The upgraded and increased mineral resource estimates of mineral sands producer Base Resources’ 100%-owned Kwale project, in Kenya, will form the basis for the preparation of, and reporting on, the project’s update ore reserves over the next few months, the company says.
The updated mineral resource estimate is the product of new drilling, assaying and mineralogical testwork, bulk density testwork and updated resource estimation work, as well as 12 months of mining.
The project’s updated mineral resources represent an overall increase of 5% in total material tonnes and a 2% increase in heavy mineral tonnes for the combined central and south dune deposits.
These increases were achieved despite the depletion of about 360 000 t of heavy minerals as a result of mining done at the central deposit.
Excluding the impact of this depletion, the project’s material tonnes and heavy minerals tonnes have increased by 8% and 7% respectively on the previously reported mineral resources at the start of the project.
The company adds that the project’s Joint Ore Reserves Committee-compliant measured resource has also increased significantly, with material tonnes up 81%, while heavy minerals confidence increased by 88%.
The Kwale project comprises two areas, separated by the Mukurumudzi river, that contains economically viable concentrations of heavy minerals, namely the central and south deposits.
A third deposit, the Kwale north dune is not currently included in published resources, notes Base Resources.
The project was initially owned by Tiomin Resources, which conducted drilling in 1997, after which Base Resources acquired the mine and drilled out the central and south deposits during October to December 2010.
Base Resources carried out the drilling using primarily the reverse circulation aircore method through wallis drilling and a small number of hand auger holes.
Project Area
The rocks of the area where the Kwale project is located are essentially of sedimentary origin and range in age from upper Carboniferous to recent.
Three mineral divisions are recognised, namely the Cenozoic rocks, the upper Mesozoic rocks (not exposed on the area) and the Duruma Sandstone series, which give rise to the dominant topographical feature of the area – the Shimba Hills.
The Magarini formation was deposited during Pliocene times and consists of unconsolidated sediments derived from the Duruma Sandstone series.
The Magarini sands are believed to be of Aeolian origin, deposited as coastal dunes after conditions of intense erosion.
The Kwale project deposits are a subset of the Magarini sands – a belt of low hills running parallel to the coast, that is generally poorly stratified and contains a fraction of clay and silt of around 24% to 30%.
Heavy minerals, mainly ilmenite, rutile and zircon, are locally concentrated within the Magarini sands giving rise to deposits such as Kwale central and south.