French mining company Eramet’s Gabon-based subsidiary and manganese miner Compagnie Minière de l’Ogooué, (Comilog), together with the Gabonese government and its state-owned mining company Société Equatoriale des Mines (SEM), have partnered to undertake a strategic review of the Maboumine niobium and rare earths project to evaluate how to best develop it. Chantelle Kotze writes.
The project is one of many currently being undertaken in the Central African country to rebalance its largely oil and gas driven economy to a more natural resource diverse economy.
Located near Lambarene in central Gabon, the world-class Mabounié polymetallic ore deposit has, since 2005, been developed by Maboumine, a company owned partly by Comilog (76%), the Gabonese state (15%) and other minority shareholders (9%), under the leadership of Eramet, in partnership and with the strong support of Gabonese authorities and local communities.
The Gabonese state acquired the second largest stake (15%) in the project in 2014, as a means to add to its investment portfolio for the benefit of the Gabonese minerals sector.
In an exclusive interview, SEM CEO Fabrice Nze-Bekale notes the extensive development effort carried out so far has enabled the establishment of a sound knowledge of the deposit while developing an innovative and bespoke metallurgical process able to recover most of the value metals embedded in the ore.
The deposit was historically explored for phosphates some 20 years ago by SOMIMO (Société Minière Du Moyen Ogoué) – a JV between the State and foreign investors that was formed in 1992 to investigate phosphate mining potential in Gabon.
The deposit was subsequently acquired by Eramet, which through its subsidiary Comilog, explored the deposit for rare earths and niobium for more than 10 years. During this time Eramet and Comilog carried out several exploration drilling surveys – drilling more than 1 000 holes and extracting over 40 kg of ore.
Moreover, extensive geotechnical and hydrogeological surveys have also been performed inside and outside the deposit to validate project site selection.
“The Mabounié deposits’ ore mineralogy is complex but well understood,” says Nze-Bekale, adding that the niobium is contained mainly in complex to process pyrochlore and ferrocolumbite rock, and rare earths hosted in pyrochlore, apatite and crandallite.
Maboumine benefi ts from a very favourable rare earths distribution compared to other projects with a high content of “magnet rare earths” including neodymium and praseodymium – two rare earth metals higher in value because of their magnetic properties.
The Mabounié ore deposit is rich both in size (>$US50 billion) and concentration ($1 400/t). “It is arguably one of the most attractive known deposits, in the high value metals sector,” says Nze-Bekale. The Mabounié ore deposit has indicated mineral resources of 2.3 Mt of niobium petoxide (Nb2O5) grading at 1.2% and a rare earths mineral resource of 2 Mt of rare-earth oxides (REO), grading at 1%.
These mineral resource estimates, which were independently certified in 2015 by Canada-based mineral resource estimation company SGS Geostat, exclude the certifi ed Nb2O5 and REO resources (500 000 t and 600 000 t) present in the phosphate layer of the deposit which contains 20 000 t of phosphate (P2O5) grading at about 20% phosphate.
The current mine plan for the 361 km2 Mabounié polymetallic ore deposit is to first exploit the well understood rare earths and niobium. “We plan to later on evaluate the potential of exploiting the phosphate that lies at the bottom of the deposit, if viable,” says Nze-Bekale.
He notes that because the project will require a substantial amount of money to bring it into production, the strategic review of the project currently underway entails identifying possible technical and financial partners to help realise its development.
“Additional work as part of the review must be undertaken in order to refine the commercialisation of the project, while reducing the associated risks,” he explains.
In that context, Maboumine is now looking for partners able to bring the technical capabilities and fi nancial resources required to turn the deposit into a successful commercial venture.
An innovative hydrometallurgical process for the treatment of the Mabounié polymetallic ore has been developed by Eramet through a rigorous research and development process and the involvement of several international laboratories. Five process patents including a fluorinefree niobium/tantalum purification process, have been developed for possible use on the deposit.
Nze-Bekale explains that the Maboumine project’s economic potential was evaluated through a project scenario considering the construction of an integrated industrial complex at the Mabounié site. “The studied scenario was based on a conventional open pit and low strip ratio mine designed for an initial 20 year life-of mine extendable to 40 years,” he explains.
It is also based on the treatment of about 2 Mtpa of raw ore produced at the mine and treated in the benefi ciation section, generating approximately 1 Mtpa of ore concentrate, which is then processed in the hydrometallurgical plant to recover niobium and rare earths.
Based on this, approximately 1.1 Mtpa of reagents (limestone, sulphur, caustic soda) would be required in the process plant. The process scenario, backed by over 5 000 laboratory experiments and continuous pilot campaigns equivalent to 99 continuous weeks since 2010, has demonstrated recoveries of about 90% of niobium and rare earth oxides as commercial products.
Growing Gabon’s mining sector
Formed by a presidential decree in 2011 to facilitate the development of Gabon’s mineral resources and to manage the participation of the Gabonese state in mining projects, SEM has been undertaking exploration at its four gold exploration projects, namely the Kolissen and the Mavenza gold projects in the Moyen Ogooué province; the Pana gold project in the Ogooué-Lolo province; and the Camp 6/Miamizez gold project in the OgoouéIvindo province.
It also has three quarry exploitation permits: one permit in the Nyanga province for marble as well as two permits in the Estuaire and Moyen Ogooué provinces for aggregate.
Moreover, SEM is actively partnering on the development of other local mining projects. In doing so, it has recently signed agreements with two local gold miners with the view of developing their projects.
SEM has signed an agreement with a local mining company – Gabon Gold Mining – to obtain a 15% stake in its gold project, which is located in a goldbearing area known as Ndangui, near Lastourville in the south of Gabon. It is also in negotiation with the shareholders of another local mine operator in the country to obtain a stake in its gold project, which is located next to Gabon Gold Mining’s deposit. MRA