Carlin-type gold deposits in Nevada—Critical geologic characteristics and viable models: Economic Geology, 100th Anniversary Volume

Carlin-type Au deposits in Nevada have huge Au endowments that have made the state, and the United States, one of the leading Au producers in the world. Forty years of mining and numerous studies have pro-vided a detailed geologic picture of the deposits, yet a comprehensive and widely accepted genetic model re-mains elusive. The genesis of the deposits has been difficult to determine owing to difficulties in identifying and analyzing the fine-grained, volumetrically minor, and common ore and gangue minerals, and because of postore weathering and oxidation. In addition, other approximately contemporaneous precious metal deposits have overprinted, or are overprinted by, Carlin-type mineralization. Recent geochronological studies have led to a consensus that the Nevada deposits formed ~42 to 36 m.y. ago, and the deposits can now be evaluated in the context of their tectonic setting. Continental rifting and deposi-tion of a passive margin sequence followed by compressional orogenies established a premineral architecture of steeply dipping fluid conduits, shallow, low dipping “traps ” and reactive calcareous host rocks. Sedimentary rock sequences that formed following continental margin rifting or in a foreland basin ahead of an advancing thrust front contain reactive pyritic and carbonaceous silty limestones, the primary host rocks in almost every deposit. The largest deposits now lie in the lower plate to the Devonian to Mississippian Roberts Mountai