Limousine Butte Gold Deposits, Butte Valley Mining District, White Pine County, Nevada, USAi

Regional Level Types
Limousine Butte Gold Deposits	Deposit
Butte Valley Mining District	Mining District
White Pine County	County
Nevada	State
USA	Country

Structure: Black Metals Fault zone and other steeply-dipping fault zones.

Alteration: Rhyolite porphyry is argillized, adjacent sedimentary rocks are skarn-altered and jasperoidized.

Commodity: Ore Materials: gold

Deposit: The property consists of a hydrothermal gold system that exhibits alteration features related to sediment/structure hosted gold deposits found elsewhere in Nevada. Mineralization at the Limousine Butte property consists of disseminated, structurally controlled and skarn hosted gold deposits related to a large mineralized porphyry complex located beneath the valley floor. In addition to the gold potential, a substantive copper/gold porphyry is present at Limousine Butte. Prospect drilling (15 holes) in the 1960's and 70's indicates that it has minimum dimensions of 1.5 miles by 0.75 miles. The quartz porphyry intrusive with an associated sulfide-alteration system is centered below the western portion of the property and has altered and mineralized extensive portions of westerly dipping Mississipian sedimentary rocks. Broad zones of silicification, brecciation and hornfel/skarns are developed within shales and carbonates near the quartz porphyry intrusive. Jasperoid alteration is present within the same reactive rocks 4.5 miles to the east where they form outcrops along the range front. Anomalous gold and copper mineralization occurs within and adjacent to the intrusive such as: 1,000 feet grading 0.10 percent copper in hole BV-11 and 701 feet grading 0.019 opt gold in hole BV-10. Relogging of several holes in the porphyry system suggested a late gold system overprint crosscutting and replacing skarn altered sediments and hosted within argillized rhyolite.

Deposit type: Skarn Au

Development: Porphyry copper exploration by many exploration companies was carried out in the Limousine Butte project area from the 1950s through the1980s that drilled several zones of low-grade gold and copper mineralization. This work identified porphyry-related gold mineralization up to 0.070 opt Au and skarn style gold mineralization grading up to 0.19 opt Au in drill holes. During the 1980's the Alta Gold-Echo Bay joint venture mined approximately 130,000 ounces of gold from surface jasperiods via heap leach at the Golden Butte Mine adjacent to the northeast portion of the property.Nevada Pacific Gold acquired the property through claim staking in 1997 and began compiling all the historical geologic and geochemical data produced over this forty year period. Gulf Minerals first identified a porphyry/skarn type magnetic signature in Butte Valley with a high-level aeromagnetics survey in the mid-1950s. The Newmont/New Jersey Zinc Joint Venture first drilled the discovery in 1962. Bear Creek Mining later calculated the porphyry to contain a resource of 50 million tons of 0.6% copper which was covered by a 1500 to 2500 foot thick post-mineral slide block. Relogging of several holes in the porphyry system suggested a late gold system overprint crosscutting and replacing skarn altered sediments and hosted within argillized rhyolite. The best intercept in the skarn/porphyry consisted of 701 feet of 0.019 opt gold, in drill hole BV-10. A small gold resource of 91,000 ounces was produced from shale and jasperoid hosted dolomites at the Golden Butte Mine in the north part of the project area by Alta Gold from 1987-1989. Between the Golden Butte mine and the Butte Valley porphyry, several gold anomalies are present in the Paleozoic carbonate and clastic rocks that range in age from the Devonian Pilot Shale to the Pennsylvanian Ely Limestone. Exploration drilling and geologic mapping in the Golden Butte Mine area (Resurrection Ridge) has identified that gold was formed along the edge of an Eocene age volcanic filled graben or possible caldera margin. The graben contact fault is a "feeder fault", containing high-grade gold (30 feet of 0.260 opt) at the shale-dolomite graben fault contact. The strike extension of this fault, and the alteration associated with it, is at least six miles long. On April 1, 1999 Newmont Mining Corporation and NPG entered into a joint venture agreement to explore the Limousine Butte property. By June of 2002, Newmont had spent $1,048,220 on identifying and drilling twenty one sediment hosted gold targets within a 25 square mile area. Drilling by Newmont and NPG to date (2004) has defined six oxide gold mineral inventories containing 39.4 mt grading 0.016 opt gold for a total of 620,000 ounces of gold. In 2002, Newmont elected to sell back its interest in Limousine Butte and presently holds a sliding production royalty of 1.5% to 2.5%. Meanwhile, NPG continues to explore the project area having completed another round of drilling in 2003, intersecting additional high grade (20' @ 0.309 oz/t) and low grade (195' @ 0.05 oz/t) gold mineralization in the Resurrection Ridge area. Drilling is ongoing in spring, 2004. At Nevada Pacific Gold Ltd.'s Limousine Butte project, joint venture partner Newmont Mining Corp. is focusing on six new target areas of hese new targets, located about 5 to 8 miles south of the previously identified discovery areas drilled during earlier exploration campaigns of the joint venture, were identified through exploration work conducted by Newmont, which consisted of a high-definition airborne magnetic/radiometric geophysical survey, ground-based gravity geophysics, detailed geologic mapping, and in excess of 800 rock chip/stream sediment samples. Using all drill-hole information available, Newmont has estimated mineral inventories on five disseminated oxide gold zones identified to date at Limousine Butte. These five zones, located in the central to northern portion of the project, contain in excess of 620,000 oz of gold (estimated at a 0.006 opt Au cutoff and an average grade of drill intercepts above that cutoff).

Ore(s): Gold mineralization was formed along the edge of an Eocene age volcanic filled graben or possible caldera margin. The graben contact fault is a "feeder fault", containing high-grade gold (30 feet of 0.260 opt) at the shale-dolomite graben fault contact. The strike extension of this fault, and the alteration associated with it, is at least six miles long.

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Link to USGS MRDS:	10310428

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