Robinson Mine, Robinson Mining District, White Pine County, Nevada, USAi

Regional Level Types
Robinson Mine	Mine
Robinson Mining District	Mining District
White Pine County	County
Nevada	State
USA	Country

Structure: Host rocks have been folded, faulted, and fractured. Mineralization follows fractures in some cases. Rocks in the are folded into na east-trending anticline with moderate to gentle dipping flanks, later intruded by pluton and cut by nomal faults.

Alteration: Most significant is the hydrothermal alteration from monzonite intrusion. The deposit generally follows the typical porphyry copper deposit model in the pattern of alteration and mineralization. Anhydrous skarn developed in sedimentary rocks adjacent to potassically altered quartz monzonite. Peripheral to this is a quartz-sericite alteration zone followed by a quartz-clay-pyrite zone. Lacally present are advanced argillic alteration and some formation of retrograde hydrous skarn.

Tectonics: Paleozoic Cordillerian miogeosyncline

Commodity: Ore Materials: chalcocite, chalcopyrite, molybdenite, copper oxides; chrysocolla, malachite, azurite, cuprite, native copper, bornite, sphalerite, galena, pyrite, magnetite chalcopyrite, argentite Gangue Materials: pyrite, sericite, clay minerals, fluorite, quartz, garnet- diopside skarn, magnetite, limonite

Deposit: The Ely (Robinson) porphyry Cu-(Au-Mo) deposit, Cu-and Fe-skarns, and precious metaldeposits were once part of a contiguous mineralized system of Cretaceous age that was cut up and rotated by Tertiary Basin and Range-type normal faulting. The Robinson deposit generally follows the typical porphyry copper deposit model in the pattern of alteration and mineralization. associated with emplacement of a quartz monzonite pluton. Additional oreodies formed in adjacent sedimentary rocks. Silty to sandy layers of the Chainman Shale provided initial permeability, enhanced by later faulting. At the Ada, Rob Roy, and Los Angeles deposits, ore formation occurred in a favorable zone bounded by massive Ely Limestone and impermeable Chainman black shales. These ore horizons are oxidized stratabound blankets of silica-clay-pyrite-rich material.

Deposit type: Porphyry Cu, skarn-related

Development: Gold and silver were first discovered in the area by Thomas Robinson in 1867-1868, who gave his name to the district. Other nearby gold properties were soon claimed and worked sporadically ubtil the end of the19th century. Copper was discovered here in the early 1870s, but insufficient demand, lack of transportation, low grade of the ore, and the difficulty in extracting the copper made it unprofitable to mine it. The abundance of low-grade copper ore interfered with the extraction of the gold and silver using the processes common at that time. In 1897, Charles D. Lane, from California , purchased the Chainman Mine and Mill on the hillside west of Mineral City. The town name was changed to Lane City and Lane spent $168,000 in the next two years on a water ditch, power plant, and cyanide plant to treat the oxide copper ore, but failed. An Eastern company bought the property and erected a second cyanide plant near the first one, but sulfide ore was encountered at 180 feet deep and the cyanide processes were ineffective on the sulfide ore; the mine shut down after just a few months of operations. The Chainman Mine properties then purchased by the Nevada Consolidated Copper Company but litigation stymied operations. On the opposite side of the canyon closer to Ely, the Ely Mining and Milling Company bought the Robinson Group and built a cyanide plant near the mine. Sulfides at a shallow depth caused that mill to shut down too. In 1900, Mark Requa, the son of a Comstock engineer, optioned the copper claims of Edwin Gray and Dave Bartley. His initial interest in the area was to build a feeder railroad to the Eureka and Palisade Railroad. However, the copper soon interested him and he organized the White Pine Copper Company in 1902, and soon solved problems related to metal extraction and transportation. About the same time, Thomas Kearns, David Keith and others organized the McDonald - Ely Company with D. C. McDonald as manager. The Giroux, Ely Mines, Chainman, Ely Central & Butte and Ely Mine companies merged with the White Pine Copper Company financed by Mark L. Requa and this organization became the Consolidated Copper Company, which prepared to build a smelter at McGill that would have a capacity to process 10,000 tons of ore a day. The Consolidated Copper Company led by Requa brought the Nevada Northern Railroad a distance of 150 miles from Cobre (near current Interstate 80) to Ely to transport the copper ore. On September 30, 1906, Mark Requa drove a copper spike made from Ruth Mine copper ore into the ground to celebrate the arrival of the train. With new management, cheap transportation, and more effective extraction processes, the copper deposits of Robinson were finally developed productively, and by 1907, when the smelter in nearby McGill was completed, thirty mining companies were in operation in the Robinson District. The first blister copper was shipped in 1908. The mine earned only $622,470 in the first year, but produced $6,561,787 worth of copper in 1909. Over the years, the Consolidated Copper Company developed the Richards, Alpha, Emma and Morris underground mines and employed about 1,200 men from World War I through the 1920s. Copper prices dropped to 5 cents per pound in 1932 initiating a decline that resulted in the closure of the Kimberly mines until January 1937. By 1941 there were again more than 1,000 men on the payroll and the skip was surfacing 9,000 tons of ore a day. The underground mines shut down in 1949 and by 1951 were converted into open pit mines. In 1958, Kennecott bought out Consolidated Copper Company's Robinson District copper mines, and the Kennecott Copper Company operated until declining copper prices forced closure in 1978. In that time, more than 4.5 billion pounds of copper were taken from the Robinson District. At that time, ore production capa After Kennecott shut down its copper operations in White Pine County, several other mining companies became interested in the Robinson district mines, more for their gold potential than for copper. Alta Gold and Magma Copper operated in the Robinson District from 1995 to 1996 and BHP operated from 1996 until 1999. Due to low copper and gold prices, BHP announced the closure of all of their North American holdings and laid off 462 employees in 1999. In 2004, the mine was acquired by Quadra Mining Ltd. who is reopening the mine (2004) to produce copper and gold. Quadra Mining Ltd. announced updated proven and probable reserves at its Robinson Mine total 146.3 million tons grading 0.687% Cu and 0.008 opt Au. Over 97% of the mineral reserves at the mine are in the proven category. Contained and recoverable copper at the Robinson Mine has increased from 1.67 and 1.38 billion pounds to 2.0 and 1.67 billion pounds respectively. The increased reserves add 2 years to the estimated 8 year mine life. Quadra began commercial production at Robinson on October 1, 2004, and produced 23.6 million pounds of copper and 10,490 ounces of gold in concentrate in the remainder of 2004.

Geology: In mid-Cretaceous time, Paleozoic miogeosynclinal sedimentary rocks were deformed into an overturned E-W-trending anticline whose upper limb was thrust to the southwest. The axis if the anticline was subsequently intruded by a composite quartz monzonite stock dated at 110 million years. Hydrothermal alteration and mineralization associated with emplacement of the pluton formed the Ruth porphyry copper-gold system. Basin-and-Range normal faulting successively down-dropped the upper portions of the system to the east. A post-ore rhyolite intrusive cut the system 30 million years ago.

Ore(s): The main influence on mineralizationi s the metamorphic aureole surrounding the porphyry intrusion, but mineralization also follows fractures in some cases.

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Link to USGS MRDS:	10310402