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. The zone is commonly
believed to be similar to the actively mined Macraes deposit. The Rise and Shine
Shear Zone occurs in the immediate footwall of the Thomsons Gorge Fault, a
regional scale Cretaceous normal fault that juxtaposes chlorite zone schist
against biotite zone schist. Most mineralised rocks are deformed and record a
progression from early stages of semiductile deformation to more brittle
cataclasis. Folds in mineralised rocks trend northwards. The mineralised schist
is hydrothermally altered with variable silicification, sericitisation,
chloritisation, replacement of
titanite by rutile and
carbonate alteration. Gold is associated with pyrite and arsenopyrite and occurs
in both ductile and brittle microstructures. Sheared and mineralised schist is
cut by north-striking fault zones which host mineralised quartz veins. Veins in
the shear zone contain hydrothermal albite. Trace element analyses show
enrichment in As, U, Th and rare earth elements. Many of the above features are
similar to Macraes deposit, but there are important differences. In particular,
the Macraes deposit is hosted in lower grade rocks and truncated beneath by a
normal fault, Macraes has no U or Th enrichment, Macraes veins have no albite
and folds at Macraes trend NW-W. Rise and Shine mineralised rocks have no Cr
enrichment and no hydrothermal graphite.