Lakeside Mining District, Tooele County, Utah, USAi

Regional Level Types
Lakeside Mining District	Mining District
Tooele County	County
Utah	State
USA	Country

The Lakeside mining district lies 50 mi west-northwest of Salt Lake City and just west of Great Salt Lake in northeastern Tooele County. The district was organized in 1871 and became a modest Pb producer. The main periods of metal production were the early 1870s, 1917 to 1924, and 1932 to 1948. Total district metal production at modern metal prices is estimated at $2.7 million. The Monarch underground mine at the north end of the district is the largest producer, probably responsible for 90% of the production (Perry and McCarthy, 1977).
The Lakeside district covers the southern half of the Lakeside Mountains of the Basin and Range Province in northwestern Utah. District production has been predominantly Pb ore (about 13,000 tons) in the north and siliceous iron ore in the south. There are no known intrusives in the range or any magnetic anomalies suggesting any intrusive rocks at depth.
The largest producer is the Monarch Pb replacement deposit in Cambrian- and Ordovician-age carbonate rocks. Orebodies in the Monarch mine typically occur along northerly trending fault systems. The ore is mostly oxidized with only remnant galena and sphalerite. There are reports of thick sections of low-grade Pb ore in the workings which have not been shipped due to the lack of associated precious metals. A 100,000 tons low-grade Pb-Zn subeconomic inferred resource is reported at the Monarch mine (Doelling, 1964; Perry and McCarthy, 1977).
The Lakeside district is unlike the many intrusive-centered base metal replacement camps in the eastern Basin and Range because it lacks associated igneous phases and has low precious metal credits. The low Ag:Pb ratios in the Lakeside district are similar to Mississippi Valley-type Pb-Zn ores. The Promontory Zn district on the east side of Great Salt Lake also has very low Ag:Pb ratios.