THE OCCURRENCE OF GOLD AT SHUIYINDONG CARLIN-TYPE GOLD DEPOSIT,GUIZHOU

In this study,an electron microprobe analyzer(EMPA) was used to map the spatial distribution of gold and submicron to micron size visible gold particles in arsenian pyrite in a high grade ore sample from the Shuiyindong Carlin-type gold deposit,Guizhou,China.The samples studied were hosted in Permian bioclastic ferroan limestone of the Longtan Formation and showed evidence of decarbonation,silicification and sulfidation and was deposited in two stages.The results showed that there are two occurrences of gold in arsenian pyrite.One is invisible gold in arsenian pyrite with detectable Au(400 to 3800 ppm) and the other is comprised of sub-micrometer to micron size(0.1-6 μm) gold particles that are occasionally present in the goldbearing arsenian pyrite edges.The results also showed that As and Au contents of arsenian pyrite plot in a wedge-shaped zone.On the basis of petrography data of the ore,the depositional processes of arsenian pyrite and gold at the Shuiyindong deposit were discussed.The Fe present in sulfide minerals was most likely derived from dissolution of ferroan minerals in the host rocks with sulfidation of the dissolved iron by H2S introduced by ore fluids,which is the most important mechanism of gold deposition in Carlin-type system.Finally,we proposed that the Fe-poor calcite and dolomite veins or veinlets associated with mineralization may be an effective pathfinder for exploration of nearby unexposed Carlin-type gold mineralization.