Geological characteristics and metallogenic model of the Red Dog Pb-Zn deposit, Alaska, USA

Located in the De Long Mountains of the western Brooks Range, Alaska, USA, the Red Dog Pb-Zn deposit is a typical SEDEX (Sedimentary exhalative) or shale-hosted deposit and contains the largest reserves of zinc in the world. The ores are hosted in rocks of the Carboniferous Kuna Formation, which consists of black, organic-rich, siliceous mudstone and shale with locally abundant carbonate turbidites. The textural and compositional data for sphalerite suggest that the ore-forming process of the Red Dog Pb-Zn deposit consisted of four stages (the early brown sphalerite stage, yellow-brown sphalerite stage, red-brown sphalerite stage and late tan sphalerite stage) rather than comprising merely a single metallogenic event. Stage 2 and stage 3 seem to have been the main stages of mineralization. Mineralization was basically contemporaneous with the deposition of the Kuna Formation, together with the Mesozoic hydrothermal superimposition, as indicated by the isotope chronology and paleomagnetic studies. The formation of the ore deposit experienced four-stage sedimentary-hydrothermal process, i.e., deposition of barite and sulfides in unconsolidated muds; hydrothermal coarsening of barite and precipitation of sulfides; deposition of barite and sulfides in veins and replacement of preexisting barite; deposition of late breccias, fine-grained quartz and tan sphalerite.