Columbia-East Erickson Mining District, Tooele County, Utah, USAi

Regional Level Types
Columbia-East Erickson Mining District	Mining District
Tooele County	County
Utah	State
USA	Country

The Columbia-East Erickson mining district is in southeastern Tooele County, about 22 mi west of Eureka. The district has been a modest Pb-Mn producer. The Columbia-East Erickson mining district produced a small tonnage of Pb-Ag, Mn, and Fe ores sporadically from about 1871 to 1917, and total metal production at modern metal prices is estimated at $2.3 million. The Sharp Pb-Ag underground mine is the primary producer.
The Sheeprock Mountains are geologically situated in the Basin and Range Province of west-central Utah. The range is composed of a thick sequence of northeast-dipping Neoproterozoic Sheeprock Group quartzite, metaconglomerate, and slate on the northeast flank of the range intruded by the Miocene (20.9 Ma) Sheeprock granite on the southwest flank. The intrusion is a high-silica granite (Christiansen and others, 1991). The range has been rotated eastward by post-intrusive listric extensional faulting so that a deeper level of the early Miocene Sheeprock mineralizing system is exposed on the southwest and higher levels are exposed on the northeast. In general, the “lower” (southwest) half of the granite is medium grained porphyritic and the “upper” (northeast) half is fine-grained porphyritic (Richardson, 2004).
The 7.8-sq-mi, red, oxidized Sheeprock granite has a 1.4-sq-mi highly differentiated “white facies” core containing smoky quartz and blue beryl (Christiansen and others, 1991; Richardson, 2004). The granite has ilmenite, magnetite, muscovite, zircon, apatite, monazite, thorite, uraninite, fluorite, samarskite, and topaz as accessory minerals. There are also small pegmatites and aplite dikes. The “white facies” is known to be enriched in Be, Th, and heavy rare earth elements (Richardson, 2004). Beryl occurs as (1) disseminated grains, (2) rosettes of radiating crystals as much as 2 ft in diameter, (3) in tiny, but massive seams/ veins, and (4) in small aplite dikes and quartz veins. Minor danalite is also reported.
Narrow, northeasterly trending greisen veins (quartz, muscovite, fluorite, hematite, magnetite, galena, sphalerite, and rare topaz) host weak Sn-W (cassiterite-wolframite-huebnerite) mineralization cutting the granite (USGS Model 15c) (Christiansen and others, 1991). The northwest and southeast sides of the granite have been prospected for Cu-F-U ±W mineralization, and the area northeast of (“above”) the granite has primarily produced minor Pb-Zn-Ag-Mn (specularite) mineralization. Seven U.S. Geological Survey National Geochemical Database samples near the Sheeprock Granite assay over 100 ppm Sn.