Big River Gold said an oversize single-stage crusher that would replace the 3 Stage crushing circuit, and a 4500kW SAG mill larger than previously planned, have been inserted into a plant design option study by Wave International.

The equipment and engineering changes are designed to meet the requirements of a 2Mtpa throughput, but also leave the possibility open for an expanded plant capacity of 4Mtpa - the maximum Borborema project is currently permitted for.

The study's purpose was to find "the most efficient use of capital and that the design and equipment choice would not incur additional costs or prevent a seamless transition to any future possible expansions".

The use of a 4500kW SAG mill means that only an additional small ball mill would be needed to increase throughput up to 4Mtpa through the comminution circuit. No changes to the Borborema process circuit were proposed as part of the option study,

"We are very pleased with the results of the Option Study as it leads to a more efficient use of capital and a strong basis for future expansion studies. We also anticipate some encouraging outcomes as we move to establish more precision on the costings over the coming weeks," said Andrew Richards, executive chairman.

The company noted that capex estimates both for the revised plant circuit and the incremental cost of a possible expansion up to 4Mtpa throughput were "very attractive".

The option study projected a total capex of US$94.6 million including contingency of US$15 million. It estimated he incremental cost of plant, equipment and engineering required to increase the plant capacity to 4Mtpa at US$34.8 million including contingency of US$5.8 million.

The planned expansion is dependent on "ongoing studies and availability of process water," added the company.

The Borborema Gold project, located in the Seridó area of the Borborema province, has a mineral resource of 68.6Mt at 1.10 g/t Au.