Abstract:

Western Qinling orogenic belt is one of the hot spots for orogenic and Carlin-type gold deposits exploration in China, where a super large gold deposit called Liba has been found. After choosing the No.6 ore belt of Liba gold deposit as a case for systemically studying alteration mineral association, host rock alteration zoning and gold mineralization features, the authors sum up the alteration zoning mode of this type of gold deposit. Typical concentric zonal structure can be distinguished clearly, which shows that three alteration zones from inner to outer are pyritization silicificationsericitization zone, sericitization zone and chloritization zone.The altered mineral assemblages in each zone are pyrite+sericite+quartz±arsenopyrite±muscovite±tourmalinite±calcite, sericite+chlorite+quartz+pyrite±biotite and chlorite+biotite±sericite±pyrite respectively, and corresponding to the three alteration zones which are Au enrichment zone, Au mineralization zone and no Au mineralization zoneMigration of elements in alteration rock shows that alterations of wall rock and its zoning are resulted by hydrothermal fluid and rock reaction; Au mineralization occurs accompanied with mineral alteration, and mineralization of Au has a close relation to pyrite mineralization and disseminated silicatization.

Key words: Liba, orogenic-type gold deposit, alteration zoning mode, gold mineralization, element migration, wall rock