Gold Mines In South Africa Research Articles

Determining hydraulic parameters of a karst aquifer using unique historical data from large-scale dewatering by deep level mining – a case study from South Africa

Although karst aquifers constitute some of the most important water resources worldwide, generally accepted methods for reliably characterising their hydraulic properties are still elusive. This paper aims at contributing to the discussion by a first-ever attempt to utilise various sets of unique historical data derived from draining a large dolomitic karst aquifer by deep-level gold mines in South Africa. In contrast to conventional pumping tests which only penetrate thick aquifers to a limited extent from surface, this draining took place at the very bottom of the aquifer offering the rare opportunity to capture its entire thickness of nearly a kilometre. The datasets have been treated as analogies to conventional pumping tests applying various types of analytical methods designed for porous media. In order to increase the robustness of the results and to account for specific local conditions a total of four different analytical methods were applied to calculate (horizontal) transmissivity and storage coefficients. The obtained values, in general, compare favourably to previous studies in the area and values reported in literature for similar aquifer types confirming earlier findings that Darcy-based methods can be successfully applied to karst aquifers if the scale of investigation is large enough. Apart from improving the understanding of local karst hydrology the present study also aimed at retrieving and preserving valuable and unique historical datasets that otherwise would have been lost for scientific evaluation and the proactive preparation for mine closure. Keywords : karst, dewatering, deep level mining, porous medium analytical methods, transmissivity, storage coefficient, Far West Rand

Uranium contamination of fluvial systems. Mechanisms and processes. Part II : dynamics of groundwater, stream interaction. A case study from Koekemoerspruit (South Africa)

Dissolved uranium from tailings-deposits of various goldmines in South Africa was found to migrate via seepage and groundwater into adjacent fluvial systems. The extent of the associated non-point pollution depends not only on the concentration of uranium in the water but also on the volumes of polluted groundwater seeping into the stream channel. While the uranium concentration in the groundwater is rather constant and therefore comparably easy to determine, the same is not true for the water exchange at the groundwater-stream interface. In order to track the relevant hydraulic processes, in-situ data-logger controlled probes were placed within the system measuring gauging heights and electric conductivity (EC) in 10-minute intervals. As a result of a steep hydraulic gradient between water-saturated tailing-deposits and the receiving watercourse, exfiltration (baseflow) of contaminated groundwater generally dominates. However, short-term inversions of the direction of flow (infiltration of stream water into the groundwater) were also observed. They are attributed the artificial flow-regime of the Koekemoer Spruit, which results from a pumping scheme that discharges dolomitic groundwater into the stream. Electricity costs-related differences of pumping rates lead to pronounced diurnal fluctuations of gauging heights in the stream, which in turn cause even higher fluctuations of the associated groundwater table (up to 90cm a day). The consequences and mechanisms of these man-made stream fluctuations for the hydraulic stream-groundwater interaction.

Mining, housing and welfare in South Africa and Zambia: an historical perspective

This contribution seeks to place the relationship between mining, housing and welfare in historical perspective in two Southern African countries with long histories of mining activity that continue to have large mining sectors, namely South Africa and Zambia. Mining capitalists and colonial, as well as apartheid, governments tended to resist urban permanence, but they were usually unable to stop it. Economists and social anthropologists, being less conscious than historians of the cyclical nature of mining, have been prone to discount the remarkable tenacity of the Zambian Copperbelt's urban residents in the face of mining downturns. By contrast, very little attention in the literature has been paid to the decline of gold mining in South Africa. In view of the Zambian precedent for urban resilience, it would be unwise to overlook the continuing influence of South African mining on urban settlement in spite of the industry's gradual decline over the last four decades. The patterns of development of new platinum mines in South Africa and new copper mines in Zambia show certain similarities and historical continuities, including a reluctance on the part of mining companies to accept responsibility for the housing and welfare of all their workers and their families.

Creating Safety Awareness through a Training Intervention: a Case at a Gold Mine in South Africa

In the productivity-driven mining industry, safety and employee engagement become a hazard. The mining industry in South Africa experiences challenges such as a high accident rate, employees who are not engaged and individual employees who do not see safety as their own responsibility because they think it is the responsibility of the safety department. A change intervention may create safety awareness among employees. There is a general lack of understanding among managers and academics regarding the effectiveness of such a programme. The main focus of the study being reported here was to determine the effectiveness of a mindset training programme to create safety awareness at a plant in the gold mining industry in South Africa. The empirical results showed that the concept of safety crystallised as a single factor in the after-training factor analysis whereas previously it was concealed in the interpersonal skills, safety and productivity-orientated factor.

Source Parameters of Picoseismicity Recorded at Mponeng Deep Gold Mine, South Africa: Implications for Scaling Relations

Abstract We investigate the source parameters of picoseismic and nanoseismic events ( M w >-4.1) recorded with a high-sensitivity seismic network at the Mponeng gold mine in South Africa to gain new insights into the scaling of small seismic events. The Japanese–German Underground Acoustic Emission Research in South Africa (JAGUARS) network, composed of one three-component (3C) accelerometer (sensitivity 50 Hz to 25 kHz) and 8 acoustic emission (AE) sensors, (sensitivity 1 kHz to 180 kHz) is located at a depth of 3268 m and covers the limited volume of approximately 300×300×300 m. The AE sensors are calibrated with respect to the 3C accelerometer in the frequency band 400 Hz–17 kHz. The waveform data of two datasets are analyzed; (1) the aftershock sequence of an M w 1.9 event that occurred approximately 30 m from our network, and (2) the postblasting activity recorded during working days, located at a distance >90 m from the network at the exploitation level. For the analysis we applied spectral fitting and spectral ratio methods. The calculated values of M w range from -0.8 down to -4.1 with corner frequencies 0.8 kHz–13.6 kHz (source sizes from 8 cm to 1.3 m). We observe static stress drops ranging from 1 MPa to 10.0 MPa with apparent stresses of 0.01 MPa–1.00 MPa. Stress drops are independent of the moment, suggesting self-similar behavior in the analyzed magnitude range -4.1 M w

SEISMICITY OF SOUTHERN AFRICA DURING 2006 WITH SPECIAL REFERENCE TO THE MW 7 MACHAZE EARTHQUAKE

Seismic activity recorded by the South African National Seismograph Network in southern Africa during the period January to December 2006 is summarized in this article. The South African National Seismograph Network was expanded to 23 seismological stations and the data communication infrastructure updated to transmit continuous waveform data in near real-time during 2006. Earthquake data, published in the Seismological Bulletins of the Council for Geoscience for 2006, was revisited and all tectonic earthquakes relocated together with mining related earthquakes that were located outside known mine boundaries. The resulting earthquake database comprises a total of 3875 located seismic events, the majority of which (79%) is located in the gold and platinum mines of South Africa. A total of 1460 events were ascribed to chemical explosions in opencast mines and quarries and flagged accordingly in the database. The recorded seismic activity, tectonic as well as mining-related, is discussed in terms of the error in location and the observed frequency-magnitude distribution. A fault plane solution for a M L =4.0 earthquake, located in the gold mines of South Africa, is also presented. The most significant earthquake occurred on the southernmost extension of the East African Rift System in south-western Mozambique and measured 7.0 on the moment magnitude scale. The earthquake was widely felt throughout the region, causing four fatalities, 27 injuries and damage to approximately 160 buildings.

Drug-Resistant TB Among Gold Miners in South Africa

Poor adherence to treatment protocols contributes to TB drug resistance. Prompted by a TB outbreak at a gold mine in South Africa in 2003, investigators assessed the evolution of drug resistance at this mine, which has a well-functioning TB-control program. Mine employees and their dependents (population, about 25,000 per year) were eligible for the study. Employees who had new lesions detected on biannual chest radiographic screening — and …

Statistical Properties of Mine Tremor Aftershocks

Mine tremors and their aftershocks pose a risk to mine workers in the deep gold mines of South Africa. The statistical properties of mine-tremor aftershocks were investigated as part of an endeavour to assess the hazard and manage the risk. Data from two gold mines in the Carletonville mining district were used in the analysis. Main shocks were aligned in space and time and the aftershock sequences stacked and analysed. The aftershocks were found to satisfy Gutenberg–Richter scaling, with a b value close to 1. Aftershock activity diminished with time in accordance with the modified Omori law, with p values close to 1. However, the relationship between the main shock and its biggest aftershock violated Baths law, with ΔM L ≈ 1.9 for main shocks with M L < 3 and increasing for main shocks with M L > 3. The aftershock density was found to fall-off with distance as r −1.3, suggesting triggering by dynamic stress.

Project CARE: Placer Dome’s Efforts to Help Laid-off South African Miners Find Remunerative Work

This essay examines a special program developed by the international Canadian mining firm, Placer Dome, to help recently laid-off workers find remunerative work in southern Africa. Shortly after it bought a 50% interest in the Deep South gold mine in South Africa, the mine laid off nearly 2600 workers. The firm gave redundant miners token severance pay and offered them opportunity to participate in training and counseling services at the mine site. Overwhelmingly, the miners came from homes all over southern Africa at great distance from the mine to which homes they chose to return. In addition, many had become ill from the HIV virus. Placer Dome soon realized that something more was required, given the very high rates of unemployment in the region. After securing grants from USAID and CIDA, and working with NGOs representing both the unions and mining companies in South Africa, the firm developed Project CARE. The project contacted workers where they lived and offered them or another proxy member of their households a variety of training, coaching, and consultative services. Within 2 years 65% of those contacted had either found new employment or started their own business. The project helped those households with HIV-affected ex-miners care for their affected family members. While describing the case, the essay raises more general ethical questions about the responsibilities of mining firms in particular for their redundant workers.

Observation of numerous aftershocks of an Mw 1.9 earthquake with an AE network installed in a deep gold mine in South Africa

Abstract This is the first report from the JAGUARS (JApanese-German Underground Acoustic Emission Research in South Africa) project, the overall aim of which is to observe ultra-small fracturing in a more or less natural environment. We installed a local (∼40-m span) network of eight acoustic emission (AE) sensors, which have the capability to observe up to 200 kHz at a depth of 3.3 km in a South African gold mine. Our specific objective was to monitor a 30-m thick dyke that remains as a dip pillar against active mining ∼90 m above our network. An M w 1.9 earthquake whose hypocenter was ∼30 m above the network occurred in the dyke. Although the mineowned geophone (4.5 Hz) network detected only five earthquakes in the surrounding 200×200×150-m3 volume within the first 150 h following the main shock, our AE network detected more than 20,000 earthquakes in the same period. More than 13,000 of these formed a distinct planar cluster (∼100×80 m2) on which the main shock hypocenter lay, suggesting that this cluster delineates the main shock rupture plane. Most of the aftershocks were presumably very small, probably as low as M ∼ −4. The aftershock cluster dipped ∼60°. This is consistent with normal faulting under a nearly vertical compression field, as indicated by nearly horizontal breakouts found in a borehole crossing the rupture plane.

Source Mechanisms of Mine-Related Seismicity, Savuka Mine, South Africa

We report full moment tensor solutions for 76 mine tremors with moment magnitudes (Mw) between 0.5 and 2.6 recorded by a network of 20 high-frequency geophones in a deep gold mine in South Africa. Source mechanisms convey important information on how in-mine stresses are relaxed, and understanding the nature of such mechanisms is essential for improving our assessment of rock mass response to mining. Our approach has consisted of minimizing the L2 norm of the difference between observed and predicted P, SV, and SH spectral amplitudes, with visually assigned polarities, to constrain all six independent components of the seismic moment tensor. Our results reveal the largest principal stresses in the mine are com- pressive, oriented near vertically, and relaxed through a mix of volumetric closure and normal faulting, consistent with a gravity-driven closure of the mined-out areas. Pre- vious moment tensor studies in deep mines had suggested that the distribution of seis- mic sources in terms of the volumetric-shear mix was bimodal. A bimodal distribution is compatible with our moment tensor solutions only for moment magnitudes above 2.2. Events in the 0:5 <Mw <2:2 moment magnitude range display a continuous distribution of their volumetric-shear mix. Online Material: Focal parameters for mine tremors at Savuka.

Extensively Drug-Resistant Tuberculosis, Lesotho

Extensively Drug-Resistant Tuberculosis, Lesotho

Source mechanism of mining induced seismic events — Resolution of double couple and non double couple models

Traditional assumption about a seismic source as a double couple (DC) can represent a serious limitation for describing mechanisms of mining induced seismic events. In mining conditions more general process than a shear slip can occur due to stress concentration on mined-out areas. We assume both non-DC components within the dipole description of the source — the moment tensor, and a single force. We processed five seismic events recorded at Driefontein gold mine in South Africa to demonstrate that waveform modeling is not successful enough due to poor information about the medium. Inversion of amplitudes of direct P- and S-waves is more prospective due to their smaller sensitivity to detail of the medium and possibility to correct them for ray bending and shear wave splitting prior to the inversion. Moreover, we are able to estimate the error of the resulting mechanism due to neglect of ray bending. All five events processed display non-DC mechanisms which are significant at 95% considering the mismodelling of the rock mass by a homogeneous isotropic medium. The source mechanisms are in agreement with the underground mining and geological structures. One event has a sub-vertical pressure single dipole complemented by an implosion, which is the body force equivalent of a collapsing horizontal crack or a burst of a pillar supporting the hangingwall of a mined-out area. Two events have mechanisms close to a pressure single couple. All three events are located on pillars. Two out of these three events can be assigned with a downward single force as an alternative mechanism, which matches the amplitude data successfully. It is the force equivalent of a mined-out area collapse, when a rock mass falls from the hangingwall to the footwall. The events are however rather strong, which would require too large rock mass fallen. One of the remaining events is a nearly horizontal tensile single couple, corresponding to a vertical tensional fault. It could be originated by a break of the hangingwall of a mined-out area, however the hypocenter of this event is deep into the footwall were there is no mining taking place. The last event is mostly DC accompanied by a compensated compressive dipole, which may be associated to nearly vertical dip–slip along a fault in the hangingwall. This event is located on the margin of a wide pillar which supports the interpretation.

Mineralogical, Chemical and Biological Characterization of an Anaerobic Biofilm Collected from a Borehole in a Deep Gold Mine in South Africa

A biofilm sample was collected from an anaerobic water and gas-flowing borehole, 1.474 km below land surface in the Evander Au mine, Republic of South Africa. The biofilm was 27 wt% ZnS, which was ∼ 2 × 107times more concentrated than the dissolved Zn measured in the borehole water. X-Ray diffraction indicated that the Zn was present in the form of fine grained, 4.7 ± 0.9 nm particles with smaller amounts of pyrite (FeS 2 ). Scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy confirmed the identity of these minerals in the biofilm. Using transmission electron microscopy, the fine-grained ZnS minerals were found to coat the 1 μ m-diameter rod-shaped bacteria that made up the primary substructure of the biofilm. The FeS 2 was present as framboids (spherical aggregates of 0.5–1 μ m FeS 2 crystals) up to 10 μ m in diameter and as large, 2–3 μ m euhedral crystals that were not nucleated on the bacterial surfaces, but were found within the biofilm. Analyses of 16S rDNA utilizing clone libraries and a phylochip indicates that the ZnS rich biofilm is dominated by methanogens with a significant sulfate-reducing bacterial population and minor sulfide and CH 4 -oxidizing chemolithotrophs. This biofilm community is sustained by sulfate, bicarbonate and H 2 -bearing paleometeoric water.

Investigating turnover intentions by role overload, job satisfaction and social support moderation

Gold mining in South Africa has played a significant role in the economic development of the country. However, the current economic, personnel and rationalisation pressures could imply a loss of production in this industry. The focus of this research fell on investigating the role that social support may play in the translation of employees’ role overload and job satisfaction on their intentions to leave the organisation. A cross-sectional survey design with a random sample was used (n = 206). Results indicate that job satisfaction is the most significant predictor of turnover intention, but that collegial support plays an important role in moderating the effects of role overload on turnover intention.

Seismic Moment Tensor Resolution on a Local Scale: Simulated Rockburst and Mine-induced Seismic Events in the Kopanang Gold Mine, South Africa

Seismic records contain information about the effect of the source as well as the effect of wave propagation through the rock mass. The effect of wave propagation is usually not well known as only simplified models of geological structures are available. Therefore, the information about the source retrieved by inverting seismograms may include errors due to incomplete knowledge of the rock mass along the propagation path, which in turn cause a distortion in the calculated moment tensor (MT). The distortion of the MT on a local scale was observed by inverting records of a simulated rockburst conducted at the Kopanang gold mine in South Africa. A dominant isotropic component of the explosive characteristics was found from the inversion. The deviatoric components retrieved from the blast are spurious. A test of their stability indicated that they are not significant, assuming an uncertainty above 5% for velocities and 10% for attenuation within the homogeneous model available for the mine. Thus, the retrieval of the MT from records of local networks in mines using a homogeneous model of the rock mass seems to be feasible. However, the homogeneous model of the rock mass can only be applied to close stations, within a few kilometers of the source. The seismic records from distant stations were too complex to be modelled by a homogeneous rock mass. Records of six mine-induced seismic events recorded at the Kopanang gold mine were also inverted. A vertical linear dipole along the pressure (P) axis was found for three of the events, suggesting a pillar burst. The mechanism of two events contains an isotropic implosion together with a nearly vertical dip-slip, and seems to indicate a combination of a cavity collapse with a down dip-slip along a nearly vertical fault. One event corresponds to a dipole along the tensional (T) axis. However, it is vertical, thus its association with tensile faulting of the hangingwall is uncertain.

Small slow‐strain steps and their forerunners observed in gold mine in South Africa

The Research Group for Semi‐controlled Earthquake‐generation Experiments in South African deep gold mines (SeeSA) has continuously monitored strain changes with a resolution of 24 bit 25 Hz at the Bambanani mine near Welkom. An Ishii borehole strainmeter was installed at a depth of 2.4 km near the potential M ∼ 3 earthquake source area. Instantaneous strain steps of ∼10−4 strains associated with two M2 events were observed within a length of seismic fault. These steps were followed by significant post‐seismic creep‐like drift, but not preceded by forerunners. Analysis of the continuous 25 Hz data reveals many smaller steps with much longer durations (100 ms ∼ 100 s) than seen in normal earthquakes (−1 &lt; M &lt; 2) with source durations of 1 ms∼50 ms. Some of the especially slow steps were preceded by accelerations in strain, the maximum being as large as one‐third of the step.

Review article: Analysing the crack coalescence in brittle rock materials

The understanding of fracture has tended to follow great public disasters (e.g. over 200 US ships suffered due to catastrophic failure during WW II, later several jet air-craft damaged, destroying some bridges and buildings, etc). Rock fracture mechanics dates back to early 60-s and its application to rock blast problems, collapses deep gold mines in South Africa, earthquake disasters, etc. Pure shear mode (Mode I) or mixed tension and shear mode (Mode I and II) fracturing are the most important in rock mechanics and geophysics. The goal of this paper is to summarize the existing fracture criteria and the observed crack growth firstly from single flaws, secondly from multiply (two) flaws. Analysing the fracture propagations different types of coalescence can be determined and classified. Using these modelling and analysing the observed patterns, for example we could forecast the new failures after the earthquakes or calculating the stability of rock slopes, etc.

Isolation and characterization of a Geobacillus thermoleovorans strain from an ultra-deep South African gold mine

A thermophilic facultative bacterial isolate was recovered from 3.2 km depth in a gold mine in South Africa. This isolate, designated GE-7, was cultivated from pH 8.0, 50 °C water from a dripping fracture near the top of an exploration tunnel. GE-7 grows optimally at 65 °C and pH 6.5 on a wide range of carbon substrates including cellobiose, hydrocarbons and lactate. In addition to O 2, GE-7 also utilizes nitrate as an electron acceptor. GE-7 is a long rod-shaped bacterium (4–6 μm long×0.5 μm wide) with terminal endospores and flagella. Phylogenetic analysis of GE-7 16S rDNA sequence revealed high sequence similarity with G. thermoleovorans DSM 5366 T (99.6%), however, certain phenotypic characteristics of GE-7 were distinct from this and other previously described strains of G. thermoleovorans.

The Silent Scourge? Silicosis, Respiratory Disease and Gold-Mining in South Africa

Mining companies in South Africa have publicised their benevolent concern for the health of their workers. However, there are legal, practical and political reasons for this concern. This article is concerned with the historical roots and complex interactions between tuberculosis, respiratory disease and HIV/AIDS. While the incidence of such illnesses remains high or growing, the post-apartheid order may compel the mining houses to take their responsibilities for the long-term health of their workforces more seriously.