The
Rise and Shine Shear Zone is a mineralised low angle deformation zone traceable
for at least 7 km through biotite zone schist of the Dunstan Range, central Otago. Rocks from the shear
zone obtained from recent drillholes are unweathered and facilitate paragenetic
studies. There is a progression of mineral deposition from semiductile
foliation-parallel shearing, to subsequent folding, and brittle fracturing.
Sheared rocks are dominated by microshears containing fine grained hydrothermal
muscovite and rutile that has recrystallised from metamorphic muscovite and
titanite respectively. Euhedral pyrite occurs within segregations in the schist
and is locally brecciated by the shears.

Arsenopyrite occurs
within microshears and is intergrown with hyrothermal muscovite. Fractures
within relatively undeformed schist are filled with ankerite, siderite,
chalcopyrite, sphalerite and galena and these veinlets also crosscut the
microshears. Locally the schist is folded and zones of brecciation,
silicification and vein deposition overprint the rock. Vein quartz and albite
predominate and arsenopyrite and gold infill breccia matrix and crosscutting
veinlets. Sulphide deposition began in the later stages of metamorphism with
pyrite deposited in quartz-albite segregations. Subsequent shearing caused
brecciation of some grains and accompanied deposition of arsenopyrite gold and
rare sulphides along foliation-parallel microshears. Minor amounts of
chalcopyrite, sphalerite and galena were then remobilised in ankerite veins that
crosscut the shears. In areas of high strain, arsenopyrite was then deposited as
euhedral grains in veins and breccias. Synmineralisation deformation caused the
brecciation of some grains and gold was deposited infilling fractures in the
arsenopyrite. The paragenetic sequence shows gold mineralisation occurred in two
distinct sets of structures (semiductile and brittle) that formed at different
times in the formation of the shear zone.