Geology and geochemistry of Carlin-type gold deposits in China

• Published in: Mineralium deposita 2002-04, Vol.37 (3-4), p.378-392
• Main Authors: Rui-Zhong, Hu, Wen-Chao, Su, Xian-Wu, Bi, Guang-Zhi, Tu, Hofstra, Albert
• Format: Article
• Language: English
• Subjects: Calcite; Cambrian; Carbonate rocks; Cratons; Geochemistry; Gold; Groundwater; Igneous rocks; Low temperature; Meteoric water; Mineralization; Organic carbon; Orogeny; Precambrian; Pyrite; Quartz; Sedimentary rocks; Siliceous rocks; Sodium chloride; Sulfides; Sulfur; Triassic
• ISSN: 0026-4598; 1432-1866
• DOI: 10.1007/s00126-001-0242-7

The Carlin-type gold deposits in China lie mostly near the margins of the Proterozoic Yangtze and Aba cratons. Submicron-sized gold in micron-sized arsenian pyrite is disseminated in fractured Cambrian through Triassic carbonaceous shale and carbonate rocks, and is associated with anomalous Hg, Sb, As, U, and Tl. Alteration typically includes silicification, argillization, and sulfidation. Aqueous fluid inclusions contain CO^sub 2^, have relatively low temperatures of homogenization (250-150 °C), and salinities (8-2 wt% equiv. NaCl) that typically decrease from early to later stages. The indicated pressures of 105-330×10^sup 5^ Pa correspond to depths in excess of 1.0 to 3.0 km, assuming hydrostatic conditions. The [delta]D values of fluid inclusions (-87 to -47[per thousand]) and the calculated [delta]^sup 18^O values for water in ore fluids (-2.1 to 16.2[per thousand]) reflect interactions between meteoric water and sedimentary rocks. The [delta]^sup 13^C values of calcite (-9 to 2[per thousand]) and [delta]^sup 34^S values of sulfides (-24 to 17[per thousand]) suggest that C and S were derived from marine carbonate (and organic carbon) and diagenetic sulfides (and organic sulfur) in the vicinity of the deposits. Geologic relationships and geochronologic evidence indicate the deposits formed during a late phase of the Yanshanian orogeny (140-75 Ma). These gold deposits share much in common with the Carlin-type gold deposits in Nevada, USA. Both occur in carbonaceous, pyritic, sedimentary rocks deposited on extended margins of Precambrian cratons. The smaller Chinese deposits are generally in more siliceous rocks and the larger Nevada deposits in more calcareous rocks. In both countries, the host rocks prior to mineralization were affected by contractional deformation that produced many of the ore-controlling structures and the deposits do not show consistent spatial or genetic relationships with epizonal plutons. However, the Nevada deposits show broad spatial and temporal relationships with shifting patterns of calc-alkaline magmatism. The ore and alteration mineral assemblages, residence of gold, geochemical signatures, paragenetic sequence, and fluid inclusions are remarkably similar, which indicates that the deposits formed from low salinity, moderately acidic, CO^sub 2^- and H^sub 2^S-rich fluids by similar processes at relatively shallow levels in the crust (