Controls On Tertiary Epithermal Gold-Silver Mineralization, Northern Black Hills, South Dakota
Jack A. Redden, 1990. "Controls On Tertiary Epithermal Gold-Silver Mineralization, Northern Black Hills, South Dakota", Metallogeny of Gold in the Black Hills, South Dakota, Colin J. Paterson, Alvis L. Lisenbee, Tommy B. Thompson
Download citation file:
Tertiary gold-silver deposits in the Lead-Deadwood area have been exploited almost as long as the Precambrian Homestake gold deposit. The deposits were first described by Irving (1904) who was able to visit and map many of the mines. Recent papers by Shapiro and Gries (1970), Norton (1989), Paterson et al. (1988), and Redden and French (1989) summarize and update data on the deposits. The major mines of the late 1800's-early 1900's were developed along relatively small, high-grade replacement deposits of dolomitic sandstone beds at one or more levels in the Cambrian Deadwood Formation. Ore extended laterally from obvious vertical feeder fractures or joints which were commonly referred to as "verticals". Some deposits were also influenced by the emplacement of igneous sills in the Deadwood Formation that acted as barriers or traps for hydrothermal solutions. Because mineralization was closely related to the vertical joints and the favorable host beds were of limited thickness, the Tertiary deposits were of limited size. Nevertheless, approximately 90,000 kg (3 million oz) of gold were recovered from such deposits by the time production essentially ceased about three decades ago.
With the major increase in gold price in the late 1970's and early 1980's, and the development of low cost open pit mining and heap leach processing, exploration was undertaken by several companies to determine whether there were low-grade, large, disseminated-type deposits which were amenable to low cost mining and leaching operations. At present four companies are operating open pit mines in this type of mineralization.