Overview
All mineral processing for the Porcupine mining operations is carried out at the Dome Mill. The current process plant was built in the early 1980s, with the original carbon-in-pulp (“CIP”) circuit being constructed in 1988. In 1995, a new crushing circuit, additional leach tanks, a new CIP circuit, as well as a second grinding line were added. In 2004, the process plant was expanded by adding a Rod Mill to B Circuit to handle mineralization from the Pamour open pit. Following the 2004 expansion, the plant flowsheet has remained relatively constant.
The Dome process plant consists of a three-stage crushing circuit and two parallel rod mill and ball mill circuits ahead of a single leach and CIP circuit. The plant has a permitted capacity of up to 15,000 tpd, and a current operating capacity of approximately 12,000 tpd. Operating capacity depends on the proportion of the feed sources but is approximately 3.9 Mtpa at the current feed blend with A circuit able to handle 3,300 t/d and B circuit 7,700 tpd. In the mid-2000s, the plant operated at 4.3 Mtpa with A circuit at 3,360 t/d and B Circuit at 8,400 t/d when processing Hoyle Pond, Pamour, and some Dome stockpile materials. Throughput reduced in 2022 to approximately 3.0 Mtpa due to maintenance issues that began that year. In 2024, total mill throughput totaled 2.90 Mt at an average grade of 3.26 g/t and average recoveries of 92.9% for 282,000 ounces. During the year, the mill continued to experience high levels of maintenance which contributed to lower than planned mill utilization and availability rates. The Company has identified a number of opportunities to increase these rates, reduce operating costs and enhance metallurgical recoveries in the mill.
The process plant operates 24 hours per day, 365 days per year and recovers approximately 92% of the gold in the combined mill feed.
