The Karangahake epithermal Au-Ag mine consists of two main lodes, the Maria
and the Welcome/Crown hosted in Miocene andesites. Mineralisation is strongly
constrained to major structures and is genetically linked to dynamic tectonic
processes. Two main periods of faulting are represented in the deposit:
1. NE striking right-lateral/normal oblique linked spatially and temporally
with the mineralising system, and
2. ESE striking right-lateral/normal oblique post-mineral faulting that
displaces the lodes.
Paleostress analyses performed on a limited kinematic data set indicate NW-SE
extension during the formation of the vein system. Veins and lodes strike NNNE
and accordingly contain a strike-slip component. The kinematics of vein
formation at Karangahake is broadly consistent with that of other deposits
within a NNE-trending belt of deposits. Oblique shear on deflecting structures
will create zones of compression and dilation. Dilatant zones created on steep
structures create fluid pathways potentially focussing large volumes of fluid
from deep parts of the system into dynamic structures.