Ore Potential of Carbonaceous Deposits of the Kumak Deposit (Southern Urals, Russia)

Gold ore mineralization within the Kumak ore field confined to the black shale deposits of the Bredy Formation (C1bd) was studied. It has been established that the gold ore mineralization within its limits is confined mainly to the units of quartz-mica-tourmaline metasomatically altered carbonaceous shales. Hand-specimen sampling of all varieties of rocks showed the industrial content of gold in them up to 6.5 g/t and stably high content of silver (up to 7.6 g/t). Gold here is predominantly finely dispersed and is associated with two main mineral associations: gold-bismuth-telluride and native gold intergrown with tourmaline. An analysis of the composition of gold grains showed that they belong to the high-grade type. According to their chemical composition, tourmalines belong to dravite and foitite and are close to those of orogenic gold and gold-sulfide deposits. The close intergrowth of thin acicular tourmaline and gold indicates the synchronism of their formation and allows us to attribute the manifestations of the Kumak ore field to the quartz-tourmaline ash formation.