Gryphon Minerals has completed an optimization and scoping study that adds a 1-million-mt/y carbon-in-leach (CIL) plant to its previously planned 2-million-mt/y Banfora heap leach project in southwest Burkina Faso. The study’s base case calls for initial development of the heap-leach project for a capital cost of $85 million, followed two years later by a CIL plant at a cost of $45 million, which could be funded with early cash flow from the initial heap leach operation.
Average annual gold production from the startup heap-leach operation treating oxide only material is estimated at 63,300 oz/y for first two years at cash costs of $665/oz. Adding the CIL plant at the end of two years increases production to about 130,000 oz/y at cash costs of $717/oz.
The study also considers the option of developing the Banfora heap leach and CIL operations simultaneously, which offers somewhat more favorable overall project economics but which would require raising more startup capital from current difficult capital markets.
Gryphon has initiated due diligence with Macquarie Bank Ltd. for project debt funding to support construction of the initial 2-million-mt/y heap leach operation.
The Banfora project has a total of 67.2 million mt of measured and indicated resources, grading 1.4 g/mt gold at a 0.5 g/mt cut-off and containing 3 million oz of gold. In-pit resources currently under consideration total 1.1 million oz. Recent grade control (5 m x 5 m) drill results from within the pit designs demonstrate continuity of mineralization and some exceptionally high-grade gold, including 17 m grading 8.2 g/mt and 14 m grading 64.6 g/mt gold.
The mineral resources are shallow, with 90% above 150 m vertical depth, and remain open at depth and along strike. The ore reserves for the heap leach operation are also shallow, with an average vertical pit depth of 50 m across the deposits
Under the scenario of bringing the CIL plant on line after two years of heap-leach operation, the heap-leach facility will process approximately 16 million mt of plant feed over an eight-year life at an average head grade of 1.1 g/mt gold. The CIL facility will process approximately 6.7 million mt of plant feed over a 6.5-year life at an average head grade of 2.54 g/mt gold.
Gryphon managing Director Steve Parsons said, “We are very pleased with the results of the studies, which demonstrate significantly enhanced project economics for the initial startup 2-million-mt/y heap-leach operation and additional 1-million-mt/y CIL expansion capacity. With the optimization and additional capacity studies completed and a granted mining permit in place, Gryphon can now move to completion of debt funding due diligence, which is one of the final hurdles to commencing development at Banfora.”