The indicated mineral resource estimate was updated to 92.8 million tonnes at 1.92g/t gold for a total 5.7 million ounces of gold, while the inferred resource estimate was upgraded to 26.5Mt at 1.61g/t gold for a total 1/4Moz of gold.  

The previous indicated resource estimate was 59.2Mt at 2.08g/t god for a total 3.9Moz of gold, and an inferred resource estimate of 22.5Mt at 1.22g/t gold for a total 879,000oz.

The new estimate was based on 192,000m of exploration drilling in 928 drill holes and the mineral resources were reported within a pit shell using a US$1,400 per ounce gold price and a cut-off grade of 0.6g/t gold.

B2Gold said it had included in the update the probable reserves at the start of Fekola's production of 49.2Mt at 2.35g/t gold containing 3.7Moz.

To test Fekola's resiliency to lower gold prices, the company also ran the pit shells using a lower gold price of $1,250/oz, which gave an indicated mineral resource estimate of 90.7Mt at 1.94g/t gold for a total of 5.7Moz of gold and inferred estimate of 16.6Mt at 1.58g/t gold containing 844,000oz of gold.

The new estimate is being used by B2Gold to design a new mine plan to establish new probable mineral reserves.

It is also carrying out an engineering study to evaluate larger mine fleet options and the expansion potential of Fekola's mill from the current 5.5 million tonnes per annum rate to throughput of 7.5Mtpa.

The company will compare the economics of the higher throughput capacity to a baseline throughput of 5.5-6Mtpa.   

"Given the capacity of the Fekola primary crusher, SAG mill and ball mill, and engineering work to date, the 7.5Mtpa throughput can be achieved with an upgrade of the existing ball mill circuit," it said.

B2Gold added that additional process equipment upgrades would also be required, with these being determined in the expansion study, along with capital and operating cost estimates.

The expansion study is expected to be completed by the end of the year, with the results to be used in the overall mine/mill expansion evaluation to optimise the economics of the larger, new Fekola mineral resource.

It will then write a technical report once it completes the expansion study.

B2Gold's shares hadn't moved much Thursday, edging up 1.13% to C$3.59 (US$2.74) per share.