| Abstract: | In the 1990s, some median-large gold deposits have been discovered in several lead-zinc metalloge-netic belts (e.g. the Qinling lead-zinc metallogenetic belt, Shanxi Province and Gansu Province and the Qingchengzi lead-zinc ore field, Liaoning Province) in China. Gold deposits and lead-zinc deposits spatially co-exist in the same tectonic setting; lead-zinc orebodies are commonly located below gold ore bodies. The host rocks of lead-zinc ore-bodies are conformably overlain by those of gold ore bodies. The age of gold mineralization is obviously younger than that of lead-zinc mineralization. Preliminary geochemical research has demonstrated the following: lead-zinc mineralization took place in a marine sedimentary-exhalative system, which had the characteristics of a high fluid/rock ratio, a high salinity and a high halide activity; meanwhile, most of gold was transported into the low-temperature hydrothermal plume and primarily enriched in sediments. During later (magmatism-) metamorphism-tectonism, gold was remobilized and transported into the metamorphic fluid which had the characteristics of medium-high temperatures, a low fluid/rock ratio and a low activity of halide, and precipitated at a favourable structural site. Therefore, the co-existence of gold and lead-zinc deposits and the separation of gold from lead-zinc result from the differences of chemical composition and circulation of ore fluids in the same tectonic unit. This phenomenon can be used as an important criterion in exploration. |
