Geochemistry and Metallogenic Model of Carlin-Type Gold Deposits in Southwest Guizhou Province, China

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Carlin-type gold deposits, also known as sediment-hosted gold deposits are among the largest hydrothermal gold deposits in the world, currently being sought and mined in the United States and China (Tretbar et al., 2000; Hu et al., 2002). The region of southwestern Guizhou (SW Guizhou), which is a region where the Carlin-type gold deposits were found for the earliest time in China, is an important component of the Yunnan-Guizhou-Guangxi “gold triangle” province. Carlin-type gold deposits in SW Guizhou, China, are hosted in late Paleozoic and early Mesozoic sedimentary rocks along the southwest margin of the Precambrian Yangtze craton. They can be classified as two types, i.e., the fault type and the strata-bound type, on the basis of their occurrence, shape and structural controls (Zhang et al., 2003; Xia, 2005). The former type includes the Lannigou, Yata, Banqi, Zhimudang (the upper orebodies), etc. with gold ores mostly occurring in high-angle compresso-shear faults. The ore-hosted strata are generally Middle and Lower Triassic in age, ore-bearing rocks are dominated by muddy siltstones and silty mudstones. The strata-bound gold deposits include the Shuiyindong, Taipingdong, Zhimudang (the lower orebodies), Getang, Nibao, etc. Gold ores are hosted mainly in the interbeded rupture zone at the karst discontinity surface of the Upper-Lower Permian and the Upper Permian strata. The deposits are mostly concealed ones at depth, the orebodies occur as stratiform, stratoid and lenticular ones and are developed along the strata, characterized by multi-layer distribution. Ore-hosted rocks are mainly impure bioclastic limestones and carbonate rocks in organic-rich coal series formations, with obvious anticline ore-controlling features. They have characteristics similar to Carlin-type gold deposits in Nevada, including notable enrichment in As, Sb, Hg, and Tl (Hu et al., 2002; Xia, 2005). Typical characteristics include impure carbonate or calcareous and carbonaceous host rock that contains disseminated pyrite and arsenopyrite. Gold occurs either as submicrometer-sized particles or invisibly as solid solution in As-rich rims of pyrite and arsenopyrite. Late stibnite, realgar, and orpiment fill fractures on the periphery of gold mineralization. Hydrothermal alteration caused decarbonation, silicification, argillization, and sulfidation, similar to Carlin-type gold deposits in Nevada (Hofstra and Cline, 2000; Emsbo et al., 2003; Kesler et al., 2003). Detailed studies in recent years have shed much light on the geochemistry and metallogenic mechanisms of the Carlin-type gold deposits in the