Characterisation of the nonsulphide zinc ore at Huoshaoyun, Northwestern China, and its genetic aspects

The Huoshaoyun carbonate-hosted nonsulfide Zn deposit, in the Sanjiang-Tethys metallogenic belt of west China, is a newly discovered world-class deposit. Two ore bodies occur in the Longshan Formation limestone, in which the ore textures are mainly developed as laminated, banded, and brecciated. The metal minerals of the Huoshaoyun deposit are dominated by smithsonite and cerussite, with subordinate amounts of galena and siderite. Ore mineralization of this deposit is distinguished into three stages: sulfide stage, oxidation stage, and post-oxidation stage. Unlike most supergene Zn-Pb deposits, the Huoshaoyun orebody shows comparable ore grades for both Pb and Zn with an inverse supergene chemical zoning. Zinc is most abundant at the top of the deposit, whereas lead increases with depth. These two elements have different mobilities in solution, which implies that the primary source of zinc in the Huoshaoyun nonsulfide mineralization was originally located not far from the primary galena mineralization, the remnants of which are present in situ. Supergene zinc mineralization was derived from the dissolution of primary sphalerite hosted in the now-eroded rocks above the Huoshaoyun mine site. Zinc-rich solution migrated through the sedimentary host rocks, precipitated Zn minerals in pore spaces, and replaced detrital and hydrothermal alteration minerals.