Spatial and Temporal Distribution of Au and Pb‐Zn Mineralization: Phenomenon, Mechanism and Implication

Abstract  In the 1990s, some median‐large gold deposits have been discovered in several lead‐zinc metallogenetic 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.