Anorogenic felsic magmatism, rift sedimentation, and giant Proterozoic Pb-Zn deposits

The giant lead deposits that developed after ∼1.8 Ga in Australia, North America, and Africa are absent in the earlier geologic record. These Proterozoic lead (+ zinc) deposits were all preceded by major outbreaks of anorogenic felsic magmatism that brought significant amounts of lead-rich material (>30 ppm) to the surface of Proterozoic cratons. Erosion of these volcanics apparently transferred major quantities of the lead to rift basins where giant lead deposits were generated. All known giant Proterozoic sediment-hosted lead-zinc deposits (more than 50 Mt of lead metal) are explained by a model that is supported by Sm/Nd data relevant to mantle separation ages of volcanics and the metasedimentary source rocks for the lead ores.