The Southern Alps is an active
oblique collisional zone which has a characteristic wedge-shaped geometry above
a low-angle ductile shear zone. The Main Divide region is a relatively low
strain zone above this ductile shear zone, and is _deforming principally along
steeply dipping strike-slip faults. Extensional fractures are common at a high
angle to the regional structural trend. These steeply dipping structures act as
conduits for gold-bearing fluids from depth, and small mesothermal gold deposits
have formed at several structural levels including the near-surface region. Gold
has also been deposited in a meteoricmetamorphic fluid mixing zone near a
conductive thermal anomaly on the western slopes of the mountains. These various
gold deposits and their well-constrained structural and tectonic settings can be
used as analogues for larger, deeper-eroded mesothermal gold deposits in the
Mesozoic Otago Schist belt. High level Miocene veins in NW Otago have formed
beneath the main divide of the initiating Southern Alps. Late metamorphic
gold-bearing veins formed as fluid escaped from the ductile-deforming crustal
root beneath Mesozoic mountains.