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7473764 
Journal Article 
Fluid access and fluid-wall rock interaction in the genesis of the Archaean gold-quartz vein deposit at Hunt Mine, Kambalda, Western Australia 
Phillips, GN; Groves, DI 
1984 
389-416 
English 
Gold mineralization at the Hunt mine, Kambalda, is situated within a major steeply-dipping schist zone cutting a thick sequence of metabasalts. The overlying more ductile ultramafic rocks and, in places, pre-existing massive Fe-Ni-Cu sulphide ore, have acted as an effective barrier to fluid flow up the schist zone and led to preferential hydraulic fracture of the more competent metabasalt. An extensive set of quartz veins within the schist zone terminates abruptly at the contact with the ultramafic sequence, whether Fe-Ni-Cu sulphides are present or not. The fracturing and veining of felsic dykes within the schist zone, combined with their alteration (compatible with other wall rocks), suggest that such dykes have no direct relation to gold genesis. Fluid-wall-rock interaction has produced a series of alteration zones and auriferous quartz veins at Hunt mine. The pattern comprises a broad zone of carbonation in which calcic-amphibole and some chlorite are replaced by ankerite and calcite, a less extensive zone where biotite replaces chlorite, and an even narrower zone of pyritization adjacent to the quartz veins. CO2, S and K are the main added components. The formation of pyrite at the expense of Fe-Mg silicates has stabilized more-magnesian chlorite and biotite adjacent to the quartz veins, and also caused fluid reduction. High gold values are virtually restricted to the zone of pyritization. Fluid-inclusion data suggest that 300-350oC, H2O-CO2-rich fluids of low salinity were responsible for the Hunt hydrothermal alteration. These data, the alteration assemblages and the location of the gold suggest that gold, transported as reduced sulphur complexes, was deposited in response to fluid reduction and the lowering of total sulphur in solution, both a result of pyritization. The Hunt gold deposit was the result of hydraulic fracture of a more competent unit near a lithological contact, plus a chemically favourable host in which fluid-wall-rock interactions resulted in deposition of gold. Regional uplift appears to have been important in triggering hydraulic fracture in the Hunt mine environment. (Authors' abstract)-C.N.