VOLUME 53 . JUNE 2018

INSIDE:Handover of groundwater boreholes to the Beaufort West Municipality I 1Mahlako Mathabatha

Ingress control activities in the East Rand goldfield of the Witwatersrand Basin I 3Kefyalew Tegegn

The Superior Golden Loop I 5Taufeeq Dhansay

Geoscientists receive doctorates I 7Nontobeko Scheppers

Field transportation of geologists from the early 1900s up to 1930 I 7Rehan Opperman

Handover of groundwater boreholes to the Beaufort West Municipality

Two boreholes with good-quality groundwater were handed over to the Beaufort West Municipality.

The Council for Geoscience and the Department of Mineral Resources hosted a ceremony in Beaufort West on Tuesday, 13 February 2018 to hand over two high-yielding groundwater boreholes to the Beaufort West Municipality. The handover was initiated after the announcement by the former Minister of Mineral Resources, Mr Mosebenzi Zwane at the official opening of the Mining Indaba on 5 February 2018 where he alluded to the good-quality groundwater that had been discovered by the Council for Geoscience in the Western Cape Province, particularly in the Beaufort West area. Pump tests on the two high-yielding boreholes indicated a combined monthly supply of about 33 million litres of water, which will sustainably cater for approximately 44 938 people. Laboratory tests indicated that the water is of good quality suitable for domestic and agricultural

purposes. With these quantities, this intervention by the Council for Geoscience and the Department of Mineral Resources will significantly contribute towards alleviating the water crisis plaguing the Beaufort West area.

A Memorandum of Understanding was signed by representatives of the Department of Mineral Resources/Council for Geoscience and the Beaufort West Municipality, followed by an official handover of the boreholes by the Director-General of the Department of Mineral Resources, Advocate Thabo Mokoena, to the Mayor of the Beaufort West Municipality, Councillor Jeffrey van der Linde alongside the Chairperson of the CGS Board, Dr Humphrey Mathe and the Chief Executive Officer, Mr Mosa Mabuza. These boreholes were drilled during a five-year geoenvironmental baseline study in the Karoo area in

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For more information contact:Mahlako MathabathaMarketing and Communication+27 (0)12 841 1220mmathabatha@geoscience.org.za

South Africa that is currently in progress. The main purpose of this study is to identify possible environmental impacts from anticipated shale gas exploration and exploitation. As part of groundwater research and monitoring, the Council for Geoscience drilled five boreholes to a maximum depth of 169 m in the Beaufort West area. According to Minister Zwane, this is a result of the multidisciplinary and integrated approach to geoscience mapping in the country, which is

yielding scientific results in response to societal issues.

Councillor Jeffrey van der Linde conveyed his gratitude to the Council for Geoscience for bringing water to the Beaufort West community during the period of drought. Dr Mathe thanked the Beaufort West Municipality for their support and commitment during the period of exploration and urged the community to continue their support

of the Council for Geoscience in its research of the Beaufort West area. He furthermore applauded the team behind this project for their excellent work.

GeoClips I 3Geoclips - Volume 53 - June 2018

Ingress control activities in the East Rand goldfield of the Witwatersrand BasinBackground

The ingress of surface water into underground mine workings has been identified as a significant hazard in the goldfields of the Witwatersrand. The cessation of operations at the gold mines of the Witwatersrand has led to the flooding of underground workings that may result in uncontrolled discharge of acid water from the underground workings to the surface, if not properly managed. As a result, pump stations and associated treatment plants have been developed to alleviate this problem. However, these solutions are costly to operate and, therefore, reducing the volume of ingress will reduce the long-term operating costs of these plants.

The Council for Geoscience initiated a study in 2002 to identify the ingress points into the Witwatersrand goldfields. To date, this study has attempted to quantify the amount of ingress for each point by applying different methods to measure direct inflow and outflow.

One of the main activities of the 2016/17 financial year in the ingress control task entailed assessing, checking and monitoring the current condition of previously identified ingress points. The task focussed mainly on the East Rand goldfield in view of updating or modifying recommendations that had been made by previous studies. However, given the probability that the surface conditions of the identified ingress points may have changed since these studies were carried out (owing to natural processes and anthropogenic activities such as the reworking of the mine dumps), it was deemed necessary to verify the existing ground conditions at these sites once more.

Identification of the Modderbee crack as an ingress point

A new ingress point was identified south of Modder Road at the geographical coordinates of latitude 26.17530°S and longitude 28.38437°E. The crack is 25 m long, 5 m wide at the surface and

about 1.5 m deep and plunges to the west where the ingress point is situated at the margin.

The Modderbee crack ingress has been monitored on an annual basis to cover at least one hydrological cycle. On 4 April 2016, a small volume of water was observed to be entering the crack. On 20 May 2016, using the bucket and stopwatch method, the flow of water was measured at 6 L/s. On 5 August 2016,

the Modderbee ingress area was dry and there was no flow of water into the crack. By 13 February 2017, the surface opening had been filled to the level of the surrounding wetland, suggesting that the rate of downward water flow is not sufficient to drain the water flowing into the crack.

Possible methods to stop the ingress of water into this crack were proposed and a working sketch was prepared.

Surface conditions and monitoring of the surface conditions and ingress in the Modderbee crack.

Proposed design for sealing the Modderbee crack.

A B

C D

Sealing of Modderbee crack

5 m

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Sealing of the Modderbee crack (construction)

The road excavation indicated that the overburden soil, with a thickness of more than 80 cm, consists of remnants of slimes material left over from the removal of historical mine dumps. This material was cleared beyond the perimeter of the planned 12 m crack sealing surface. The first level of excavation to a width of 12 m around the crack continued to a depth of 0.40 m within the same slimes material. For the second level of excavation, the width was reduced to about 3.20 m, still keeping the crack at the centre, while excavation continued using manual labour to cover the next 0.50 m.

The third level of excavation was reduced to a width of 1.2 m around the crack, gradually reduced to 0.10 m up to the base of the crack. The first part of this bottom excavation was within the contact layer of the top soil and the underlying weathered quartzite that gradually hardens becoming very difficult to excavate manually. Finally, the crack, situated on hard quartzite rock continuing down to an unknown depth (at this stage), was prepared for sealing.

At this point, the field team identified an underground channel when they heard the sound of water flowing through the crack. Geophysical tests were conducted with additional investigation methods being recommended to investigate the depth of the crack and the possible underground channel. It is proposed that four percussion boreholes be drilled to a maximum depth of 50 m when site conditions allow the team to access the site with the drilling machine.

Upon completion of the excavation work, sealing of the crack started from the bottom up to ground level by plugging the crack with cobbles and gravels. A 1.2 m x 0.6 m deep formwork was prepared over the entire length of the crack.

Concrete of 25 Mpa was poured into the formwork and compacted to reduce voids. The top of the concrete was covered by a well-compacted silty clay soil up to a level of 0.4 m to reach the ground surface. A bottom geomembrane

Base of the crack exposed and ready for sealing.

(bidm 6) was placed below the HDPE impermeable plastic followed by the top geomembrane (bidm 6) to cover the entire prepared surface over a width of 12 m and a total length of 25 m, including the area beyond the crack.

For more information contact:Kefyalew Tegegn Engineering Geoscience and Geohazards+27 (0)12 841 1508ktegegn@geoscience.org.za

The top 0.25 m of the excavated ground above the impermeable membrane was also covered by compacted sandy silty clay. The final step for sealing the crack was to rehabilitate the site and to fix a hazard warning post.

A. Concrete filling.

B. Completed concrete work.

C. Protective membrane (bidm 6).

D. Impermeable membrane (HDPE).

E. Upper protective membrane (bidm 6).

F. Completed ground.

A B C

D E F

GeoClips I 5Geoclips - Volume 53 - June 2018

Overview

The Council for Geoscience and the Geological Survey of Canada have an ongoing Memorandum of Understanding and Implementing Agreement. This agreement aims to promote the exchange of institutional knowledge and to explore possible areas of collaborative research between the two organisations. Collaboration officially began in October 2016 when the Council for Geoscience hosted several scientists from the Geological Survey of Canada for a workshop and field trip. The workshop covered various aspects of mineralising systems research being undertaken by the respective organisations and was followed by a geological field trip and tour of several mines in the Limpopo and Mpumalanga Provinces. (For more information refer to Geoclips Volume 47 of December 2016.)

The reciprocal part of this bilateral agreement occurred in October 2017 when the Geological Survey of Canada hosted several scientists from the Council for Geoscience. Similarly, this trip began with a workshop discussing various areas of research and a tour of the central office of the Geological Survey of Canada in Ottawa, Ontario. The tour included a visit to the laboratories of the survey to view the ID-TIMS (isotope dilution thermal ionisation mass spectrometer), SHRIMP (sensitive high-resolution ionisation microprobe) and simultaneous multi-collector and quadrupole LA-ICPMS (laser ablation inductively coupled plasma mass spectrometer). These instruments enable an exstensive range of analytical measurements and ultra-high-resolution geochronological investigations.

The workshop was followed by a field trip to some of the most famous geological and mineralised exposures of Canada. Several notable similarities to South Africa’s own geology were apparent and discussions ensued on the various types of research being undertaken on these geological terrains. The team visited deposits of the St Lawrence Platform, which is similar in age to the Cape Basin, crossed the Grenville Province, which has a similar tectonic setting and age to the Namaqua-Natal Belt, and eventually

The Superior Golden Loop

Geological map of Canada simplified according to lithological ages. The insert shows a map of the field trip

with stars indicating various locations of interest.

entered the Superior Province, which has several similarities to Archaean rocks of the Kaapvaal Craton. The team also paid a brief visit to the Appalachian Orogen, which has a similar tectonic setting and age to the Saldanian Belt.

Superior Province

The ca 2750–2687 Ma Abitibi Greenstone Belt was the main focus area of the field trip across the Superior Province. The Abitibi may be subdivided into several sections based on its characteristic geochemical and geochronological signatures. The rocks of the Abitibi consist of a lowermost succession of ultramafic to mafic volcanic rocks often interlayered with felsic volcanoclastic rocks. There is a gradual increase in the occurrence of sedimentary derived siliciclastic rocks in the overlying sequences, which are often capped by a thick layer of conglomerate.

The Abitibi is surrounded and intruded by several plutonic bodies and intersected by an array of faults that run parallel to the overall trend of the greenstone belt. Geochemical differences across major fault structures suggest that some of these probably represent ancient tectonic boundaries signifying accretionary processes. The structures also provided conduits for the transport and concentration

of hydrothermal fluids that are typically rich in remobilised precious metals such as gold, silver, copper, lead and zinc. Several of these mineralised systems were visited throughout the Abitibi.

The field trip included a visit to the Sudbury region. This area is particularly noteworthy for the Sudbury Igneous Layered Intrusion, which hosts significant nickel deposits. The emplacement of this large igneous complex is linked to a ca 1850 Ma extraterrestrial impact that formed an approximately 200 km wide basin. After formation, this basin was rapidly filled by an impact-related melt sheet. The large volume of the melt sheet provided a significant heat source enabling the development of a hydrothermal system and the remobilisation and concentration of nickel-rich melt. The extent of this impact event can be traced for several hundred kilometres and is apparent with evidence of pseudotachylite melt segregation and brecciation, and the widespread development of shatter cones.

Grenville Province

The regions surrounding the Superior Province are defined by several high-grade orogenic zones. One of the most prominent orogenic zones crossed during the field trip was the Grenville Province. This province forms a high-grade orogenic belt along

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A B C D

E F

A B C D

For more information contact:Taufeeq DhansayMapping Geoscience+27 (0)12 841 1075tdhansay@geoscience.org.za

the southwest boundary of the Superior Province, which formed during the mid–late Proterozoic amalgamation of Rodinia and comprised several fragments of older Archaean volcanosedimentary rocks. The tectonometamorphic history of the Grenville highlights several periods of deformation linked to progressive accretion. This began as early as ca 1710–1600 Ma, with peak metamorphism at ca 1080–980 Ma. Postcollisional magmatism from ca 985–955 Ma marked the end of accretion and the beginning of Rodinia breakup. The postcollisional magmatism also includes several phases of extensively mined

Stromatolite (A) and carbonate with brachiopod (B) of the St Lawrence Platform and migmatitic paragneiss of the Grenville Province (C and D).

peraluminous and rare earth element bearing plutonic rocks.

St Lawrence Platform

Overlying the southern extent of the Grenville Province and extending up to, and also overlying, the foreland of the Appalachian Mountains, is the St Lawrence Platform. The field trip briefly explored the St Lawrence units around Ottawa, Quebec City and on the flanks of the Grenville Province. These mostly comprise Cambrian to late Ordovician carbonate and siliciclastic units, which also include

highly organic-rich sequences notable for petroleum and natural gas resources.

Future work

The workshop and field trip in Canada concluded the first phase of the bilateral agreement between the Council for Geoscience and the Geological Survey of Canada. Several themes were discussed, including the development and management of an accessible and dynamic geodatabase and the importance and applicability of an extensive analytical isotope laboratory. In addition, several potential areas of joint research were defined with the aim of gaining a better understanding of the evolution and mineralising systems operational during the Archaean. Both institutions will now work towards realising the various defined themes in view of initiating applicable joint research projects.

Various lithologies around the Superior Province: A. Sudbury impact breccia with pseudotachylite and overprinted by later glacial striations; B. Impact shatter cones; C. Timiskaming conglomerate; D. Porcupine turbidite; E. Tisdale sheared pillow lavas; F. Kid Munro komatiite with a spinifex texture.

GeoClips I 7Geoclips - Volume 53 - June 2018

Geoscientists receive doctorates The Council for Geoscience wishes to congratulate two of its staff members, Nigel Hicks and Taufeeq Dhansay, whose hard work has paid off, earning each of them a doctoral degree.

The seismic stratigraphy, geological evolution and CO2 storage potential of the offshore Durban Basin, South Africa.

Dr Hicks undertook a basin-scale assessment of the Mesozoic basin fill within the offshore Durban Basin on the east coast of South Africa. Carbon capture and storage (CCS) is a short- to medium-term climate change strategy designed to reduce CO2 emissions from large-scale emitters. South Africa, like many countries worldwide, is heavily reliant on fossil fuels for energy supply and is a significant contributor (in terms of per capita emissions) to CO2 emissions on a worldwide scale. Storage of anthropogenic (man-made) CO2 is a key mitigation technique for the reduction of global emissions. Successful storage of CO2 has been undertaken internationally in a number of geological mediums such as depleted oil or gas reservoirs, unmineable coal beds, deep saline water saturated aquifers and basaltic formations, in onshore and offshore environments. Dr Hicks’s PhD project

entailed a basin-scale (10 000 km2) evaluation of the geology and structure of the offshore Durban Basin in order to identify, categorise and rank potential storage media that may have the capacity to store carbon dioxide.

On the evolution and mechanics of the brittle upper crust below South Africa: Implications towards the sustainable

Dr Nigel Hicks received his PhD degree from the

University of KwaZulu-Natal.

Dr Taufeeq Dhansay (left) at the graduation ceremony

of the Nelson Mandela University in Port Elizabeth.

transformation of exploration/exploitation in the Earth’s Critical Zone

Dr Dhansay investigated how brittle features in the upper crust control important Earth system processes such as the concentration of energy and natural resources (i.e. geothermal, gold and natural gas) and how dynamic kinematic modelling can be used to manipulate these brittle features for sustainable exploration/exploitation.

For more information contact:Nontobeko ScheppersHuman Resources+27 (0)12 841 1201nscheppers@geoscience.org.za

Field transportation of geologists from the early 1900s up to 1930Browsing through some old photographs in the archives of the Council for Geoscience in Pretoria provides one with insight in what the geologists of yesteryear had to endure during their travels to do fieldwork.

In the early 1900s, the wagon was the main means of transport (photograph A). Travel times were long and fieldwork trips often extended for up to six months or more. Roads and shops were sparse in large parts of rural South Africa and geologists often had to be self-sufficient for long periods in between visits to shops. Water supplies for human and animal consumption were obtained from streams or fountains. During the early 1900s, geological mapping in the former Transvaal mainly focussed on the Bushveld Complex and the Lowveld areas. The wagons were mostly drawn by

donkeys rather than horses. In the Lowveld, this was likely due to the presence of the tsetse fly, with donkeys believed to be less susceptible to diseases caused by the tsetse fly than horses.

Wagons were mostly used to haul supplies with a smaller spider or buggy wagon being used for general travel and leisure. On some photographs it would seem that wagons were sometimes used for accommodation and as kitchens as well.

In photograph B, camp was set up near what could have been a shop with a buggy carriage in the near distance. For interest’s sake, what appears to be a double-barrelled shotgun (see insert) is visible to the left of the woman in the photograph. The shotguns were probably

used for killing snakes in and around the camp, hunting small game for fresh meat and to protect the donkeys from animals of prey at night — a real threat in the early years of geological mapping!

The smaller buggy or spider carriages were often used for activities of leisure as can be seen in the photograph of people standing in front of a baobab tree near Leydsdorp (photograph C). An almost exact photo, but with a person standing next to the baobab for scale, appears in Memoir 6 (1912) of the then Geological Survey.

By the early 1920s, motorcars seemed to have been fully adopted by the Geological Survey. However, roads were often non-existent and wagon tracks were used as roads in rural areas. Photograph D was

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Private Bag X112, Pretoria 0001, South Africa / 280 Pretoria Street, Silverton, Pretoria 0184, South AfricaTel: +27 (0)12 841 1911 / Fax: +27 (0)12 841 1221 / www.geoscience.org.za

taken on 30 January 1922 during the Shaler Memorial Expedition. The caption of the photo reads “Donkeys pulling motorcars over deep sands of the Gamka River”. It would seem donkeys were still ruling the roads in parts of South Africa. It must have been quite a mission showing South Africa to overseas visitors utilising dry riverbeds as roads! The dates in the photo album showed that the photos at Matjiesfontein and the Gamkaskloof were taken two days apart. It likely took most of the day to travel the approximately 120 km between the two locations.

By the late 1920s, travelling by motorcar seemed much easier and photos taken by the well-known Dr A.L. Hall showed motorcars traversing rivers far and wide via ponts at places such as the Olifants River Pont — Sekukuniland (photograph E), and the Komati River near Swaziland.

In photograph F, a person is shown riding a motorbike that had most likely been used as a means of private transportation by one of the Geological Survey geologists residing in Pretoria during a local field trip. The photo was taken from a locality approximately where the present-day Mayville in Pretoria is situated, facing northwards towards Wonderboompoort. It seems wicker-style sidecar bodies were very popular during the 1920s.

From here on the photographic record of motor vehicles used by the old Geological Survey is sketchy. Hopefully, more historical images will be found of the modes of transportation during fieldwork.

For more information contact:Rehan OppermanEconomic Geology and Geochemistry +27 (0)12 841 1121opperman@geoscience.org.za

A. Donkey-drawn wagon used for fieldwork. B. Wagon and buggy with double-barrelled shotgun shown in the

insert. C. Baobab tree near Leydsdorp. D. Donkeys pulling the motorcars over deep sands, Gamka River,

1922. E. Crossing the Olifants River in 1929. F. Motorbike with wicker-style sidecar.

A B

C

D

E F