West African gold producer Avesoro Resources has successfully increased the measured and indicated mineral resource at its New Liberty gold mine, in Liberia, to more than 1.1-million ounces.
“The completion of the infill drilling campaign at New Liberty has improved the confidence in the estimated tonnes and grade of a portion of inferred material located below the current designed pit floor and within a $1 300/oz pit shell,” says Avesoro CEO Serhan Umurhan.
He explains that the intercepts encountered during the drill campaign have either met or exceeded the company’s expectations and the company has been able to successfully convert 241 000 oz of inferred material into the indicated mineral resource category.
“This significant improvement in the confidence level of resources at New Liberty has led us to look at options for how best to maximise the project economics at the mine.”
Umurhan says the company is looking at options to include the possible transitioning from the current openpit-only mine plan to a smaller openpit combined with an underground operation.
“We are now starting prefeasibility study (PFS) level geotechnical and hydrological studies to confirm the assumptions used in our internal study and anticipate that we will have a full PFS level underground mining study completed during Q1 2019.”
He says, in addition to evaluating underground mining of the existing indicated mineral resources, the company has also mobilised six diamond drill rigs and started an underground focused drill programme of 33 000 m and 83 holes.
“These are targeting the plunging high-grade ore shoots, focused on the higher grade, higher margin underground ounces with a view to converting further resources into the indicated category in support of an underground mining scenario.”
Infill Drilling Programme
As previously announced, an infill drilling programme was completed at New Liberty in June, with the objective of upgrading a portion of the existing inferred resources located below the current planned openpit floor but within a $1 300/oz pit shell, to the indicated mineral resource category.
The programme comprised 55 inclined diamond drillholes averaging 350 m in length and totalling 19 500 m. This programme has resulted in the conversion of a substantial proportion of existing inferred resources to the indicated mineral resource category. An updated mineral reserve for New Liberty is pending the results of the recently commissioned PFS which will evaluate both openpit and underground exploitation options.
The company is currently evaluating the optimal approach for the future mining and exploitation of the New Liberty orebody in order to deliver strong positive cash flows.
The company says it is now considering modifying its current openpit mining plan to reduce future waste cutbacks from the life-of-mine plan, resulting in the transition from an openpit mining operation to a combined openpit and underground mining operation.
“Over the next two months, the company plans to complete a further 83 diamond drillholes in a 33 000 m underground infill drilling programme with the aim of converting a further portion of the 409 000 oz of underground inferred mineral resources located below the previously reported proven and probable mineral reserve into the indicated mineral resource category.”
Concurrently, the company says it has started a PFS, including both geotechnical and hydrological studies, to evaluate these scenarios. This PFS will take up to six months to complete and will draw on both in-house mining expertise and also underground mining consultants from mining consultants company CSA Global.
After completing this PFS level underground mining study, the company expects to report new open-pittable and underground mineral reserves for the New Liberty gold mine.
Ndablama Exploration Update and PFS
In addition to the completion in July of its 16 200 m 75-hole diamond infill drilling programme at the Ndablama deposit, located 45 km north-east of New Liberty, the company has recently embarked on a further 22-hole, 4 200 m programme with 11 holes completed to date.
The company indicates that the Ndablama infill drilling is designed to upgrade the classification of inferred resources to the measured or indicated categories, after which mine planning and optimisation studies can be undertaken.