The Golden Bar pit is part of the Macraes mine, the largest
gold mine in New Zealand. The
Macraes mine is mainly developed in the late metamorphic Hyde-Macraes Shear
Zone. However, the Golden Bar pit was developed in a mineralised zone about 200
m structurally above the Hyde-Macraes Shear Zone. The host rocks are dominated
by massive quartzofeldspathic schist (5 - 10 m layers) with minor intercalations
(1 - 5 m scale) of micaceous schist. All the host schist has disseminated pyrite
(micron to mm scale) from pervasive late metamorphic hydrothermal
alteration.

In addition, there has been more localised (metre scale)
relatively intense hydrothermal alteration controlled by shears subparallel to
foliation. Gold occurs in three types of mineralised rock: silicified schist,
which dominates, fissile black sheared rock, and cross-cutting quartz veins.
There are three principal structural zones in the deposit:
1. a strongly
sheared micaceous and graphitic zone at the base of the structural sequence;
2. a weakly
deformed schist zone cut by relatively flat-lying ( 20 dipping) quartz veins;
and
3. a stack of
imbricated schist pods and deformed silicified schist confined between two
sub-parallel low-angle (ca. 30) shears.

These structural zones were juxtaposed during thrust
deformation. The lower black shear zone has m-scale folding and over-thrusting
packages, kink folding and foliation stacking with associated striations that
imply west-directed thrusting. Striations and imbrication geometry between the
upper two shears imply oblique thrusting that was directed towards the west.
Post-mineralisation normal faults locally disrupt the mineralised zone. The
Golden Bar pit mineralised zone has some of the structural and mineralogical
characteristics of the main Hyde-Macraes Shear Zone, and may be genetically
related.