Geology and geochemistry of the Mercur mining district, Tooele County, Utah

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:7017828

Tafuri, W J

The Mercur mining district is located in the southern end of the Oquirrh Mountains approximately 35 miles southwest of Salt Lake City, Utah. The gold deposits occur in the east dipping limb of the Ophir anticline and are confined to favorable beds in the Mercur Member of the Mississippian Great Blue Formation. Host rocks are thin bedded bioelastic limestones and calcareous siltstones. The mineralized zones are cut by extensive small displacement high angle normal faults. Gold mineralization forms stratiform and strata-bound disseminated ore bodies within the favorable beds. The apparent control of the mineralization is the porosity and permeability of the host rocks combined with strong fracturing caused by the faulting. Mineralization occurs in zones of hydrothermal alteration consisting of partial decalcification followed by the introduction of varying amounts of silica and organic carbon and slight amounts of kaolinite and sericite. Gold has been observed, in the sulfide zone, in three forms: as one to two micron sized inclusions in marcasite; as gold bonded with complex organic molecules; and, rarely, in the native state as grains less than 5 microns in size. Commonly occurring minerals associated with the gold mineralizations are; pyrite, marcasite, orpiment, realgar and barite. The introduced organic matter occurs as extractable hydrocarbons and as insoluble activated carbon. Gold is found in the asphaltene phase of the extractable hydrocarbons and in the activated carbon. Both the asphaltene and the activated carbon are thought to be degradation products of a more mobile petroleum precursor that circulated in the hydrothermal system. The degradation to asphaltene and activated carbon could have been due to the increase in temperature, increase in Eh and water washing as the hydrothermal system matured.

• Research Organization: Utah Univ., Salt Lake City (USA)
• OSTI ID: 7017828
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ASPHALTENES
ASPHALTS
BITUMENS
CLAYS
ELEMENTS
FEDERAL REGION VIII
GEOLOGIC DEPOSITS
GOLD
MATURATION
METALS
MINERAL RESOURCES
MINERALIZATION
NORTH AMERICA
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
PETROLEUM DEPOSITS
RESOURCES
SOURCE ROCKS
TAR
TRANSITION ELEMENTS
USA
UTAH