Springbok Recce: Geology, Mining Heritage (and Wild Flowers)
By Peter Rosewarne
Figure 1 The Matzikammaberg at Vanrhynsdorp
This trip had its beginnings during the Lockdown with reading up on some books on South Africa’s mining heritage, geological sites and geological journeys. With the relaxation of travelling restrictions and reports of a bumper flower season in Namaqualand, I decided on the spur of the moment to do a trip to the Springbok area, which is rich in sites of geological and mining interest. My wife and I were going to go but, in the week we’d originally chosen, the temperatures were predicted to be down to zero overnight and the accommodation that we’d contacted was fully booked. The following week looked good weather-wise and accommodation was available so I decided to set off, alone this time and just as well because most of the sites visited would have been boring for a non-geologist or someone not into minerals, or birds. This account might be boring to you anyway but here goes… The photographs were taken by me but the facts and figures were taken from the references listed at the end of this article.
Getting there
The N7 used to be my favourite road in South Africa because there were no roadworks and it was usually pretty quiet once you got past Malmesbury all the way to the Namibian border. Then came the Citrusdal-Clanwilliam roadworks and then the Cape Town-Malmesbury roadworks to disrupt things. However, on my trip to Springbok on 6 September 2020 I was very pleasantly surprised to find that all is now just about done apart from some minor roadworks near Du Noon. It’s basically a dual carriageway all the way to and through Malmesbury now and a very good road all the way to Springbok. Many of you will have travelled this route or parts of it on the way to Namibia or to various geological sites.
The geology is mostly quite spectacular and enables you to pass through scenery sculpted from Recent-age sediments to Precambrian-age (>600 Ma) rocks. Leaving Cape Town, the Table Mountain Group (TMG, c.500 Ma[1]) forms a constant mountainous presence to your right while the road meanders over gently rolling hills formed from Malmesbury Group (c.600 Ma) shale, greywacke and phyllite. Elevated areas of more rugged hills comprise of granites of the Darling and Pardeberg plutons, part of the Cape Granite Suite (c.550-500 Ma), to your left and right fronts, respectively. Way over to the left you catch glimpses of Recent-age dune sands (still active) of the Witsand near Atlantis.
Approaching Piketberg you see the buildings and some waste rock dumps of the PPC cement works of De Hoek, with the active quarry of Soutkloof to your right. This quarry and the now closed De Hoek quarry are exploiting limestone lenses within the Malmesbury Group phyllites. After what seems like a long stretch of wheat fields on rolling Malmesbury Group sediments you start to ascend Piekenierskloof Pass and also start ascending through the lower formations of the TMG. The Piekenierskloof Formation comprises of shale and conglomerate and grades into the Peninsula Sandstone Formation which forms the rugged mountains that you cross before coming down into the Citrusdal Valley. You now have TMG rocks forming the mountains to your right and left while the valley bottom comprises of softer shale and subordinate sandstone of the Bokkeveld Group, with patches of white alluvium associated with the Olifants River. You are now squarely within the northern limb of the Cape Fold Belt.
After
leaving Clanwilliam behind, with its then (6 September 2020) overflowing dam,
you get onto rocks of the Gariep Supergroup (c.700 Ma), which are very similar
to those of the Malmesbury Group. The TMG still occupies the mountainous
terrain to the right and to a lesser extent to the left but you eventually come
out into a broad plain formed on Vanrhynsdorp/Nama Group sediments (550–530 Ma),
mainly shales. However, there are also some lenses of limestone and marble here
with a prominent road cutting through one by the Wideou River and a marble
quarry to the right and a last lense of limestone in the road cutting just
before Vanrhynsdorp. The TMG forms one last spectacular flat-topped mountain
looming over Vanrhynsdorp, the Matzikammaberg (see Figure 1 at top of
article), before retreating to
the right horizon as the northerly extension of the Great Escarpment.
Figure 2. Whaleback Mountains and Granite Koppies
Copper Mineralisation and Mining
Before
doing a quick geo-tour of the area some background on the copper mineralisation
and mining, which may be old-hat to many. The copper mineralisation is hosted
in noritoid rocks of the Koperberg Suite (c.1 160 Ma) which have been
intruded into the granites and gneisses in irregular lenses. These intrusions
are often associated with so-called ‘steep structures’ where the fabric of the
granite-gneiss steepens on both sides, becoming near-vertical in the centre (Figure
4). There are about 1 700 of these intrusives in the area. A piece of
the mineralised norite is shown in Figure 5 with chalcopyrite in patches
and veins. The oxidised parts of the ore bodies are characterised by green and
blue films and patches of copper oxides, as seen extensively at the Blue Mine
and van der Stel shafts (Figure 6). Approximately 2 million tonnes of
copper worth about R130 billion in today’s money were mined from about 32
concession areas in the period 1852–2004. This was the first commercial mining
to take place in South Africa and as with many mining areas, included boom and
bust periods.
Figure 4. Steep structure
Figure 5. Noritoid with chalcopyrite
Figure 6. Noritoid with copperoxides
Okiep area
First stop after a hassle-free trip from Cape Town was the historic mining area of Okiep. The O’oKiep Mine, as it was originally called, was started in the 1860s and for a time was the world’s richest copper mine. Apart from dumps and slag heaps, some interesting relics of this mining operation include a Cornish pump-house and smelter stack (Figures 7 and 8), both now national monuments. The pump installation was necessitated by the interception of large quantities of groundwater below about 116 m but the remaining pump/pump-house was installed when the mine reached 208 m and the existing pump couldn’t cope with the quantity of water. Why Cornish you may well ask?
Figure 7. Cornish Pump House
Figure 8. Chimney Stack
Well,
Cornish miners were called in to assist with mining operations and their legacy
can be seen in some local mine names such as ‘Wheal’, the Cornish word for a
mine. The pump-house has been disfigured visually somewhat by the erection of
an unsightly concrete fence if you compare my photograph (Figure 7) to
that in Cairncross and Dixon (1995, p121). There is a smaller smelter chimney
just off the road separating Springbok North from the main town area (see Figure
9 below).
Figure 9
Orbicular Diorite
Next
stop on my list was the orbicular diorite occurrence at Concordia. Orbicular
granite or diorite is a rare rock type found in only a few places in the world
and only two in South Africa (I can’t find any reference to the second
occurrence – does anyone know where this is?) I first heard of orbicular
granite as a student and tried unsuccessfully to find an occurrence in southern
Finland in 1973 and had a nice piece from Mount Magnet, Australia until
recently. I thought the site near Okiep was just off the N7 but found that it
was quite a bit further than this. I turned off the N7 at the Okiep sign and
expected to see some directions but it was only after about 10 km on tar to
Concordia that I found a sign to the site and turned onto a gravel road that soon
meandered out of habitation and then another sign showing “Orbicule ↑” as shown
in Figure 10. I followed this track for another 2 km or so and was
wondering where I was when I saw some parking areas marked out with whitewashed
stones but no other signage. This is a proclaimed national monument so I
expected a bit more guidance. Anyway, there was a guy digging amongst the rocks
nearby and he directed me to the koppie (Figure 11). The site is a bit
underwhelming but you can see the texture quite well on the exposed rock faces (Figure 12)
and can scramble around and take a lump if you want, which I did.
Figure 10. Orbicule Hill directions
Figure 10. Orbicule Hill directions
Figure 12. Orbicular diorite
Figure 13. Carolusberg Mine slimes dam
Carolusberg Mine
I didn’t visit the
old mine site itself but you can see the slimes dam from the main road through
the Goegap Nature Reserve (Figure 13), and it is a bit incongruous to
see such a large, or any, slimes dam within a nature reserve but I guess the
former came first. This mine exploited the largest complex of copper-bearing
noritoid intrusives, near the original Van der Stel shaft.
Figure 14
Blue Mine
Van der Stel Shaft
This national monument marks where Commander Simon van der Stel and his expedition sank some shafts into malachite-stained norite in 1685. A steep walk up the path on the side of the aptly-named Koperberg from the parking area takes you past some piles of norite with green, presumably malachite, stains, patches and films. A shaft just before the main one (framed by rectangular fencing in Figure 15) shows an example of the so-called ‘steep structures’ that characterise the noritoid occurrences of the Koperberg Suite (Figure 4). The main Van der Stel shaft and date plaque are shown in Figures 15 and 16.
Figure 15. Van der Stel Shaft
Figure 16. van der Stel Shaft Date Plaque
Figure 17. August Flowers
References
Viljoen, MJ. and Reimold, WU. (1999). An Introduction to South Africa’s Geological and Mining Heritage. Mintek. Randburg.
Norman, N. and Whitfield, G. (2006). Geological Journeys. Struik. Cape Town.
Cairncross, B. and Dixon, R. (1995). Minerals of South Africa. The Geological Society of South Africa. Johannesburg.
-Davenport, J. (2013). Digging Deep; A History of Mining in South Africa. Jonathan Ball. Jeppestown.
Further reading: Miller, D. 2010. Boom and bust: the copper mining towns of Namaqualand. South African Lapidary Magazine 42(3):34-39.
