Mercur district

Region West, Southwest
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Outline of Mercur District from Krahulec (2018b), expanded to include the West Dip district.
Identified resources Identified resources of gold; historical production of gold and mercury.
Production 2,605,037 ounces Au along with 1,183,724 ounces of Ag and 3469 flasks of Hg (Krahulec, 2018b).
Status Past mining (Mercur closed in 1997); current exploration and reevaluation.
Estimated resources 1996 Demonstrated in situ reserves at Mercur: 3,377,000 mt ore @1.85 g/mt Au.
Geologic maps Clark and others (2012), scale 1:62,500.
Geophysical data Inadequate Rank 4 aeromagnetic coverage.
Favorable rocks and structures Mississippian thin-bedded, calcareous, sandstone and siltstone in the Mercur member of the Great Blue Limestone.
Deposits Mercur (MRDS dep_id: 10179493), Sacramento mine (MRDS dep_id: 10042246), and Marion Hill are the largest open pit mines.
Evidence from mineral occurrences MRDS; UMOS (Utah Geological Survey; 2021).
Geochemical evidence Alteration associated with the gold ores in the Mercur district typically is the extensive silicification (forming jasperoid) at the base of the Mercur member. The most common minerals associated with the gold ore in the Mercur district are pyrite, marcasite, orpiment, realgar, barite, stibnite, cinnabar, and a few very rare thallium minerals; thus gold ore was enriched in As, Ba, Hg, Sb, Si, and Tl.
Geophysical evidence Unknown.
Evidence from other sources See Krahulec (2018b).
Comments Gold mineralization in the Mercur district is concentrated near the crest of the Ophir anticline and localized near an east-northeast-trending set of normal faults. Individual gold deposits occur as lenses associated with decalcification on carbonate minerals and clay alteration of the limestone host rocks.
Cover thickness and description Exposed at the surface.
Authors Albert H. Hofstra.
New data needs Aeromagnetic and aeroradiometric surveys.
Geologic mapping and modeling needs None requested at this time.
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and radiometric surveys.
Digital elevation data needs Lidar complete.