Faculty of Geosciences and Environmental Studies
http://localhost:8080/xmlui/handle/123456789/217
FGES2024-03-28T09:40:56ZHydrogeological Studies in the Tarkwa Mining Area
http://localhost:8080/xmlui/handle/123456789/811
Hydrogeological Studies in the Tarkwa Mining Area
Seidu, Jamel
The Tarkwa mining area, which forms part of the Ankobra River basin has over 100 years of
history of mining, predominantly gold and manganese. Two main rivers that drain the area are
the Huni River to the north and the Bonsa River to the south. Over the past decade, there has
been a proliferation of boreholes and hand-dug wells in the area, in response to the growing
deterioration of the surface water that served as a source of water supply for the Tarkwa
Township. Geophysical investigations have been conducted in the area to locate features that
are related to groundwater occurrence, and the results of these individual studies are stored in
the archives of the mining companies. In this thesis, these individual results are collated and
re-analysed as one composite document to create a more unified database for a better
hydrogeophysical investigation.
The overall aim of this PhD thesis is to integrate available historical ERI geophysical data to
develop a conceptual groundwater potential model and also develop a hybrid groundwater
level prediction model using signal decomposition and an optimised extreme learning
machine.
Three different signal decomposition techniques: wavelet transform (WT), empirical wavelet
transform (EWT) and variational mode decomposition (VMD) were initially applied to
hydrometeorological data to denoise input data (precipitation, temperature and evaporation).
Afterwards, the denoised signals were used as input and fed to the self-adaptive differential
evolutionary extreme learning machine (SaDE-ELM) algorithm to create the resulting hybrid
models of WT-SaDE-ELM, EWT-SaDE-ELM and VMD-SaDE-ELM.
Prior to the development of the hybrid groundwater level model, the impact of data partition
on groundwater level prediction was explored. This was done by testing five partition
percentages using the traditional hold-out cross-validation, popularly known as the “train-test”
data partition. The partitions used are 50-50, 60-40, 70-30, 80-20 and 90-10 representing
training and testing percentages in each case. These partitions were tested on four different
traditional artificial neural network methods, namely: Backpropagation Neural Network
(BPNN), Radial Basis Function Neural Network (RBFNN), Generalised Regression Neural
Network (GRNN) and Group Method of Data Handling (GMDH). Statistical indicators of
Root Mean Square Error (RMSE), Normalised Root Mean Square Error (NRMSE) and Mean
Absolute Percentage Error (MAPE) was used to make an objective evaluation.
Results indicate that the hybrid models created performed excellently, as compared with very
potent metaheuristic methods in literature like particle swarm optimisation - artificial neural
network (PSO-ANN), genetic algorithm – artificial neural network (GA-ANN) and SaDE ELM. Thus, the superiority, consistency and efficacy of the hybrid models are attributed to
the application of the signal decomposition on the input variable coupled with its application
to an optimised extreme learning machine
2022-09-01T00:00:00ZPetrography and geochemistry of Tarkwaian quartzites at Amoanda Pit and banket conglomerates at saddle pit and their relationship with mafic intrusives in the area
http://localhost:8080/xmlui/handle/123456789/340
Petrography and geochemistry of Tarkwaian quartzites at Amoanda Pit and banket conglomerates at saddle pit and their relationship with mafic intrusives in the area
Teye, Emmanuel Kofi
Thin and polished sections of thirty-six rock samples from Amoanda Pit in the Tarkwaian
showed that the banket footwall quartzites contain mainly quartz, chlorite, plagioclase,
amphibole and minor sericite, epidote, chalcopyrite, pyrite, magnetite, hematite and trace
gold. The protoliths of the rock were probably sublitharenite, feldspathic litharenite and
litharenite. Overlying banket conglomerate at the Saddle Pit is oligomictic or polymictic
with large rounded pebbles and moderately sorted quartz, chert, schist, and hornstone; the
matrix is made up of quartz, plagioclase feldspars, sericite, chlorite, garnet and amphiboles.
At the Saddle Pit, diorite sills and dykes contain mainly plagioclase feldspars, amphibole,
chlorite, sericite and quartz with minor epidote, biotite, garnet, pyroxene, pyrite, pyrrhotite
and chalcopyrite. Pyrite is partially altered to secondary hematite and magnetite. The
intrusive heat might have introduced secondary amorphous gold other than the palaeoplacer
granular gold in the banket footwall quartzite and the conglomerate. Post placer gold was
secondary mainly at the contacts with diorite and associated with second generation
hematite and magnetite. Generally the rocks were affected by greenshist facies
metamorphism which post-date peak amphibolite facies. Whole rock XRF analyses show
Al2O3 range from 6.86 to 26.6 wt% possibly due to plagioclase which is partially altered to
sericite and quartz. Eu anomaly values are greater than 1 probably due to plagioclase
accumulation while high total REE could be due to high alteration of the rocks.
x,105p; ill.
2021-10-01T00:00:00ZDesign of optimal slope parameters for the proposed Kobeda Pit at Gold Fields Ghana Limited, Tarkwa Mine
http://localhost:8080/xmlui/handle/123456789/332
Design of optimal slope parameters for the proposed Kobeda Pit at Gold Fields Ghana Limited, Tarkwa Mine
Balegha, Mohammed Mwene Soma
Tarkwa Gold Mine (TGM) is depleting its reserves to the east of the mine. It has, as a result embarked on vigorous near mine exploratory work to the west of the concession for reserve generation. Results indicate gold mineralisation of economic interest. TGM seeks to provide slope design that would satisfy shareholders and employees in the context of safety, ore recovery, and financial returns for the proposed Kobeda Pit.
Rock Mass Rating (RMR) and subsequent adjustment to obtain the Mining Rock Mass Rating (MRMR) was done for rock mass characterisation. The rock mass ratings for the various geotechnical zones ranged from 40.91 to 67.72 and rated from fair to very good.
Kinematic stability analyses were performed for all the three design sectors using stereographic techniques to determine the failure modes that are kinematically possible in bench and/or multi-bench scale slopes. Multi-bench scale planar and wedge failures are kinematically possible in all sectors.
Limit equilibrium analysis gave factors of safety that exceeded the minimum acceptable factor of safety of 1.05 for completely weathered material and 1.20 for fresh rock. The probability of failure was however less than 5%.
Pit wall architecture for the geotechnical domains were 8 meters, 18 meters, 75 degrees for the berm width, bench height, and bench face angle respectively. Indicative overall slope angles fell between 50.02 to 59.21 degrees and rated from fair to very good.
ix,147p; ill
2019-05-01T00:00:00ZPetrography and geochemistry of Akyem Mine gold deposit, Ashanti belt-Ghana
http://localhost:8080/xmlui/handle/123456789/331
Petrography and geochemistry of Akyem Mine gold deposit, Ashanti belt-Ghana
Omari Somuah, Agyapong
Petrographic and geochemical investigations on rocks that host the Akyem Mine gold deposit situated in the north eastern flank of the Ashanti Belt, Ghana were used to determine the lithologies and textures within the host rocks and ore zone. The work also studied the styles of alteration and mineralisation and their relationship. The rocks generally are fine to medium grained, weakly to strongly foliated with mineral compositions dominantly made up of plagioclase, amphibole, chlorite and quartz with moderate sericite, epidote, dolomite, calcite. Ore minerals such as pyrite, pyrrhotite, magnetite, arsenopyrite, gold and chalcopyrite occur in the deposit. Appropriate rock names could be amphibole-chlorite schists and quartz-chlorite schist. The primary minerals are strongly altered leaving relict bytownite, therefore the rocks are subjected to geochemical classification. Geochemical data in wt % SiO2 (39-62.5, average 54.19), Al2O3 (9.44-19.4), Na2O (0.51- 8.64), total FeO (4.37-14.2), CaO (0.48-10.6), MnO (0.07-0.22), MgO (1.13-6.31), and TiO2 (0.39-1.33). The values were used in discrimination diagrams to deduce protoliths of andesite to sub-alkaline basalts. The altered rocks in the Akyem Mine deposit exhibit varying intensity of silicification, sulphidation, sericitisation, carbonatisation and albitisation, so, were categorised based on the extent of alteration. Hence, weakly altered rocks contain alteration package of dolomite-calcite-chlorite-sericite with gold up to 0.98 g/t. Moderate to highly altered rocks are characterised by silica-albite-calcite-epidote with gold grade >0.98 g/t. Two generations of gold, pyrite and arsenopyrite occur respectively. Both generations of gold are more closely associated with fine anhedral pyrite 2 and arsenopyrite 1 and 2 respectively. Gold 1 is fine grained and may also occur along sheared quartz veins whilst Au 2 is medium grained and usually overprint these veins.
x ,73p; ill.
2019-03-01T00:00:00Z