Golden Sunlight

Overview

The 2,000 hectares Golden Sunlight gold mine is located in Jefferson County in southwestern Montana, USA some 55 kilometres east of Butte and eight kilometres northeast of Whitehall. The property lies on the eastern flank of a fault-bounded mountain range known as Bull Mountain.

Golden Sunlight began operations in 1982. It is mined by conventional open-pit methods. The ore treatment plant uses conventional carbon-in-pulp technology as well as Sand Tailing Retreatment (STR), designed to recover gold that would otherwise be lost in the process.

The mine was not in production in 2010 as it entered an extended redevelopment phase during 2009, but it re-started production during the first quarter of 2011 and managed to produce 62,000 oz during the year. Proven and probable mineral reserves as of December 31, 2011 were 487,000 ounces of gold.

Location

The Golden Sunlight mine is located in Jefferson County in southwestern Montana, 55 kilometres east of Butte and eight kilometres northeast of Whitehall. The property lies on the eastern flank of a fault-bounded mountain range known as Bull Mountain. The hearest perennial watercourses are located 2-3 miles to the south and east of the mining operation.

Montana is a state in the Western United States that features numerous mountain ranges. The economy is primarily based on services, with ranching, wheat farming, oil and coal mining in the east, and lumber, tourism, and hard rock mining in the west.

Butte is Montana's fifth largest city having a population of over 34,000 people. The city was first settled by silver and gold miners as mining was booming in the district. Copper mining started in earnest in late 19th century as new technologies like electric power emerged.  

The Upper Clark Fork River, with Butte at the headwaters, is America's largest Superfund site. This area takes in the cities of Butte, Anaconda, and Missoula.

Geology & Mineralization

Proterozoic (1.4 Ma), Belt Supergroup clastic sediments of the LaHood Formation (locally known as the Bull Mountain Group) are intruded by Late Cretaceous, multiple intrusive, alkaline to subalkaline porphyry system.

The Golden Sunlight gold-silver telluride deposit is primarily hosted by the Mineral Hill Breccia Pipe which is related to the Cretaceous intrusions. The Proterozoic LaHood Formation host the breccia pipe and display mineralization as stratabound sulphides and sulphosalts.

Gold as free, micron sized particles is disseminated through a 200 metre diameter breccia pipe in the Mineral Hill Orebody. In the East and Rattlesnake bodies gold is hosted in debris flow complexes resulting from the erosion of the Mineral Hill deposit; East is 600 x 200 x 75 m thick while Rattlesnake is 350 x 150 x 70 m thick, and both are oxidized. The North body is on the hanging wall of a fault and is 180 m long x 35 m thick and oxidized in its upper portion.

Metals were most likely derived from the intrusive system but there are chances that part of them were leached from the Proterozoic host rocks.

Mining & Operation

Golden Sunlight is mined by conventional open-pit methods. Mining is standard drill-blast-load-haul. Open pit mining removes between 60,000 tons to 90,000 tons of material per day.

Mining operations expanded in the east area to mine ore that is now economic to be mined at current high gold prices.

Pit and tailings impoundment containment wells water is used as makeup water for the mill circuit.

Processing

The ore treatment plant uses conventional carbon-in-pulp technology as well as Sand Tailing Retreatment (STR), designed to recover gold that would otherwise be lost in the process. Approximately 2.4 million tons of ore are processed every year.

 Mill was upgraded in the April 2009 to January 2011 interval to be able to process new types of ore sourced from the East Area pit.

Tailings impoundment No. 1 is no longer active and has been reclaimed. Tailings impoundment No. 2 is active.

Environment & Community

Golden Sunlight implemented a drilling and blasting reduction program in 2009 which decreased drill time, drill footage and explosive product, and transitioned to a gassed emulsion blasting product. This program has resulted in less blasting and a reduction in greenhouse gas emissions.

Closure program include pump, treat and discharge of pit and tailings impoundments drain-down and containment wells water.

Barrick is involved not only in reclamation and restoration of the Golden Sunlight mine lands but also helped the state to complete a decade-old reclamation project of a former mine located near Yellowstone National Park in Montana.