EVIDENCE FOR SYNKINEMATIC MAGMATISM AND MINERALIZATION IN THE NEOPROTEROZOIC SEDIMENT-HOSTED KENNECOTT RIDGEWAY AU-AG-MO DEPOSIT, SOUTH CAROLINA

The Neoproterozoic large tonnage, low grade, low sulfide Kennecott Ridgeway Au-Ag-Mo deposit has been described as a gold-rich volcanic-associated massive sulfide deposit, and interpreted as syngenetic exhalative mineralization overprinted by syntectonic deformation and epithermal alteration. Research through the CODES ARC Centre of Excellence in Ore Deposits at the University of Tasmania suggests that the deposit is of epigenetic origin, formed within a major north-dipping ductile-brittle deformation zone during a period of rapid tectonic evolution associated with collision and amalgamation of the Carolina and Charlotte volcanic arc terranes. The host rocks are dominantly immature turbidites the basal Richtex Formation. Mineralization was multi-phase, with cleavage-parallel auriferous quartz-carbonate-sulfide veins formed during early heterogeneous ductile deformation, associated with often intense feldspar-destructive quartz-sericite and propylitic alteration. Sulfidation of detrital Fe-Ti oxides along the coarse-grained basal layers of turbidite beds formed localized bedding-parallel pyrite + rutile concentrations previously interpreted as syngenetic. Late kinematic brittle deformation was accompanied by localized intrusion of volatile-rich aplite dikes and formation of aplite-cemented breccias, previously interpreted as felsic volcanic rocks. Magmatism was accompanied by silicification and often intense feldspar-stable potassic alteration with additional Au mineralization. The Ridgeway deformation zone may be a second-order structure rooted in the Carolina-Charlotte terrane suture zone to the north, and aplite intrusions and mineralizing fluids linked to anatectic stitching granites.