Island c. 2 Ma.