Mining in focus
F
or more than a century, the origin
of the Witwatersrand gold in South
Africa has been the subject of
vociferous arguments and debates.
Generations of geological researchers
have burnt the midnight oil to explain the
phenomenon that continues feeding a ravenous
global demand for yellow metal. Despite these
years of research, and knowledge gained by
more than 120 years of non-stop mining, the
origin of South Africa’s gold deposits remains
uncertain. Today, the shallower portions of
the Witwatersrand Basin, where most of
the country’s gold is found, is a warren of
tunnels and stopes. Nonetheless, they continue
producing the goods.
More gold to be mined
Many believe that the Witwatersrand Basin is
reaching the end of its productive life, and that
it won’t be able to continue delivering the gold
on which the foundations of South Africa’s
most prosperous city, Johannesburg, and the
country’s economy were built.
The mainstream narrative is that gold
mining in South Africa is a sunset industry.
Most geologists with a good knowledge of the
Witwatersrand Basin, nonetheless, say that
half of the in situ gold has not been brought
to surface yet. The problem is not so much the
depth of the remaining reefs (which is true,
especially on the West Rand) or the low grades
of what is left (which is also true), but most
importantly, the lack of drilling holes in areas
previously not explored to the full.
According to an article authored by three
legendary South African geologists — Morris
Viljoen, Richard Viljoen, and Rodney Tucker
— the Witwatersrand contains six times
more gold than the world’s second-largest
goldfield. In an article titled “A review of the
Witwatersrand Basin — the world’s greatest
goldfield” that appeared in the June 2016 issue
of Episodes Journal of International Geoscience
(Vol. 39 No. 2: The great mineral fields of Africa),
they write that the Witwatersrand is a mature
goldfield with declining production, but that
there is still a significant amount of gold left
to mine.
“Much of the remaining resource occurs
at considerable depths. However, there are
still opportunities for extracting lower-grade
deposits at moderate to shallow depths. The
Basin thus remains a major exploration target,”
the article states.
Pursuing the low-hanging fruits
That there are shallow, low-hanging fruits
in and around the traditional mining areas
www.miningmirror.co.za
of the Witwatersrand Basin is a fact. One
doesn’t need to look much further than the
many artisanal workings that pockmark areas
previously deemed mined-out. The presence of
companies like West Wits Mining, Gold One,
and White Rivers Exploration is proof that
there is life in the reefs yet. Many potentially
shallow, productive deposits were sterilised
during the past 50 or so years, and West Wits
has showcased what can be done if a mining
company changes its mindset and pursues
lower-grade deposits, which are easier to mine
than deep and complex underground reefs.
White Rivers, on the other hand, is going after
deeper, potentially higher-grade deposits in the
Free State.
According to John Paul ( JP) Hunt, senior
exploration geologist at SRK Exploration
Services, the challenge is that most of the
remaining deposits are getting deeper,
which makes them more difficult to access.
“Furthermore, the grades become lower the
further one moves away from the primary
source areas into the more distal parts of the
depositional fan,” he says.
But apart from these deeper deposits, did
historical gold mining companies not leave
us with at least some pickings after their
insatiable feasts? (Not referring only to their
tailings, which DRDGold is competently
taking care of.)
Mark Wanless, partner and principal
geologist at SRK Consulting (SA), says that
there are indeed reefs that contain gold, and
which nobody has really exploited before,
mostly because of their low grades. To mine
these lower-grade reefs would be expensive,
and it would be a big ask to expect junior
mining companies to carry the cost burden
of developing the necessary infrastructure
to get the gold out. Mining companies have
historically mined through these lower-grade
reefs to get to the high-grade areas without
even reporting the lower-grade reefs. “So, I
guess that although we can say there is still
plenty of gold in the Witwatersrand Basin, we
have to ask whether it would make economic
sense to liberate the gold,” says Wanless.
Wits Basin has plenty to offer
Manie Swart and Rob Handley, geologists
at consultancy firm Shango Solutions,
agree that many gold-bearing reefs of the
Witwatersrand Basin are not yet depleted,
as is often reported. Both men have worked
extensively throughout the Witwatersrand
Basin on different projects for many years
and are convinced that there are reefs that
still have plenty to offer. There is a false
MAY 2019 MINING MIRROR [21]