Eocene magmatism: The heat source for Carlin-type gold deposits of northern Nevada

The origin of Carlin-type or sediment-hosted, disseminated gold deposits of the Great Basin, the major source of gold in the United States, is poorly understood. We propose that Eocene magmatism was the heat source that drove the hydrothermal systems that generated these deposits in the Carlin trend and Independence Mountains in northern Nevada. This interpretation is base d on a strong spatial and temporal association of Eocene intrusive-volcanic centers with the gold deposits of this region. Our new work and published Ar-40/Ar-39 dates indicate that magmatism was particularly intense between 39 and 40 Ma throughout northeastern Nevada, especially in and around the a rea of gold deposits. Carlin-type deposits mag have formed preferentially d uring Eocene magmatism because it was (1) more intense in the area than oth er magmatic episodes, (2) somehow compositionally distinct, or (3) accompan ied by extension that promoted hydrothermal flow However, large-scale exten sion does not appear to have been a factor in generating Carlin-type deposi ts.