Golden Sunlight Mine
Location: Jefferson County, Montana, United States.
Owner: Barrick Gold Corporation.
Ore Type: Breccia pipe.
Reserves: Golden Sunlight produced 86,000 ounces of gold in 2014 at all in sustaining costs of $1,181 per ounce1. Proven and probable mineral reserves as at December 31, 2014, were 127,000 ounces of gold2.
In 2015, gold production is expected to be 90,000-105,000 ounces at all-in sustaining costs of $1,000-$1,025 per ounce.
Geological setting & Mineralization
The Golden Sunlight gold-silver deposit is hosted by a breccia pipe that cuts sedimentary rocks of the Middle Proterozoic Belt Supergroup and sills of a Late Cretaceous rhyolite porphyry (Porter and Ripley, 1985; Foster, 1991a, 1991b). At depth, rhyolite porphyry forms the matrix for fragments of the pipe. Creation of the pipe appears to be related to emplacement of an underlying hypabyssal stock related to the sills. Crosscutting the breccia pipe are hydrothermally altered lamprophyre dikes that postdate the gold-silver ore; locally, these dikes may have created areas of high-grade ore in the breccia pipe near their margins. The timing of emplacement of various igneous rocks and the hydrothermal alteration related to mineralization at the deposit.
Gold and silver in the region was concentrated along northeast-striking, high-angle faults and shear zones, some of which cut the breccia pipe and along which lamprophyre dikes have been emplaced (Porter and Ripley, 1985). These structures are thought to be part of a regional, northeast-striking zone of crustal weakness that has been intermittently active from the Proterozoic to the present (Foster and Chadwick, 1990; Foster 1991a). Because some hydrothermally altered and mineralized lamprophyre dikes are preferentially emplaced along structures that cross-cut the breccia pipe, their relationship to mineralization of the breccia pipe has been ambiguous. Certainly their emplacement is later than that of the pipe, and the simplest interpretation is that lamprophyre emplacement postdates mineralization. But, because the northeast-striking shear zones, veins, and dikes contain high-grade ore in places, a mineralizing process was obviously continuing during emplacement of the lamprophyre bodies.
Since its beginnings in 1982, Golden Sunlight Mine has continued to add resources to extend the life of the mine. Currently, the Montana DEQ is conducting the environmental review necessary to grant permission for mining additional resources referred to as the North Area Pit and South Area Layback, which would extend the mine life into 2016. Additional exploration is ongoing north of the Mineral Hill pit site with drilling activity in the Bonnie/Microwave area. 2013 will bring its own mix of success and challenge, so it is important that we remain intently focused on continuous improvement. As we work to deliver safe and profitable gold production, we cannot lose sight of our long-range goals—community partnership, environmental stewardship and most importantly, the safety and health of our people. I thank everyone again for the warm reception and look forward to getting to know you better in the coming months.
Safety and Health
We made great strides in improving our safety record, an achievement we celebrated in March, when we received Barrick’s Excellence Award for Best Safety Performance. As of first quarter 2013, GSM has gone five and a half years, and 2.7 million employee hours, without a lost-time incident, and over a year without a medical aid treatment incident. We still have more work to do in order to achieve our goal of zero incidents. As with most things, safety starts and ends with leadership. I expect all of our employees to be leaders when it comes to ensuring safety and continuing to send all GSM employees and contractors home safe and healthy every day.
Golden Sunlight Mine was the recipient of the prestigious Bureau of Land Management (BLM) 2012 Mineral Environmental Award for our third-party ore processing and reclamation initiatives. Golden Sunlight Mine initiated the program to assist small miners to mill outside “ores” and to assist with legacy mine materials containing reasonable concentrations of precious metals. In presenting the award, the BLM stated: “The Golden Sunlight Mine has turned liabilities into environmental and economic benefit—greatly enhancing the quality of the environment, saving taxpayer dollars, and creating local jobs.”