Gold MineralisationGold mineralisation at Bendigo is believed to be synchronous with a major period of regional compression (crustal shortening) during which the Ordovician sediments detached from the underlying Cambrian oceanic crust. The increase in crustal thickness of the overlying Ordovician sequences through folding and thrust faulting is thought to have caused prograde regional metamorphism of the underlying Cambrian stratigraphy resulting in the formation and release of auriferous hydrothermal fluids. Fluids migrated up fault splays associated with major regional structures to be precipitated in nearby favourable low pressure dilation zones (e.g. faults, bedding planes, fold axes) created when the hydraulic pressure of trapped fluids exceeded lithostatic pressure during local seismic events.Known gold mineralisation is exclusively associated with quartz veining. Gold occurs as:Free gold in quartzIn association with sulphides in quartzIn association with fragments or laminae of wall rock in quartzAssociated with sulphides in wall rock adjacent to quartz veins.
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