矿床地球化学国家重点实验室知识库

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 CO₂, 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 105–330×10⁵ Pa correspond to depths in excess of 1.0 to 3.0 km, assuming hydrostatic conditions. The δD values of fluid inclusions (–87 to –47‰) and the calculated δ¹⁸O values for water in ore fluids (–2.1 to 16.2‰) reflect interactions between meteoric water and sedimentary rocks. The δ¹³C values of calcite (–9 to 2‰) and δ³⁴S values of sulfides (–24 to 17‰) 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).