An approach to the metallogenic mechanisms and genesis of the gold deposits in the Jinpingshan area, Sichuan

The metallogenic mechanisms and genesis of the gold deposits in the Jinpingshan area, Sichuan are treated on the basis of geology and wall-rock alteration of the representative gold deposits. The ore-bearing wall rocks of the gold deposits in this area are mainly made up of epimetamorphosed Triassic silty schists, and subjected to widespread carbonatitization including ankeritization in the early stage and silicification characterized by beresitization, chloritization and quartz veins. The carbonatitization appears in the siltstones within the contact zone of carbonatite veins and muddy siltstones, and resulted from the muddy minerals in the hydrothermal metasomatic rocks during the emplacement of the carbonatite veins. The trends of the gold orebodies reconcile with the occurrence modes of the carbonatitization zones, and the gold is enriched in the highly silicified and beresitized zones. The higher background values of gold in the carbonatitized strata indicate a mantle source of gold. The gold mineralization tends to occur in the silicified and beresitized zones and sulfide quartz veins, and resulted from the re-enrichment of the element Au during the paulopost hydrothermal reworking in the study area. The gold deposits have gone through the early gold enrichment and the formation of the source rocks (beds) during the emplacement of the carbonatite veins and ankeritization, and large-scale gold enrichment during the hydrothermal processes represented by the sulfide quartz veins. It follws that the gold deposits in the study area are assigned to the hydrothermally reworked gold deposits.