Doctoralhttp://localhost:8080/xmlui/handle/123456789/1982023-03-30T17:17:58Z2023-03-30T17:17:58ZKNUST consumes Ghc 2.4m electricity monthly: it uses energy inefficient appliancesDonko, Kwadwo Baffoehttp://localhost:8080/xmlui/handle/123456789/5862023-02-24T14:32:52Z2019-01-28T00:00:00ZKNUST consumes Ghc 2.4m electricity monthly: it uses energy inefficient appliances
Donko, Kwadwo Baffoe
2019-01-28T00:00:00ZRisk analysis for discount rate determination in mineral development project: a case studyDzimah, Emmanuelhttp://localhost:8080/xmlui/handle/123456789/3682023-01-30T16:18:36Z2020-06-01T00:00:00ZRisk analysis for discount rate determination in mineral development project: a case study
In Ghana alone, Newmont Ghana owns two subsidiaries, Newmont Ghana Gold Limited which operate the Ahafo North and South project and Newmont Golden Ridge Limited which operate the Akyem mine. The Ahafo South mine which has been in operation since 2006 was given permit to start developing another concession, the Awonsu project. As a result, there was the need for the company to evaluate the economic viability of mining this concession using NPV evaluation method which has discount rate as one of its parameters. The development and exploitation of a mine comes with risks and heavy capital investment with longer payback periods. It is therefore important to consider risk when evaluating a mining projects by calculating a risk premium that will compensate investors for taking additional risks in a mineral project.Without a risk premium, Strategic Mine Planners face a challenge of setting an appropriate discount rate for use in NPV project evaluation while investors will also appreciate risk premium which when added to a risk-free rate of return (Interest rate) to get an adjusted-discount rate will compensate these investors for extra risk taken.
Some major inherent risks such as technical (grade estimation), economic (varying metal prices) and political risks (tax, environmental regulations) and their accompanying probability and impact scores were identified through questionnaires and these two values multiplied to get a risk value for each risk identified. The risk values for each of the risk were summed up to get an overall risk value which was then converted into a risk premium of 9% for the project. An adjusted-discount rate of 28.8% was finally calculated by adding a risk-free rate of return (bond rate) to the risk premium of 9%.
The adjusted- discount rate of 28.8% determined represent the returns that compensate investors for extra risk taken when they decide to ignore other investment instrument and choose this project. With this, investors are now better placed to make sound investment decisions on projects. The researcher therefore recommends that mining companies in Ghana should use a discount rate that is between 25.8% and 39.8% for their mineral projects.
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2020-06-01T00:00:00ZReview of the Ahafo South Mine blasting procedures to achieve zero bouldersAckom-Ghansah, Michaelhttp://localhost:8080/xmlui/handle/123456789/3672023-01-30T16:29:32Z2020-07-01T00:00:00ZReview of the Ahafo South Mine blasting procedures to achieve zero boulders
Obtaining a good fragmentation for every blast remains an ever-important discussion in the mining parlance as it is the first step towards mineral recovery. Achieving the required fragment sizes with the maximum size (p100 value) being less than 1000 mm after blasting is a major challenge in Newmont Ahafo South Mine. Blasting usually results in excessive proportion of boulders which negatively affect productivity by increasing the time taken for loading, hauling, and crushing. It also increases the cost of operation because of secondary blasting and the fines also result in loss of gold.
Helping the Mine achieve its initiative of zero boulders will positively impact productivity and reduce the cost of operation. The objective of the study is to review the current blast design procedures adopted by Ahafo South Mines in order to identify the causes of the boulders and to optimize the design parameters if necessary, in order to obtain the required fragmentation for the Mine. For this reason, a quality assurance and quality control were done on the existing drilling and blasting procedures to identify the mistakes and optimized (modified) drilling and blasting parameters was obtained through a simulation using the Kuz-Ram Model.
Digital images from the blast shots were taken and analyzed using the Orica Shotplus software and the average result of the two blocks were compared to results from the Kuz-Ram Model. Because of the Kuz-Ram model’s strong predictability, it was used to predict the blast design parameters that would yield optimal fragmentation without any boulder. The image analysis showed an average variation of 16.4% of the expected fragmentation which aided in obtaining an expected maximum size as 603.4 mm other than the 517 mm from the prediction model.
Thus, the Kuz-Ram model was used to predict spacing and burden of 4.2 x 3.5 m (with a powder factor of 1 kg/m3) as the optimal blast design parameter to achieve the Mine’s Initiative
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2020-07-01T00:00:00ZThe geology and physico-chemical characteristics of the hydrothermal gold mineralisation at the Damang gold deposit, Ghana.Bani Fiadonu, Etornamhttp://localhost:8080/xmlui/handle/123456789/3262023-01-20T13:31:29Z2019-06-01T00:00:00ZThe geology and physico-chemical characteristics of the hydrothermal gold mineralisation at the Damang gold deposit, Ghana.
Bani Fiadonu, Etornam
The Damang gold deposit is located in the Tarkwaian within the structural basin of the Ashanti belt of Ghana. The Damang deposit features an anticline with its western limb displaced downward to the south by a major fault and the eastern limb that predominantly host most of the gold. The anticline plunges 15°- 33° NNE. The beddings of the host sediments dip from about 30° to 70° to the east and have a strike length of about 3km and extends 100m. The deposit is hosted in the Tarkwaian rocks where an earlier conglomerate paleoplacer gold in the Banket Series is over-printed by a later hydrothermal gold. The hydrothermal gold exhibits a post-peak metamorphosed and structurally controlled brittle-ductile deformation such as brecciation, fractures and micro-folds observed in the field and in diamond cores. Deformation effect is demonstrated by subgrain textures observed in quartz grains in thin sections. The mineralisation is associated with sub-horizontal quartz – carbonate veins which cut across all the lithologies in the Damang area, and hence, epigenetic.
Two main dolerite dykes and other numerous minor dykes and sills traverse the deposit. These intrusives are inferred to be associated with calc-alkaline tholeiitic basalt magma in an Island Arc tectonic setting, whiles the sediments are derived from recycled Orogeny provenance.
Chemical signatures and mass balance transfer calculations show that major elements associated with the hydrothermal alteration involve the enrichments of Au, Ag, Ba, Rb, MgO, CaO, and significant depletion of SiO2 and minor depletion of Na2O.
Important physico-chemical characteristics associated with the mineralisation such as temperature, trapping pressure, fluid salinity and composition, mechanism of gold transport and deposition, and source of the ore fluids have been determined by this study. The mineralising ore fluid is an aqueous-carbonic fluid with other constituents of H2S, SO2 and minor amounts of CH4. Little or no N2 was detected by Raman spectroscopy and this is contrary to previous literatures on hydrothermal gold in other parts of the Birimian, which reported the presence of N2 gas as constituent of the ore fluid. The CH4 content may be attributed to localised hydrolysis reaction between carbonaceous sediments and the ore fluid. Two sets of salinities were recorded: a low salinity of 1.0 to 2.6 wt % NaCl equiv. and intermediate salinity of 2.4 to 8.9 wt % equiv. of NaCl, which may be attributed to fluid immiscibility from a homogeneous magmatic-metamorphic fluid. Independent temperature estimates from chlorite and Ti-in-biotite geothermometries indicated a temperature range of 200 ºC to 500 ºC as the possible temperature for the hydrothermal gold emplacement, and fluid inclusion gave a temperature range of 250 ºC to 400 ºC and pressure range of 0.70 – 2.00 kbar based on fluid inclusion isochore calcualations using bulk density of 0.70 - 0.89 g/cm3 from CO2 homogenisation temperatures and salinities of aqueous inclusions.
The close association of gold with sulphides (especially pyrite and pyrrhotite) and the low salinities (≤ 10 wt % NaCl equivalent) of the mineralising fluids suggest that the gold was transported in solution as bisulphide complexe (Au (HS)2 – ) under reducing condition.
Stable isotope constraints for the mineralising quartz vein indicate the following range for the hydrothermal fluid; 18 Ofluid values range from 9.1 to 10.3 ‰, which is consistent with fluid derived from regional metamorphic devolatisation (metamorphic fluids) and/or magmatic hydrothermal fluids. However, the low salinity precludes a magmatic source. The range in C for the non-mineralised carbonate and the mineralised carbonates is -2.0