Three cross sections, 200 m apart, display the distribution of indicator hydrothermal minerals across the Empire zone of
the Golden Cross epithermal Au-Ag deposit, Waihi, New Zealand. These minerals are used to interpret the temperature
and composition of hydrothermal fluids. The distribution of interstratified illite-montmorillonite and illite indicate that
temperatures ranged from 140 to >220C, with temperatures above 220C predominating. The mineral assemblage of
quartz-adularia-chlorite-illite-calcite-pyrite envelops the Empire vein system and stockwork, and reflects formation from
an alkali chloride water, whereas the mineral assemblage of replacement calcite-interstratified illite - montmorillonite- kaolinite forms a carapace and reflects formation from a C02-rich steam-heated water. Alkali chloride waters appear
responsible for the epithermal Au-Ag mineralisation.