Bullabulling Gold Ltd. has reported the results of a positive prefeasibility study (PFS) for its open-pit Bullabulling gold project, located 60 km west of Kalgoorlie, Western Australia. The PFS considers the re-start of mining in an area previously mined by Resolute Mining during the 1990s. The PFS indicates that the project is technically and financially viable, and Bullabulling is moving ahead with a definitive feasibility study, with a goal of completing the study and reaching a development decision by the end of 2013.
The Bullabulling PFS considers development of a 7.5-million-mt/y open-pit mining operation with a conventional carbon-in-leach processing facility. Gold production of 1.95 million oz is forecast over a mine life of 10.5 years, starting in late 2015.
Pre‐production capital costs are estimated at A$326 million, with a further A$20 million of operating costs to be incurred before production commences. Sustaining capital and closure costs amount to A$58 million over the life of the mine.
Average life-of-mine cash costs are estimated at A$1,145/oz. However, in the first three years of full production, 651,000 oz are targeted for production at a cost of A$891/oz, delivering capital payback within that period.
The Bullabulling PFS considers development of five separate open pits. The primary mining fleet consists of two 360-mt excavators and up to 18 haul trucks of 180-mt capacity. It is assumed that mining will be undertaken by contractors.
The PFS estimates that 30% of oxidized material plus back fill within historic pits, together equating to approximately 11% of all material mined, can be free dug. The remainder will require blasting prior to excavation. Blast holes are sized at 229 mm dia in bulk waste and 165 mm dia in ore zones on benches 10 m high throughout.
The PFS mine plan calls for removal of approximately 283 million mt of waste rock, resulting in a strip ratio of 3.6 to 1.
Bullabulling processing will be carried out in a conventional carbon‐in‐leach plant. Run-of-mine ore at an average grade of 0.87 g/mt gold will be crushed in a single 42‐65 gyratory crusher. The grinding circuit consists of a 10.2-m-dia, 11-MW SAG mill operating in open circuit, with a pebble crusher reducing oversize mill discharge. A 7.9-m-dia, 15-MW ball mill operating in closed circuit achieves a final grind size of 80% passing 90 μm.
Five leach and five adsorption tanks, each of 4,050 m3 capacity, provide a total leach and adsorption residence time of 24 hours. Acid washing and elution of loaded carbon will be performed in separate columns using the split Anglo American Research Laboratories (AARL) process.
Carbon‐in‐leach plant discharge will be thickened using a 34-m-dia, high-rate thickener prior to deposition in the tailings storage facility.
The study lists principal project infrastructure consisting of access roads, a 142-person accommodation facility, borefield, tailings storage facility, and electrical power supply.