Experimental measurements of seismic velocities on core samples and their dependence on mineralogy and stress; Witwatersrand Basin (South Africa)

Nkosi, Nomqhele Z.; Manzi, M.; Drennan, Gillian R.; Yılmaz, Halil

doi:10.1007/s11200-016-0804-x

Cited by 8 publications

(6 citation statements)

References 43 publications

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“…The target of the study is to map the Black Reef (BLR), as well as the relationship between the Government and Hospital Hill subgroups (West Rand Group), and between the Hospital Hill Subgroup and basement rocks, as shown in Figure 1 for profile OK-213. In order to create a numerical model, the average values of P-wave velocity and density were obtained from previous studies in the Witwatersrand Basin (Manzi et al, 2012(Manzi et al, , 2015Nkosi et al, 2017;Tucker et al, 2016). To investigate the seismic response of the BLR, the 2D acoustic finite-difference forward modelling was performed using the Tesseral software, with the densities and velocities of the geological units summarized in Table 1.…”

Section: Numerical Modelling and Seismic Reflectivitymentioning

confidence: 99%

Seismic imaging of the gold deposit and geological structures through reprocessing of legacy seismic profiles near Kloof–Driefontein Complex East Mine, South Africa

Mutshafa¹,

Manzi²,

Westgate³

et al. 2022

Geophysical Prospecting

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Two legacy reflection seismic profiles were acquired in 1988, north of the Kloof–Driefontein Complex East Mine in the West Rand goldfield (South Africa), for the purpose of gold exploration and mine planning. These legacy 2D seismic data have been reprocessed using the latest processing tools to improve imaging. Special interest is given to the Black Reef Formation, which hosts a known gold orebody. The original legacy data are of poor quality, especially in areas that are dominated by dolomitic outcrops. To improve the quality of the data, special attention was given to the refraction static correction to enhance the continuity of the reflections below dolomitic rocks. Refraction seismic tomograms from both profiles exhibit three‐layer P‐wave velocity models: (1) topsoil (1000–2000 m/s), (2) a weathered layer ranging from ca. 100 to 300 m in thickness (2000–5000 m/s) and (3) bedrock (> 5000 m/s). Seismic profile OK‐212 shows poor imaging of the Black Reef Formation because of the scattering of seismic energy in the near‐surface due to dolomites from the Transvaal Supergroup, while seismic profile OK‐213 exhibits south‐dipping reflections that are associated with the Black Reef Formation. To improve the structural imaging resolution, we tried pre‐stack time migration, pre‐stack depth migration and post‐stack time migration using the Kirchhoff algorithm. PreSDM most improved the imaging of deeper reflections due to its ability to honour complex lateral variations in the velocity field. Both pre‐stack time migration and post‐stack time migration enhanced the continuity of the near‐surface reflections below the dolomitic rocks.

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Section: Numerical Modelling and Seismic Reflectivitymentioning

confidence: 99%

Seismic imaging of the gold deposit and geological structures through reprocessing of legacy seismic profiles near Kloof–Driefontein Complex East Mine, South Africa

Mutshafa¹,

Manzi²,

Westgate³

et al. 2022

Geophysical Prospecting

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“…Physical property measurements were collected following the procedure described by Nkosi et al . (2017). The main objective was to investigate the potential source of seismic reflectivity of the mineralization (Merensky Reef (MR) and Upper Group‐2 (UG2)) with respect to their host rocks.…”

Section: Physical Property Measurementsmentioning

confidence: 99%

“…Although the ideal conditions for measuring these samples are at elevated pressures (∼ 20–60 MPa) to mimic the in situ environment, our measurements were conducted at atmospheric temperature and pressure. The bulk density measurements were conducted using the water immersion method (based on Archimedes’ principle) (Nkosi et al ., 2017). Another factor that affects acoustic impedance is porosity; however, in this study, we did not conduct porosity measurements as the rock samples are from a crystalline environment and have comparable porosity (Malehmir et al ., 2013; Nkosi et al ., 2017).…”

Section: Physical Property Measurementsmentioning

confidence: 99%

“…The bulk density measurements were conducted using the water immersion method (based on Archimedes’ principle) (Nkosi et al ., 2017). Another factor that affects acoustic impedance is porosity; however, in this study, we did not conduct porosity measurements as the rock samples are from a crystalline environment and have comparable porosity (Malehmir et al ., 2013; Nkosi et al ., 2017).…”

Section: Physical Property Measurementsmentioning

confidence: 99%

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Cost‐effective in‐mine seismic experiments to image platinum deposits and associated geological structures at Maseve platinum mine, South Africa

Rapetsoa

Manzi

Westgate

et al. 2022

Near Surface Geophysics

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The detection of mineral deposits and their related geological structures is of great importance to the mining industry as structures (such as dykes and faults) can affect the safety, cost and efficiency of mining. With the goal of testing cost-effective seismic methods for mineral exploration and mining, active and passive seismic experiments were conducted at Maseve platinum mine in the Bushveld Complex (South Africa) in 2020. The experiments involved surface-passive (using 5 Hz wireless nodes; single vertical component) and in-mine active reflection seismic surveys (using 4.5 Hz land streamer and 5 kg sledgehammer) to image geological structures and delineate economic platinum-group elements bearing Merensky and Upper Group-2 chromitite layers (known as reefs). This paper presents only the results from the in-mine active seismic experiments. The in-mine seismic surveys consisted of seven 2D reflection seismic profiles in the development tunnels, which were located ∼550 m below ground surface and a few tens of metres above known mineralizations: the Upper Group-2 and Merensky Reef. The data were carefully processed to enhance the reflections and suppress noise generated by mine infrastructure (e.g., equipment and ventilation). We successfully imaged the Merensky Reef and Upper Group-2 orebodies approximately 55 m and 124 m below the tunnel floor, respectively, and delineated faults and dykes that crosscut them. Furthermore, the seismic data reveal relatively strong amplitude and faulted reflections below the Upper Group-2 that may represent deeper chromitite-enriched orebodies. However, the economic value of these horizons can only be confirmed through drilling. The processed seismic data were combined with borehole data, synthetic modelling and geological models to constrain the interpretation. This study encourages the use of in-mine seismics for future mineral exploration, mine development and planning.

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“…There are some metal mines exploiting a depth of over 4500 m; for instance, the Mponeng Gold Mine in South Africa has already reached a depth of 4800 m [3,4]. In the early 1980s, coal resources in such countries as Germany, France, Japan, Poland, the former Soviet Union, and the United Kingdom were mined at depths exceeding 1000 m [5]. In fact, a similar advance to more considerable depths has been observed in China: thirty-two metal mines and forty-seven coal mines have been developed at mining depths over 1000 m [6], such as the Hongtoushan Copper Mine in Fushun and the Suncun Coal Mine in Xinwen having mining depths of 1600 and 1500 m, respectively.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Set of Cooling Measures for the Overall Control and Reduction of High Temperature-Induced Thermal Damage in Oversize Deep Mines: A Case Study

et al. 2020

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The mining process in deep mines occurs at elevated temperatures and thus is significantly jeopardized by the thermal damage. In this study, the main factors causing high-temperatures under particular mining geological and prevailing conditions of coal mine production, namely for the Longgu Coal Mine (LCM) in Shandong Province of China, were specified and analyzed in detail. This included exothermic heat from the surrounding rock of an underground roadway, inflow of high-temperature water, seasonal temperature rise, mechanical and electrical equipment operation, and airflow compression in the mine. The integrated artificial cooling mode was implemented on the basis of the original normal ventilation and cooling facilities of the LCM, which involved cooling by mobile refrigeration units, water source heat pump refrigeration units, and a ground centralized ice-cooling radiation system, as well as the underground centralized cooling system provided by Wärme-Austausch-Technik (WAT) GmbH. Eventually, a comprehensive set of measures for the overall control and reduction of high-temperature-induced damage was realized, which ensured more effective cooling of the LCM. Thus, the average temperature of the main operation sites was reduced by 8 K, while that of the underground working faces was maintained at 299.15 K. These measures also resulted in excellent technical and economic benefits: the total three-year increase in revenue and savings reached 76.3 million USD, hence relevant findings of the study are expected to provide technical guidance on the treatment of high-temperature-induced damage in deep mines.

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Experimental measurements of seismic velocities on core samples and their dependence on mineralogy and stress; Witwatersrand Basin (South Africa)

Cited by 8 publications

References 43 publications

Seismic imaging of the gold deposit and geological structures through reprocessing of legacy seismic profiles near Kloof–Driefontein Complex East Mine, South Africa

Seismic imaging of the gold deposit and geological structures through reprocessing of legacy seismic profiles near Kloof–Driefontein Complex East Mine, South Africa

Cost‐effective in‐mine seismic experiments to image platinum deposits and associated geological structures at Maseve platinum mine, South Africa

A Comprehensive Set of Cooling Measures for the Overall Control and Reduction of High Temperature-Induced Thermal Damage in Oversize Deep Mines: A Case Study

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