Buckingham mine (Hardy mine; Bentley mine; O'Leary mine), Battle Mountain Mining District, Lander County, Nevada, USAi

Regional Level Types
Buckingham mine (Hardy mine; Bentley mine; O'Leary mine)	Mine
Battle Mountain Mining District	Mining District
Lander County	County
Nevada	State
USA	Country

Sec 30, 31 T32N R44E. Silver Lead.
Structure: Folding, thrust faults NW and ne-trending faults: buckingham fault

Alteration: There were four alteration events: 1. contact metamorphism of the host sedimentary rocks during emplacement of the granitic plutons 2. hydrothermal alteration associated with the metallization event 3. clay and sericite alteration associated with faulting 4. sugergene alteration

Tectonics: Calc-alkaline magmatic arc.

Commodity: Ore Materials: molybdenite, tetrahedrite Gangue Materials: pyrite, galena, sphalerite

Deposit: The Buckingham stockwork molybdenum system is classified as a low-fluorine (or quartz monzonite) molybdenum system by Theodore and Menzie (1984). It contains one of the largest identified resources of molybdenum in the United States, estimated at more than 1 billion tonnes of mineralized rock averaging approximately 0.06 weight percent molybdenite (MoS2) and containing 100 million ounces of silver as well as smaller amounts of tungsten, copper, and gold. Molybdenum mineralization is related to emplacement of a late Cretaceous (86-Ma) composite porphyry system that intruded and metamorphosed the surrounding Late Cambrian Harmony Formation to biotite hornfels. Approximately half of the Buckingham deposit is hosted by metamorphosed and intensely veined rocks of the Late Cambrian Harmony Formation and half by intrusive rocks (Doebrich and Theodore, 1996). Molybdenum mineralization is related to the emplacement of a late Cretaceous composite quartz monzonite porphyry system that intruded and strongly metamorphosed the enclosing Paleozoic sedimentary rocks to hornfels. There are at least seven major phases of intrusions that collectively form what are called the East and West stocks. All seven phases contain molybdenum mineralization. The main Buckingham deposit formed in association with five igneous phases located in the two stocks. All five phases developed shells of molybdenite mineralization and the shells locally overlap to produce grades of about 0.1 to 0.20 weight percent MoS2. Porphyry copper deposits in the copper zone surrounding the central molybdenum zone underwent supergene enrichment to create the Contention, Carissa, Copper Queen, Widow, and Sweet Marie copper deposits. Gold-silver skarn ore at the Surprise Mine and distal disseminated silver-gold ore associated with silica-pyrite alteration at the Empire Mine (approximately 1.5 million tonnes averaging 1.8 g Au/t) and at the Northern Lights Mine (approximately 390,000 tonnes averaging 1.6 g Au/t) may be associated genetically with the Buckingham system. There appears to be metal zoning from proximal copper-rich ores in the Contention Pit to the distal gold-silver-copper ores in the Surprise Mine (Doebrich and Theodore, 1996).

Deposit type: Porphyry Mo, low-F

Development: The historic mine was discovered in the late 1860s, but no record exists of early production. In 1912, the deposits had been developed by an incline and a crosscut 140 feet long, with 130 feet of drifts in the ore zone. Production was sporadic from 1913 to 1929. Workings on the Buckingham claim include an 850-foot inclined shaft with drifts on many levels. Recent exploration by a variety of companies has defined a large low grade molybdenum orebody centered in this area. The porphyry molybdenum potential of the prospect was first recognized in 1962 by Congdon & Carey exploration firm, whose drill holes only grazed the fringes of th e upper West stock molybdenite shell. In 1967, Union Pacific Mining Corp. drilling hit the moly mineralization and intersected it at successively greater depths eastward, tracing the Buckingham Fault. Under a joint venture with Climax Molybdenum in 1973-1980, more drilling tested moly mineralization in the East stock and outlined more mineralization southwest of Buckingham. Duval Corp explored the property in 1975-1982, defining a small reserve in the uppermost East stock molybdenite shell. Climax intensely studioed the deposit in 1980-82 as part of a pre-feasibility study, forming the basis for a detailed study and report on the deposit by the USGS in 1992. The property is currently held by Newmont with continuing delineation of the deposit.

Geology: In the historic workings, Hill reported that the hanging wall is a well-marked fracture filled with gouge, below which for 12 to 15 feet, the quartzite contains, disseminated pyrite, cut by small stringers of tetrahedrite sphalerite and galena for three feet below the hanging wall. The hanging wall ore carried considerable silver mineralization.

Ore(s): Molybdenum mineralization is related to the emplacement of a late Cretaceous composite quartz monzonite porphyry system that intruded and strongly metamorphosed the enclosing Paleozoic sedimentary rocks to hornfels. There are at least seven major phases of intrusions that collectively form what are called the East and West stocks. All seven phases contain molybdenum mineralization. The main buckingham deposit formed in association with five igneous phases located in the two stocks. All five phases developed shells of molybdenite mineralization and the shells locally overlap to produce grades of about 0.1 to 0.20 weight percent MoS2. Mineralization is also locally controlled by shear zones, faults, and fractures .

Other Databases

Link to USGS MRDS:	10310305

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References