Abstract
Before the discovery and subsequent exploitation of the Kalahari Manganese
Field, the Postmasburg Manganese Field (PMF) represented one of the largest
sources of manganese ore worldwide. The PMF area has been actively mined
workings. The region comprises a Western Belt with ferromanganese (MnFe)
ore and an Eastern Belt with siliceous manganese (Mn) ore. The ore of both
belts is associated with the Campbellrand Subgroup of the Late Archean/Early
Proterozoic Transvaal Supergroup and is closely associated with the pre-
Gamagara unconformity. Numerous academic and economic studies have
been completed on both belts of the PMF. However, it is not well known how
the ore types, and mineral associations, differ along the strik e of the various
belts, and how this can aid in identifying new minable targets along the belt
and potentially make old diggings economically viable again. The focus area
of the study occurs on the Western Belt which represents a recrystallised MnFe
wad deposited in karsts of the Reivilo Formation of the Campbellrand
Subgroup. The focus of this study is on the MnFe ore resource on the farm
Paling, which is located 20 km north-west of the town of Postmasburg in the
Northern Cape Province of South Africa. The farm hosts an MnFe ore body
which is characteristic of the Western Belt of the PMF.
In 2019, PMG Mining (Pty) Ltd. contracted 4Arrows Mining and Exploration to
undertake a feasibility study to evaluate the potential mining of the Mn ore at
Paling. This was to be completed using reverse circulation drilling, as well as
diamond drilling on the farm Paling. These industry collaborators have provided
drill core and chip samples from this locality for this study. These samples were
investigated with the aim of characterising and determining the processing
characteristics of the Mn ore located at Paling. While previous work has studied
the PMF as a whole, this contribution is the first to focus on characterising
Paling Mn ore specifically, and the first to have drill core samples thereof. This
characterisation was completed using borehole logging, macroscopic
petrography, thin section reflected light microscopy and Scanning Electron
Microscope petrography. Major element geochemistry was determined through
ii
X-ray fluorescence analysis of ore samples. Magnetic susceptibility, abrasivity
and crushing work index tests were conducted on the ore in order to assess
the comminution and beneficiation characteristics of the ore.
Results showed that the ore package at Paling varies from 0 m to 22 m in
thickness, due to the irregular nature of the underlying unconformity. This study
identifies and characterises four ore types observed at Paling, namely massive,
vuggy, layered and conglomeritic ore. The ore minerals comprise
predominantly braunite and bixbyite with minor partridgeite and hollandite.
Gangue minerals are predominantly kaolinite, diaspore, and hematite. It was
found that the average MnFe ore is of a sellable Mn grade, provided the mining
cut does not include the overlying Doornfontein Member hematite
conglomerate, which does not contain Mn. The ore showed a positive response
to magnetic separation, which was found to separate g angue particles into the
non-magnetic fraction effectively, specifically in lower grade samples.
Abrasivity index and bond work index of the various ores did not highlight any
concerns for potential future comminution.
This study identified similarities and differences between the findings of
previous work on the PMF when compared to the ore at Paling. While the
majority of the stratigraphy and lithologies observed elsewhere in the region
were observed at Paling, there were some lithologies not present. Potential
issues for mining the ore were identified such as the irregular morphology of
the ore, but based on the ore characterisation completed during this study
found, none of the factors analysed would make the prospect unmineable.