GWD/IAH Groundwater Conference

22-24 September 2011

Gauteng, South Africa

The tour will leave from the CSIR Conference Centre in Pretoria on Thursday morning, 22 September. Now part of Tshwane Metropolitan Municipality, Pretoria is built on ancient shales and quartzites of the Pretoria Group which form a series of east-west trending ridges – the Conference Centre balcony has a nice view of these. A variety of less common rocks surround the area:

Pretoria, City of Tshwane

Simplified map of the geology of South Africa (courtesy of Council for Geoscience)(See page 9 for detailed Stratigraphic Classification of South Africa)

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Half an hour’s drive east is the century-old Premier diamond mine, where the world’s largest gem-quality diamond was found - the Cullinan Diamond. Cut and polished, this rough diamond gave rise to several magnificent jewels, including the legendary Great Star of Africa. Premier Mine is still one of the very few sources of blue diamonds. Swapping forms of carbon, the Mpumalanga coalfields a little further east yield the rivers of coal for the giant power stations that underpin South Africa’s economy.

The tour route

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To the south of Pretoria lie the gold-bearing Witwatersrand rocks, home to the earth’s greatest gold mines, where the City of Johannesburg rose from the veldt in a few decades of fevered speculation after the precious metal was discovered in 1886. Further south is the Vredefort Structure, the earth’s largest and oldest known meteorite impact crater. Pretoria’s northern boundaries touch the Bushveld Igneous Complex, a layered igneous intrusion the size of Ireland, where almost all the world’s platinum group metals are found. Huge mines strip these precious resources, working in tandem with giant refineries set amongst the area’s distinctive koppies and boulders. Much further west are big iron and manganese deposits: here, Sishen iron-ore mine, one of the world’s largest open-pit mines, produces millions of tonnes of high-grade ore every year. Just south of Pretoria’s city centre are outcrops of the stromatolitic, karstified Malmani Dolomites (Chuniespoort Group), amongst South Africa’s best aquifers. The copious springs known as Pretoria Fountains rise in these rocks - a major reason for Pretoria’s location, the springs are still an important part of the city’s water supply. Even more precious than the water are the fossils in these rocks - a part of the dolomites south-west of Pretoria is known as the Cradle of Humankind World Heritage Site, where it is estimated that a third of all African hominin fossils have been found. The famous Australopithecus fossils “Mrs Ples”

Map of the Bushveld Complex (courtesy of the Council for Geoscience)

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and “Little Foot” were found here, whilst in 2008 Prof. Lee Berger of the University of the Witwatersrand discovered a new human ancestor, the 1.9 Ma Australopithecus Sediba. The Au. Sediba bones are arguably the most complete early hominid skeletons ever found - fossils such as these have been described as amongst the earth’s most difficult-to-find objects! Interestingly, “Sediba” means spring or fountain in the Sotho language, bringing to mind the area’s copious groundwater resources that played a role in the preservation of the bones.

After leaving Pretoria the tour will head east on the N4 highway, the main transport link to Maputo in Mozambique, passing through Bronkhorstspruit to our first stop just outside of eMalahleni (formerly known as Witbank). This rapidly growing town is built on coal, with more than 22 collieries in its municipal area. eMalahleni also lies on the railway line linking Pretoria to Maputo in Mozambique. The coal resources of the area (Ecca Group of the Karoo Supergroup) and associated power stations and industries are a considerable source of prosperity, but have a downside in the underground fires, water pollution and occasional thick smog for which the area is known. Our first stop will be at an innovative plant treating polluted water. The plant is a public-private partnership between eMalahleni municipality and coal mining companies Anglo-Coal and BHP Billiton, and desalinates water (mainly groundwater) polluted by mining activities, making it available for public supply. The plant began operations in 2007 and has a design capacity of over 20 Ml/day. It has won environmental awards and is

often quoted as an example of the successful use of technology to turn an environmental liability into a valuable asset. We will spend about an hour at the plant, and hear a short talk by the plant operators. There will be an opportunity to ask questions.

The flatter, more subdued topography of the Karoo sedimentary rocks can be seen from the N4 highway as we travel further east after leaving eMalahleni. The stacks and cooling towers of giant coal-fired power stations dot the horizon,

including Arnot, Duvha, Hendrina and the 4116 MW Kendal station, one of the largest coal-fired power stations in the world. After stopping for lunch at the Star Stop just outside Machadodorp, we will turn off the N4 to travel through some scenic country down towards the town of Barberton.

The Australopithecus “Mrs Ples”

eMalahleni / Witbank

Eskom’s Kendal power station

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The tour route drops down from the Highveldt plateau, from the relatively young Karoo rocks through outcrops of hard Pretoria Group quartzites, down to the Lowveldt around Barberton, underlain by some of the oldest rocks still found on earth. Views from the escarpment are often spectacular, and the sheer cliffs formed by the quartzites are havens for eagles and vultures. Below the Pretoria Group are the dolomites of the Chuniespoort Group, which outcrop here too. (Some still speculate – against all evidence - that groundwater in these dolomites is in hydraulic continuity with those in Gauteng!) We will make at least one stop on the descent from the plateau to inspect the rocks, and admire the scenery. Average temperatures on the Lowveld are a fair bit higher than those of the Highveld, and the change is noticeable in the vegetation and animals in the area. Sub-tropical temperatures make the area suitable for avocado pears, bananas, coffee, mangoes and other agricultural products – visitors may see the occasional overloaded bakkie staggering up the pass towards Gauteng filled with goods for sale.

BarbertonWe will aim to arrive in Barberton by the late afternoon, and will travel to our accommodation, The Old Coach Road Guest House. Here we can relax with a beer, or perhaps take a short walk to admire the geology and unique plants. The 3.5 Ga Barberton Greenstone Belt (a sequence of mafic to ultramafic lavas and metasedimentary rocks) attracts scientists from around the world, who come to study this ancient remnant of the early earth’s crust, containing some of the oldest traces of life on earth.

Escarpment

Old Coach Road Guest House (from their website) Old Coach Road Guest House is tucked away in the Barberton Mountainlands Nature Reserve

9km outside Barberton on the R38, direction Kaapmuiden. The name is derived from the coach

road between Barberton and Delgoa Bay, used by transport riders delivering supplies to the many

gold prospectors during the gold rush days of 1874-1898. The route was also made famous by Percy

Fitzpatrick and his dog Jock. The remains of a portion of this road runs through the property. Kruger

National Park (Malelane Gate) is only 65 km from Old Coach Road and is easily accessible for a day

visit. We will provide you with a breakfast basket for an early start. We are fully licensed. Enjoy a late

afternoon drink in our bar or view the sunset from our sundeck. We often have unexpected guests!

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Structurally complex and often very beautiful, the rocks of the Barberton Mountain Land also happen to be gold-bearing – the precious metal was discovered here in the early 1880s (just before the bigger deposits on the Highveld) and for a while the area was the centre of a gold rush, complete with colourful characters propping up the bars in the now-deserted gold rush town of Eureka City. In its heyday this gold rush town had bars, a racecourse, hotels and a music hall. Barberton was also the home of Sir Percy Fitzpatrick, the author of Jock of the Bushveld, and some say the site of Africa’s first stock exchange.

The mining company Pan African Resources still mines gold in the area, operating three mines – Fairview, New Consort, and Sheba – which together produce more than 100 000 oz gold per year at a grade of around 10g/tonne. Sheba Mine is one of the world’s oldest and richest gold mines. Barberton Mines is also the site where the BIOX® (‘Biological Oxidation’) process was pioneered. This is a more environmentally friendly process of releasing gold from the sulphide ore, using microorganisms. Barberton is still used as an international training facility for all BIOX® plants. Gold is also recovered from old tailings deposits. Today impacts of mining on the environment, including groundwater, are controlled by law and Pan African Resources has a range of measures in place to meet these obligations.After breakfast on Friday morning, we will travel to the headquarters of Pan African Resources, for a discussion with the mine environmental manager Mr Clemens Kiessig and the chance to see some of the above-ground mine workings and facilities.

After leaving the mine at Barberton, the tour will travel north through Nelspruit past the famous Sudwala Caves along the bottom of the escarpment, following the outcrop of the Malmani dolomites. Although these are the same geological group as the major dolomite aquifers in Gauteng, they are geomorphologically distinct and are far less developed for their groundwater resources. Consequently less is known about the hydrogeology of the area. Groundwater levels are controlled by topographical variation and the location of surface drainages, and any impacts of over-abstraction are not discernable with current data. Water quality is generally

Dolomites

The bestseller “Jock of the Bushveld”

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Dolomites near Pilgrims Rest - old artisanal mine

workings

Pilgrims Rest areaOn Saturday morning we will start our trip back to Pretoria, travelling via the historic town of Pilgrim’s Rest. If time allows we will stop in this fascinating town for a stroll and a coffee. There is a long history of small-scale gold mining in this area, most notably around Pilgrim’s Rest and Sabie. Small tunnels and workings can be seen in many of the hillsides from the road, chasing quartz veins in the dolomites. These workings are today often a haven for bats and other small mammals.Although gold has probably been mined in the Pilgrim’s Rest area on a small scale since prehistoric times, it was the discovery of gold on a farm near Sabie in 1873 that sparked South Africa’s first gold rush. The early gold finds were mainly of alluvial gold, panned from streams in the area. Later, larger companies began to exploit gold-bearing ores in the surrounding dolomite rocks. In 1895 the Transvaal Gold Mining Estates (TGME) company was formed, and by the start of the First World War around 14 000 tons of ore a month were being processed, producing more than 112 000 ounces of gold per year. The average

Chestnut Country Lodge (from their website)Chestnut Country Lodge is situated in the beautiful Kiepersol district near Hazyview in Mpumalanga,

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good, although a small number of sites do show evidence of possible pollution. The potential yield of scientifically sited boreholes is not known, but may be considerable. The tour will stop in two or three places to examine the rocks, view old mine workings, and to stretch our legs. Lunch will be a picnic or snack along the way. We will stay the night at the luxurious Chestnut Country Lodge near the town of Hazyview, very close to the Kruger National Park.

grade is estimated at about 8g/ton. Gold is associated with quartz veins in the dolomite, which follow zones of weakness such as thrust fault planes. These veins were followed over considerable distances by early miners, utilising a range of techniques to extract the ore. By 1911 a hydroelectric power plant at Belvedere in the Blyde River Canyon was providing electricity to Pilgrim’s Rest and its ore reduction plant, making Pilgrim’s Rest the second town in South Africa after Kimberley to be electrified. The rusting steel electricity pylons that brought power to Pilgrims Rest are still standing, although no longer used.Whilst all mining operations were closed by the early 1970s, leaving behind abandoned shafts, adits, spoil heaps and other features, mining has today restarted at certain sites due to the buoyant gold price and new recovery technologies. There are currently a number of applications for new mining permits awaiting approval. Recovery of gold from old spoil heaps is also an economically viable activity at a small scale, and is planned or is taking place at several locations, mainly by the heap leach method. The scattered remnants of historical small-scale mining operations (e.g. adits and spoil heaps) are a source of small amounts of acid mine drainage (AMD), as groundwater percolates through the disturbed ground. This is likely to continue for many years, but is thought to have relatively local impacts on the groundwater regime with subsequent diluted impacts on receiving surface water bodies (e.g. Elands River). This is because the volumes are low compared with the amounts of groundwater, and the pollutants are also attenuated by riparian vegetation and the natural buffering potential of the aquifer.

Travelling back up the escarpment via a spectacular road pass, we will come to the town of Dullstroom. This is a small, upmarket holiday town and the centre of South Africa’s fly-fishing industry. Some have compared the local scenery to Scotland (perhaps after a whiskey or two!) We will stop in Dullstroom for lunch, and have the chance to try some of the town’s excellent artisanal beer produced by the local microbrewery. Smoked trout, trout pate and other fishy dishes are local specialties, and are well worth tasting.

Leaving Dullstroom at about 14:00, we will aim to be back in Pretoria by about 17:00.

Dullstroom

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Bourkes Luck potholes, near Pilgrims Rest

An abandoned tailings dam, near Pilgrims Rest

Further reading:

Council for Geoscience website: www.geoscience.org.za

Fitzpatrick P (1907) Jock of the Bushveld. Various publishers.

Johnson M.R., Anhaeusser C.R. and Thomas R.J. (2006). The Geology of South Africa. Jointly published by the Geological Society of South Africa, Johannesburg and Council for Geoscience, Pretoria.

McCarthy T and Rubidge B (2005) The Story of Earth and Life. A Southern African perspective on a 4.6 Billion Year Journey. Struik Publishers / Johnnic Publishing Group, Cape Town.

Norman N and Whitfield G (2006) Geological Journeys: A traveller’s guide to South Africa’s rocks and landforms. Struik Publishers and Council for Geoscience, Cape Town.

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Notes

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Technical Tour Leader: Jude CobbingSLR Consulting/IAH–SA National Secretariat

Tour Logistics Coordinator: Kerry Ririe Travel Consultant, Pembury Tours

Tel: +27 12 991 8881Fax: +27 12 9911907

After Hours: +27 83 612 0413Email: jude@watergc.co.za

Website: www.slrconsulting.com

Tel: +27 41 581 2581Fax: +27 41 581 2332

After Hours: +27 82 327 7505Email: kerry@pemburytours.comWebsite: www.pemburytours.com