Formation of hydrothermal sulphide deposits on the Niua volcano, Tofuaarc

The Niua South hydrothermal vent field is an intraoceanic arc volcano-hosted hydrothermal system at the northern terminus of the Tofua-Kermadec arc. The vent field is hosted within a 500-m wide volcanic crater on the eastern flank of the southern summit of Niua volcano and contains several hydrothermal mounds that host clusters of active, high-temperature (up to 325°C) chimneys and abundant inactive spires. This thesis presents results from the first detailed exploration and sampling of this vent field, including descriptions of the mineralogy and geochemistry of the hydrothermal deposits. Two distinct mineralogical suites were identified from 33 sulphide-sulphate chimney and talus samples: a high-temperature (≥300°C), Cu-rich suite and a lower-temperature (