Minrom Consulting was recently contacted by a well-known manganese mine in the Northern Cape to perform scope and execute a Mining Work Programme (MWP).

Scope and Mining Work Programme at a manganese mine in Northern Cape

Minrom Consulting was recently contacted by a well-known manganese mine in the Northern Cape to perform scope and execute a Mining Work Programme (MWP). Geologically the project is situated in the Maramane Dome consisting predominantly a dolomitic unit of the Cumpbellrand Subgroup. The western edge of the Maramane Dome is overlain by the Gamagara quartzites and shales of the Olifantshoek Group. Locally the Gamagara Formation unconformably overlies the Reivilo Formation dolomites (part of the Campbellrand Subgroup) forming a karstic basement. Further to the west the older Transvaal Supergroup occurs on top of the rocks of the Gamagara Formation, which have been thrusted along what is termed the Black Ridge thrust fault.

Location of the manganese deposits

The manganese ore units from part of the Gamagara Formation and typically occur along the unconformity and occur as brecciated karstic potholes and manganese ore with included pinnacles of the basement dolomite. The ferromanganese ore is primarily found on top of the Gamagara ridge and along the western side of the Gamagara hill into the valley a shallowly dipping tabular ferromanganese layer.

Figure 1 – Geological cross-section of the manganese deposits of the Western belt (adapted from Cairncross et al. 2007)

Resource delineation, partial definition and drilling programme

As part of the MWP a resource delineation, and partial definition, drilling programme was embarked upon which consisted of 42 RC drill holes and totalled 902 meters over a surface area of 140 000 m2. Two (2) areas were targeted for the drilling programme based on the geological mapping previous performed by Minrom. The purpose of the drilling programme was to delineate the manganese mineralisation and identify mineable mineralisation based on the mines current production and economic requirements. The RC drilling was used to estimate the grade and tonnage of material which is primarily above a grade of 26% manganese (as this yields a sellable product for this specific client).

Figure 2 – Drill location pits 1 and 2 with 3D representation of the orebody and the distribution of the manganese concentration

Figure 3 – Sample and site photographs

Significant manganese mineralisation of mineable grades found

It was concluded that the area contained significant manganese mineralisation of mineable grades (>26% Mn) with several pockets (or “potholes”) containing high grade manganese. The drilling also identified areas which were strongly affected by dolomitic pinnacle dilution which greatly assists in the mining planning and scheduling.

The presence of these dolomitic pinnacles indicates that additional drilling will be required to refine the grade and mining models. Minrom therefore recommended that additional drilling and sampling be performed on all target manganese areas. A subsequent drilling programme is underway, and Minrom is excited by the results so far.