Characteristics,Genesis And Prospecting Indicators Of The Jiaochong Gold Deposit,Tongling,Anhui Province

The Jiaochong Au deposit is located in the Shizishan ore-field,Tongling,Anhui province.It is a unique gold deposit of skarn-type combined with Au-bearing sulfide-type.A detail geological,petrological,mineralogical and geochemical study has been carried out on the Jiaochong deposit,with a focus on analysis of its genesis.The field geological investigation indicates occurrence of skarn and Au-bearing sulfide types of ore bodies in the Jiaochong mine.The skarn-type of Au ore bodies occurs in the contact belt between dioritic porphyry and carbonate wall rock,while the Au-bearing sulfide-type of ore bodies exists in carbonate wall rock and penetrates the dioritic porphyry.The latter is inferred to be possibly related to pyroxene diorite.Ore in the skarn-type of ore bodies can be divided into spotted and vein-net vein types.It consists of skarn mineral + Fe-Cu-Pb-Zn sulfide + quartz-carbonate,showing an alteration and mineralization zone of contact replacement.The ore has granular,included,exsolution of solid solution,and replacement remnant textures,and vein to veined-network,mottled,and spotted structures.The mineralization process can be divided into early skarn,late skarn,quartz-sulfide and carbonate stages.Ore in the Au-sulfide-type of ore bodies can be divided into dense massive and vein types.Its mineral assemblage is Fe-As sulfide + Fe-Cu-Pb-Zn sulfide,indicating a mineralization zone of ore pulp cooling and crystallization.The ore indicates granular and emulsion textures,and dense massive,vein,and banded structures.The mineralization process can be divided into Fe-As sulfide,Fe-sulfide,and Cu-Pb-Zn sulfide stages.The ore deposit geological and geochemical data support the formation of the skarn-type Au ore deposit by the contact metasomatism after emplacement of the dioritic magma into the carbonate strata,and the generation of the Au-bearing sulfide-type Au ore deposit by magma liquation after emplacement of the pyroxene dioritic magma into the carbonate strata.The ore deposit prospecting indicator involves six aspects: strata,tectonics,magmatic rocks,alteration,mineralogy andgeochemistry.The interlayer fracture zone and contact zone and the pyroxene diorite and diorite porphyrite are the most important ore deposit prospecting indicators.