Chukar Footwall Mine, Maggie Creek Mining Subdistrict, Carlin Trend, Eureka County, Nevada, USAi

Regional Level Types
Chukar Footwall Mine	Mine
Maggie Creek Mining Subdistrict	Subdistrict
Carlin Trend	Group of Mines
Eureka County	County
Nevada	State
USA	Country

A former Au-Ag-As-Sb-Hg-Tl-Ba-Pb-Zn-Cu-Mn-Ni mine located adjacent to the Gold Quarry Mine open pit, about 6 miles northwest of Carlin, Nevada. Discovered by the Newmont Mining Corp. in 2001. Operated only during the period 2003-2004. Owned and operated by Newmont, the Gold Company (2004).

Mineralization is a precious and base metal, plus non-metallic deposit of Oligocene age (Mineral occurrence model information: Model code 173; USGS model code 26a.1; deposit model name: Sediment-hosted Au deposit; Mark3 model number: 17), hosted in limestone (decalcified and silty) of Early Devonian (youngest) to Wenlock (oldest) in age, and part of the Roberts Mountains Formation. Controls for ore emplacement include Northeast-striking faults which allowed gold mineralization to deposit in silty limestone along the hinge and limbs of a northeast- trending anticline in the Chukar Footwall deposit. Unique to Chukar is the occurrence of visible gold along fractures. Local alteration types consist of silicification and clay alteration. At the Gold Quarry deposit, in the central Carlin trend, Heitt (1992) reported K/Ar dates ranging from 28 to 27 Ma from supergene alunite veins that crosscut and postdate gold mineralization.

Gold grains range from <0.1 to 10.0 microns in size and usually occur associated with microfractures or disseminated in microcrystalline cherty matrix. Au:Ag ratio ranges from about 2:1 in mill grade ores to 1:3 in leach grade ores.Commodity Info: Gold grains range from <0.1 to 10.0 microns in size and usually occur associated with microfractures or disseminated in microcrystalline cherty matrix. Au:Ag ratio ranges from about 2:1 in mill grade ores to 1:3 in leach grade ores.

Local rocks include platy limestone and limy siltstone, chert at base.

Regional geologic structures include decalcified, silty limestone units of the Siluro-Devonian Roberts Mountains Formation which are folded into a northeast-trending anticline in the Chukar footwall deposit.

Local geologic structures include the Roberts Mountains thrust, Good Hope Fault system, Gold Quarry fault, and other faults, which created a pervasive fracture system at Gold Quarry complex. Isoclinal folding of bedding is common.

The Chukar Footwall underground mine workings are collared in the southwest corner of the Gold Quarry pit. Three portals were driven into the walls of the open pit mine. Ore was mined using longhole-stope and cut-and-fill methods.

With a gold endowment of approximately 530,000 ounces, Chukar Footwall is a relatively small satellite deposit to the much larger Gold Quarry deposit, which contains a total of 24 million ounces in past production and current reserves and resources. In 2001, Chukar Footwall was reported to contain 278,000 tons of ore grading 0.49 opt Au proven, and underground probable reserves as well as an addtional 115,000 tons, 0.46 opt Au of mineralized material.

Exploration could eventually increase the mine life of Chukar, which was expected to be operating for 3.5 to 4 years. Deep drilling by Newmont Mining Corp. in 2003 in the Gold Quarry pit beneath the Dos Equis and Chukar deposits intersected mineralization that will be further investigated for potential pit expansion or underground mining.

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Link to USGS MRDS:	10310452

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References