Mining in focus
much further south than was originally
thought. Traditional theory postulates
that water and hydrothermal events, or a
combination of the two, were the principal
transportation agents of the abundant gold
deposit in the Witwatersrand Basin.
According to McCarthy, there are three
gold basins in South Africa: the well-known
Witwatersrand Basin, the Bethlehem
Sub-Basin, and the Colesberg Sub-Basin.
“Research indicates that the distribution
of the Witwatersrand-type rocks is much
wider than what was previously thought,”
says McCarthy. “There are definitely
Witwatersrand-type rocks outside of the
Witwatersrand Basin in the Bethlehem and
Colesberg areas,” says McCarthy.
It is important to distinguish between
goldfields and gold basins. Where there
are clusters of deposits within a Basin,
they are referred to as goldfields, like the
basins,” says McCarthy. A few holes were
drilled in and around the Bethlehem area in
the early 1990s, when the mining industry
decided there was no longer a future for
deep-level mining, and no exploration
work has been done since. Moreover, no
work has been undertaken in the Colesberg
Basin. According to Theart, there is another
sub-basin in the Koster area of the North
West Province that is worth mentioning.
The Koster sub-basin has been explored by
Goldfields and other exploration companies.
McCarthy is at the forefront of a
movement that challenges traditional
thinking about the Witwatersrand Basin,
and has proposed, in a recent presentation
at the Africa Down Under Conference in
Perth, Australia, that South Africa’s gold was
transported into the Witwatersrand Basin by
glaciers, during a previous ice age, and that
therefore, the gold could have been carried
There is evidence of artisanal mine workings throughout the Witwatersrand Basin.
The Central Rand has been a prolific producer of gold for more than 100 years.
[24] MINING MIRROR MAY 2019
Central Rand Goldfield and the Klerksdorp
Goldfield, for example, each of which
supported numerous gold mines. Potential
new goldfields have been identified by
several top geologists within the traditional
Witwatersrand Basin, and those, according
to McCarthy, include an area near Kroonstad
in the Free State, and close to Ventersburg,
also in the Free State, both of which look
extremely promising. Both are also very
shallow. McCarthy is of the opinion that the
Evander Goldfield has been misunderstood.
‘We have only really mined half of that
Goldfield, the other half is untouched,” he
says. In addition, McCarthy’s model of glacial
movement might add another dimension
and could put the Bethlehem and Colesberg
basins on the map.
Resuscitating gold exploration
To revitalise the interest in gold mining
and exploration in South Africa, it is
imperative that we start to critically re-
examine existing theories on the formation
of the Witwatersrand gold deposits (like
McCarthy and others have done). We need
to re-assess the geological record contained
in the rocks, and then develop new theories
that might lead us to virgin ground that has
never been on the map. That will require
out-of-the-box thinking.
After years and years of studying the
Witwatersrand Basin, many questions
remain unanswered. According to Professor
McCarthy, we do not fully understand
the Basin and all the processes that
resulted in its formation. There might
be another gold basin in South Africa
waiting to be discovered, apart from the
other opportunities that current theories
have identified within what we know
as the Witwatersrand Basin. A better
understanding of how the gold got there
in the first place might shed more light on
where the rigs should be deployed.
“The arguments and controversies about
the origin of the gold have been raging since
mining started in the Witwatersrand Basin,
and we don’t have all the answers,” says
Swart. “What we do know is that there are
more complex reefs out there waiting to be
discovered,” he adds.
Theories like the one proposed by
Professor McCarthy need more attention.
Most South African geologists, and
Witwatersrand Basin specialists, are familiar
with the great debate and heated discussions
about placer gold, hydrothermal sources,
and a combination of the two, called the
modified placer-theory. Placer theory
proponents believe that the Witwatersrand
gold was deposited in gravel-bed streams
by means of flowing water. McCarthy, a
placer gold advocate all his life, believes that
the gold was delivered, along with copious
sediment, by ice age glaciers and deposited
as water from the melting ice, redistributed
the sediment, and concentrated the gold.
If this is the case, it could open a whole
new world for geologists, gold miners, and
explorers in South Africa.
www.miningmirror.co.za