Geology Of The Annie Creek Sediment- And Porphyry-Hosted Gold Deposit
James F. Lessard, Thomas A. Loomis, 1990. "Geology Of The Annie Creek Sediment- And Porphyry-Hosted Gold Deposit", Metallogeny of Gold in the Black Hills, South Dakota, Colin J. Paterson, Alvis L. Lisenbee, Tommy B. Thompson
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The Annie Creek mine is a Au-Ag hydrothermal replacement deposit hosted within the Cambrian Deadwood Formation and in intermediate and alkalic Tertiary (40-60 Ma) intrusives. The deposit is located in a well-defined belt of Tertiary intrusives in the northern Black Hills. The reader is referred to Redden and Lisenbee (1990, this volume) for discussion on regional geology.
The Annie Creek deposit is located approximately 8 km southwest of Lead, in Lawrence County, South Dakota (Fig. 1). The deposit is on the western edge of the Portland mining district which is part of the larger Bald Mountain mining district. Production from the Portland mining district between 1877 and 1959 is estimated at a minimum of 24,335 kg (785,000 oz) gold and 65,100 kg (2,100,000 oz) silver; the Annie Creek mine produced approximately 837 kg (27,000 oz) gold between 1906 and 1916 (Shapiro and Gries, 1970).
In 1983, Wharf Resources initiated production from the Annie Creek deposit and produced 1953 kg (63,000 oz) gold by the end of 1989. Approximately 775 kg (25,000 oz) gold remain to be mined before the pit area is backfilled in the mid-1990's.
Mining is concurrent at the adjacent Foley Ridge mine, where similar sediment- and porphyry-hosted gold deposits occur (Fig. 2). The ore at both locations is mined by open pit methods, and gold is produced by heap leach/carbon adsorption recovery. Together, Wharrs Annie Creek and Foley Ridge mines have produced over 7750 kg (250,000 oz) gold.