The Golden Cross low sulfidation epithermal deposit occurs
in pervasively altered andesite of the Waipupu Formation and in the Waiharakeke
Dacite. The unaltered, post-mineral Whakamoehau Andesite overlies these units.
The Empire zone of the Golden Cross deposit contains a stockwork which is
currently mined by open pit methods, and a series of veins that are mined
underground. Alteration envelops both the underground and open pit
mineralisation. The core of the alteration zone contains silicification, as
quartz veins, and adularia. Shallow portions of the system contain
illite-smectite and a thermally unstable chlorite, tentatively identified as
corrensite, which pass downward into illite and chlorite, respectively.
Replacement calcite occurs widely throughout the altered zone; pyrite is nearly
ubiquitous. This alteration assemblage indicates formation from near-neutral
alkali chloride waters. A late, post-mineralisation alteration assemblage of
calcite, smectite, illitesmectite, kaolinite and siderite presumably formed from
weakly acidic, steam-heated CO2-rich waters.

We have identified eight stages
of vein formation: (1) sulfide veins, (2) black veins, (3) massive veins, (4)
banded veins, (5) thin white veins, (6) crumbly veins, (7) massive/platy calcite
veins, and (8) flattened rhomb calcite veins. Gold mineralisation occurred
relatively early in the lifetime of the system, dominantly during 2 through 4.
The late calcite veins (7 and 8) and early sulfide veins (1) are
barren.