Structural, mineralogical, and textural data from the Tarnagulla Goldfield demonstrate that the area has undergone three
significant phases of deformation. The first phase of deformation (Dl) predates the intrusion of the Tarnagulla pluton,
which has been dated using K/Ar as 391 5MY. We regard this pre-granite deformational event as the major regional
deformation. Gold-bearing quartz veins have been deposited in dilational sites on west-dipping reverse faults. These sites
demonstrate a geometry related both to faulting associated with Dl and the plunge of the Fl fold axes. This evidence,
together with chronology of unmineralised ? D2 and D3 faults, the absence of quartz veining associated with D3 events,
and the deformation of carbonate-quartz-biotite-sulphide aggregates within Sl by later S2, lead us to conclude that the
bulk of the mineralisation was essentially syn- or late Dl. S'80 values for fluids in equilibrium with vein quartz from
Central Victoria have indicated equivocal support for either a magmatic or metamorphic origin. Our evidence supports a
pre-magmatic origin for mineralisation at Tarnagulla and hence tends to favour a metamorphic fluid source.