Master Dissertations

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A study of petrophysical properties of the lake beds of the Rukwa basin based on well log data
(The University of Dodoma, 2017) Mtango, Zephania Grayson
Well logging is the practice of making a detailed record of the geologic formations penetrated by the well. The key purpose of well logging is to obtain petrophysical properties of reservoirs such as porosity, permeability, hydrocarbon saturation etc., for hydrocarbon exploration. Logs also tell us about the fluids in the pores of the reservoir rocks. Petrophysical parameters such as effective porosity (Φ), water saturation (Sw), formation water resistivity (Rw), hydrocarbon saturation (So) and formation resistivity (Rt) is evaluated by using the well log data. In the present study, an attempt has been conducted to describe the application of various open-hole logging tools such as gamma ray, sonic, resistivity and calliper logging tools to determine the petrophysical properties of Lake Beds. The present study portrays the interpretation of well log data using the open hole logs in parts of Rukwa Basin. Well log analysis has revealed a range of formation water resistivity (Rw) of 0.0032 Ω-m throughout the well indicating the presence of water-bearing sands in the Lake Beds. Based on Logs (GR log mostly) the Lake Beds were zoned into 6 zones; named A, B, C, D, E, & F in Galula.1 The six zones are identified by using logs at the depth of (7.8 - 256) m, (256 – 354.8) m, (354.8 – 461.5) m, (461.5 – 554.1) m,(554.1- 702.5) m, & (720.5 – 959.2) with average shale volume of (27% - 46.1%), average porosity (10.6% - 17.5%), average water saturation of (22.2% - 33.6%) and average permeability of (0.34mD – 8.6mD) . In both wells Ivuna.1 and Galula.1 the Lake Beds succession in Rukwa basin revealed through this study to have promising porosity for Gas accumulation. However, these zones are found in a very shallow depth with low permeability.
Detection of hydrocarbon seeps using remote sensing technique in the Rufiji onshore basin
(The University of Dodoma, 2017) Mruma, Abas
Hydrocarbon seeps cause chemical and mineralogical alterations at the surface, which can be identified geologically but also detected by remote sensing techniques. This work aimed at detecting mineral alteration induced by hydrocarbon seeps in a sandstone formation in Rufiji basin (Wingayongo), South Coast Tanzania. For this study, rock samples collected during fieldwork were petrographically analysed and the multispectral ASTER data was downloaded and utilized to characterize the identified alteration minerals in the Wingayongo sandstone. The area is covered by medium-grained gray to brown chocolate bituminous sandstone, which acts as reservoir rock but with no cap rock overlaying it. The contact between sandstone layers was identified and defined as the main source of hydrocarbon migration pathways. The large area of this sandstone is bleached indicating discolouration of ferric iron into ferrous iron. Elemental sulfur greenish yellow in colour together with sulphur smell was identified around the seep. Petrographic analysis (XRD and Thin Section) have shown the high value of ferrous iron but there was no evidence of clay (kaolinite) or carbonate minerals. Remote sensing spectral signature through band ratio enhancement indicated the presence of siderite material, altered vegetation together with un-vegetation signals. The observed signals are potential vectors for oil seeps. Other prospective areas were identified using similar spectral signals in the surrounding areas. The use of more than one data-set together with the use of a more powerful remote sensing technique is recommended to overcome challenges in interpretation and issues of scale of alteration and other controversors.
Sedimentologic and paleocurrent analysis of the early triassic strata in the Ruhuhu basin, Tanzania
(The University of Dodoma, 2017) Syprian, Audax
Ruhuhu basin has eight informal lithostratigraphic units, termed the K1 to K8. This research was conducted at Lifua Member (formally K8). The beds are of Early Triassic and are the youngest stratigraphic unit of the Karoo strata in the Ruhuhu Basin. This research applies sedimentology and paleocurrent analysis of the early Triassic strata in interpreting provenance, shape and orientation and reconstructing palaeogeography of this unit. It involved description, measurements and sampling of the rocks from the outcrops as well as grain size analysis, geochemistry and petrographic studies. Based on the present study, about five lithofacies were identified namely Massive matrix supported para-conglomerate (Gmm), Massive sandstone(Sm), Parallel-horizontal lamination (Sh), Planar cross beds (Sp) and fine silt, mud and clay (Fl). Most of the sandstone exhibited normal grading caused by a decrease in energy of the river current. Grain size analysis indicates that sandstone is moderately sorted, finely skewed, mesokurtic and that most of the grains are silty sand. This two suggestfluviatile dominated by sand channel deposition environment. Grain size analysis and petrography classified the sandstone as sublitharenite and chemically as ferruginous quartzose. The maturity level is from sub-mature to mature sediments, which suggest the source area was of low relief and warm, humid climate where chemical weathering was moderately intense. Geochemistry and Heavy mineral suit suggested basic igneous rock as the provenance of the sandstone. Paleocurrent was from NW towards SE, although some were also from the various localized area. The shape of the basin is elongated NE/SW. Based on the observations, Lifua Member has a good reservoir rock due to the dominant mode of channel deposit and textural characteristics of the sandstone.
Structural framework and its effects on traps formation in the south-eastern part of Rukwa basin
(The University of Dodoma, 2017) Mahwa, Joshua
This work presents the first detailed, structural framework, characteristics and types of traps which are found in the South-Eastern part Rukwa basin, located in the Western Branch of the East African Rift System, South-Western Tanzania. The goal of this work is to examine the structural framework which controls trapping characteristic of the Rukwa basin within the Karoo and Lower Lake Beds reservoir. 2D seismic datasets that were collected in 1983 by Amocco obtained from TPDC were analyzed by using Petrel software and the major structures and stratigraphic sequence were traced and interpreted to characterize the shape and the extent of the structures such as faults and folds which forms traps. These structures which form traps found within the Karoo formation and in Lower Lake bed formation. Three traps fields have been identified as potential traps in the Rukwa basin which are controlled by faults whereby, fold traps have been identified as minor traps. Rukwa basin has been found to have source rock, reservoir rock, seal rock, maturation of hydrocarbon, high geothermal gradient and identified trap field from this study favour the accumulation of Hydrocarbons within the Basin. The study of migration path of Hydrocarbons in Rukwa basin will guarantee the accumulation of Hydrocarbon in the identified Trap field.
Characterization of triassic hydrocarbon source rocks of the Mandawa basin, Tanzania
(The University of Dodoma, 2017) Godson, Godfray
Mandawa Basin is an onshore pull-apart basin located at the southern east coast of Tanzania and covers an area of 16,000 sq.km, it evolved during Permo-Triassic time by ENE-WSW extensional movements during Gondwana rifting and NW-SE extensional movements resulted from drifting of Madagascar during Jurassic time. Hydrocarbon exploration started in 1952, with the first deep exploration well (Mandawa-7) drilled in 1958 by BP company, thereafter ten exploration wells have been drilled up to date. The report (TPDC) shows that five wells have proven to have oil or gas shows, and five wells are dry without shows of hydrocarbons and have been abandoned. The main aim of the thesis is to characterize the source rocks potentiality and determination of the organic-rich intervals of the Basin, namely, the Mbuo Claystone Member and the Nondwa shales. In order to define a potentiality of source rock. Detailed analysis of characterization parameters should be done, these include; total organic carbon (TOC), maturity level, net-to-gross ratio, and organic matter type by integrating geochemical and well log analysis approaches. The results obtained from this study shows that both Mbuo claystone and Nondwa shales have poor hydrocarbon generation potential in their organic-rich intervals. Using Passey’s method it shows that fair average TOC% values were encountered and less than 0.5 NTG for both Mbuo Claystone and the Nondwa shales using a marginal cut-off value of 0.5 wt.% TOC. The cross plot between derived TOC and geochemical parameters show that the source rocks were not worthy to be considered as potential but also the S1and S2 were independent to the thermal maturity and amount of TOC and mostly below the minimum value (1.0 and 5.0 mgHC/g Rock) for the source rocks to be considered as potential for hydrocarbon generation.
Characterization of the accommodation zones along restraining and releasing bends from analogue modeling simulating the seagap fault, off-shore Tanzania
(The University of Dodoma, 2017) Sadiki, Nasra Hoza
There is poor understanding of geometry and evolution of the accommodation zones along the restraining and releasing bends in strike slip systems. This dissertation focused on characterize the accommodation zones between restraining and releasing bends, with special focus on the influences of syn-kinematic sedimentation and the basement pre-existing structuration by simulating the Seagap fault , Off-shore Tanzania. A set of three scaled sand models were performed, using a basement offset 6.5cm /3cm, 90/90 and 156/126 Stepovers without/with Syn-sedimentation respectively. 7 cm of sinistral displacement was applied during all the models. Vertical sections of the completed models cut for analysis of structures at depth. The experimental results for both models were generating pop-up and pull-apart structures and dip flipping of high angle faults. Study concluded that, firstly comparisons between models and area of study fault orientation and distribution were compatible with a sinistral strike-slip system. The internal structures developed were influenced by syn-sedimentation and pre-existence basement. Even more, oblique accommodation and dip-direction flipping of the main fault produced clear inversion of the structures along the accommodation zones which can potentially have a strong impact on the petroleum system. Future study required a test of different scenarios such as use of ductile basement transition, constrains on fault timing, uplift rate along time and comparison between sandbox analogue models and seismic interpretation.
Structural and sequence stratigraphic framework of Lukuliro area, southernpart of Rufiji trough
(The University of Dodoma, 2018) Marwa, Fredrick M.
This study conducted within southern parts of Rufiji Trough include Lukuliro area which has been potential target for oil and gas exploration since 1980’s years. Within Rufiji trough, the discovery of Wingayongo seeps (onshore) and SongoSongo gas (offshore) attract attention on exploration activities within Rufiji trough. The previous works conducted within Lukuliro area failed to establish traps which are well demonstrated in this study. The structural and sequence stratigraphy framework were established through interpretation of six old 2D seismic data and well data from Lukuliro 1 well by using Petrel version 2013. During this investigation interesting structural features that were revealed to occur within Lukuliro area were including faults such as Listric faults, tilted growth faults, wrench faults and flower structures and small-scale folded structures (anticline). The major faults within Lukuliro area revealed to be oriented in NNE-SSW, NNW-SSE and E-W directions. These faults interpreted from different seismic sections within the study area revealed to form good structural traps. The interesting structural traps suggested to be developed within tilted faulted bocks adjacent to wrench faults and also within flower structures. Structural trap configuration revealed to be constrained by Mtumbei limestone reservoir which became sealed by shale, mudstone, and claystone and siltstone lower Kipatimu formation. However, the structural traps seem to be dominant within Lukuliro area but also the potential stratigraphic features revealed from well log interpretation and sequence stratigraphy interpretation including channel infill, unconformities, toplap and clinoforms are responsible for occurrence and accumulation of hydrocarbons.
Sediments thickness and structural framework of lake Natron basin and their implications for hydrocarbon potentiality
(The University of Dodoma, 2018) Godfrey, Grace
Lake Natron is among the basins of the Eastern branch of the East African Rift located in Northern Tanzania. The main objective of this study was to establish the spatial variation of sediments thickness and to delineate the subsurface structures that control the configuration of the basement and their implications for hydrocarbon potentiality. The study utilized both aeromagnetic and gravity data in achieving the objectives. Two dimension gravity modelling, Euler deconvolution of aeromagnetic data and spectral depth methods were used to determine the thickness of sediments. The structural interpretation of gravity and magnetic data were done by applying processing techniques to the observed data. These techniques include Reduced to pole, Analytic signal, Goussav filter and vertical derivatives of aeromagnetic data. The interpretation suggested that the Natron basin is bounded by fault systems, which are mainly trending NE-SW, NW-SE and NS directions. The estimated depths found to the deeper source of 3.18 km and 4.01 km for the aeromagnetic and gravity data, respectively. These depths found on the northern part of the Lake Natron basin. The thickness of sediments decreases from 3.18 km in the northern part of the basin to 2.75 in the southern part using aeromagnetic data. The results from Euler Deconvolution revealed the maximum depth to basement was ranging from 3 km to 3.5 km. Also the results from Euler Deconvolution showed that the study area has different faults/lineaments mostly trending in the NE-SW direction. The results from gravity modelling have shown the variation of sediments thickness ranging from 1.24 km to 4.01 km within the lake basin. Based on these results the northern part of the study area shows the potentiality of hydrocarbon. Integration of both gravity and magnetic data used in this study with seismic data can assist to confirm the potentiality of hydrocarbon in the lake Natron basin.
Reconnaissance exploration for gold in the Misaki area within the Iramba-Sekenke greenstone belt, central Tanzania
(The University of Dodoma, 2020) Maganga, Zortosy Mpangile
Combinations of geological, geophysical and geochemical techniques have been used to explore gold deposits at Misaki within the Iramba-Sekenke Greenstone Belt (ISGB) in Singida region. The Misaki area is occupied by different rocks including homogeneous coarse-grained granite containing numerous xenoliths (> 5 vol. %), tonalite, K-rich granite and pegmatite, and dolerite dykes. All granitic rocks have been intruded by dolerite dykes, cut by epidote veins and are found juxtaposed to a tonalitic rock. Granitic rocks contain mainly anhedral to subhedral K-feldspar, plagioclase, quartz, biotite, hornblende, muscovite and opaque minerals, whereas tonalite contains similar minerals with relatively large amounts of plagioclase, biotite and hornblende (> 10 wt. %) and no K-feldspar. The rocks are weakly foliated to massive and poikilitic. K-feldspar is perthitic, whereas plagioclases have cores with rim overgrowths. Chlorite, plagioclase, epidote and sericite in the rock formed at the expense of primary minerals under greenschist facies conditions. Aeromagnetic data managed to identify lineaments that crosscut different rocks, from which NE-SW, NW-SE and ESE-WNW trends have been recognized. Results from radiometric data mapped different lithological units by their different K, U and Th contents distinguishing areas occupied by sediments or sedimentary rocks and those underlain by granitoid rocks. Soil geochemical survey has identified gold anomalies of up to 0.2 ppm Au that in parts associated with NE-SW trending lineaments. A follow-up detailed geological mapping work is recommended that would involve trenching and sampling of unweathered rocks, and documentation of geological structures to uncover potential gold deposits of the Misaki area within the Iramba-Senkenke Greenstone Belt (ISGB).
Reconnaissance exploration for gold in the Misaki area within the Iramba-Sekenke greenstone belt, central Tanzania
(The University of Dodoma, 2020) Maganga, Zortosy Mpangile
Combinations of geological, geophysical and geochemical techniques have been used to explore gold deposits at Misaki within the Iramba-Sekenke Greenstone Belt (ISGB) in Singida region. The Misaki area is occupied by different rocks including homogeneous coarse-grained granite containing numerous xenoliths (> 5 vol. %), tonalite, K-rich granite and pegmatite, and dolerite dykes. All granitic rocks have been intruded by dolerite dykes, cut by epidote veins and are found juxtaposed to a tonalitic rock. Granitic rocks contain mainly anhedral to subhedral K-feldspar, plagioclase, quartz, biotite, hornblende, muscovite and opaque minerals, whereas tonalite contains similar minerals with relatively large amounts of plagioclase, biotite and hornblende (> 10 wt. %) and no K-feldspar. The rocks are weakly foliated to massive and poikilitic. K-feldspar is perthitic, whereas plagioclases have cores with rim overgrowths. Chlorite, plagioclase, epidote and sericite in the rock formed at the expense of primary minerals under greenschist facies conditions. Aeromagnetic data managed to identify lineaments that crosscut different rocks, from which NE-SW, NW-SE and ESE-WNW trends have been recognized. Results from radiometric data mapped different lithological units by their different K, U and Th contents distinguishing areas occupied by sediments or sedimentary rocks and those underlain by granitoid rocks. Soil geochemical survey has identified gold anomalies of up to 0.2 ppm Au that in parts associated with NE-SW trending lineaments. A follow-up detailed geological mapping work is recommended that would involve trenching and sampling of unweathered rocks, and documentation of geological structures to uncover potential gold deposits of the Misaki area within the Iramba-Senkenke Greenstone Belt (ISGB).
Land use land cover changes, water quality and locals’ involvement in conserving Kihansi spray toads (Nectophrynoides asperginis), in Kihansi Tanzania
(The University of Dodma, 2021) Sigala, Atuhombye
Biodiversity hotspot areas host global potential for the conservation of wildlife species particularly those that are endemic and critically endangered. This study focused at assessing the land use land cover change (LULCC) of Kihansi catchment and adjacent areas, water quality along the Kihansi River and the involvementof local communities on the conservation of the Kihansi spray toads (KST)(Nectophrynoides asperginis). Landsat images were used to classify and monitor LULCC for 25 years from 1995 to 2020. Also, water quality of KihansiRiver was assessed in terms of pH, turbidity, dissolved oxygen (DO), temperature, total dissolved solids (TDS). Semi-structured questionnaires were used to collect data from the respondents from three adjacent villages namely: Mgugwe, Udagaji and Ukami. Settlements and agricultural land increased by 26.23% and 3.7%, respectively. On the other hand, forest land decreased by a rate of 1.2% per yearbetween 1995 and the year 2020.Cultivation of crops such as paddy and maize were the dominant socio-economic activity (p<0.05). Significant variation for water quality variables was observed (p<0.05) for temperature (Mean ± S.E=25.34±0.31oC), pH (Mean ± S.E.=6.88±0.03) and DO (Mean± S.E. =5.41±0.03 mg/L) among the three sampled zones while human activities such as agriculture significantly influenced water quality (p<0.05). About 98.9% (n=361) of local communities wereheard about KST and the variation across villages was significant (p<0.05). Also 46.03% (n=168) have seen the toads although only 27. 67% (n=101) were able to identify the toads through their physical features. Human activities influence LULCC of KC thereby threatening the KC ecosystem and KST due to habitat loss. Ifnoproper measures are taken for management of the Kihansi River continued increase of TDS from human activitieswilldecreases DO in water, thismay threaten sustainabilityofthe re-introduced toads.This study provides baseline information for land use planning in KC and adjacent areas that consider sustainable conservation of the re-introduced KST which includes establishment of buffer zone around the catchment. It also calls for proper management of the Kihansi River through involvement of local communities to ensure sustainability of the re-introduced KST.Local communities should be involved in conservation activities like habitat restoration and research activities on the re-introduced KST throughconservation education, and outreach programs.
Petrophysical analysis of the red sandstone group of The Rukwa Graben, Southwestern Tanzania
(The University of Dodma, 2021) Ojok, Tonny
The study of various well-logs aids in the identification of potential sand and reservoir zones and their thicknesses within a formation. The current study addressed the lack of research and literature on the petrophysical properties and reservoir potential of the Red Sandstone Group (RSG) Formation in the Rukwa Basin, southwestern Tanzania. This study presents the findings of the petrophysical analysis of the RSG Formation in the Rukwa Rift Basin. The Techlog computer program was used to analyse the Ivuna-1 well-log suite, comprising of the caliper, gamma-ray, neutron, and density logs and the Galula-1 well-log suite comprising of gamma-ray, spontaneous potential, resistivity, and sonic logs. Based on the petrophysical analysis, five sand zones were delineated in each well: (A-E) in the Galula-1 well and (1-5) in the Ivuna-1 well. According to this study, the RSG in both the Galula-1 and Ivuna-1 wells is dominated by clastic facies with interbedded thin shale and was most likely deposited in fluvial and fluvio-lacustrine environments. The delineated sand zones in Galula-1 well have shale volumes ranging from 28.8% to 36.1%, high effective porosities ranging from 30.1% to 32.6%, high permeabilities ranging from 88.45 mD to 121.39 mD, 100% water saturation, and no hydrocarbons. The five delineated reservoirs in Galula-1 well have high effective porosities ranging from 25.8% to 28.8%, high permeabilities ranging between 45.92 mD and 71.91 mD, and are 100% water saturated but lack hydrocarbons. As a result, the RSG of the Galula-1 well was assessed to have good petrophysical properties and is a potential hydrocarbon reservoir given the presence of hydrocarbons. By contrast, the delineated sand zones in Ivuna-1 well have shale volumes ranging from 26.4% to 35.6%, very low effective porosities ranging from 0.011% to 0.038%, and poor permeabilities ranging from 0.007 to 0.117 mD. Further, the two delineated reservoirs in Ivuna-1 well are thin and have very low effective porosities ranging between 0.112% and 0.106% and poor permeabilities ranging between 1.33 mD and 1.64 mD. Consequently, the RSG of the Ivuna-1 well was evaluated as having poor petrophysical properties and is not a suitable hydrocarbon reservoir. This study also revealed that the porosity and permeability of the RSG declines greatly from the Galula-1 well to the Ivuna-1 well. Nevertheless, more research is recommended to validate this revelation. This study further, recommends more research into the porosity and permeability of the RSG through petrography and core analysis. The findings of this study will contribute to academic, geologic, geophysical, and hydrocarbon research of the RSG and Rukwa Basin at large.
Analogue sandbox modelling of the Western Subbasin, Melut Basin, South Sudan: strike-slip tectonic implications for rifting and fault sequences
(The University of Dodma, 2021) Duot, John Bior
Melut basin is a passive rift basin that contains numerous oil-rich rift sub-basins, and it has experienced many strike-slip effects from the Central African shear zone. The multi-directional stresses of strike-slip settings have made western sub basin architecture and fault sequences complex and difficult to understand. The lack of practical structural data might have been one of the reasons for the challenging discoveries of oil and gas in the study area. Therefore, it is essential to deepen the structural data adequacy. The objective of this study is to characterize strike-slip tectonic implications for rifting and fault sequences responsible for the creation of accommodation spaces of Melut rift episodes by using analogue sandbox modelling-assisted approach to promote future exploration in the Melut Basin. Analogue modeling as a method used scales of time and length to model geodynamic evolutions. To enhance structural data adequacy, the experiments were carried out at the laboratory and set with the same basement offset 5.3cm/2.9cm, 158°/151°stepovers in the releasing and restraining bends. The analogue modelling rig was set to be displaced by the computer-controlled motor at a rate of 5mm/2min with 65mm dextral displacement motion. The analysis was done using the top views and vertical sections from the models. The experimental results show delimited uplifts and extensional collapses characterized by oblique faults with normal and thrust components, well deformed pull-apart basins, and redistributed accommodative structures for ExpS1, ExpS2, and ExpS3 respectively. The study found out that the first rift phase reflect large and subsided sedimentary layers filled by 15 mm (1.5 km in nature) and accommodated by the two normal bounding faults while the second rifting revealed less tectonic subsidence filled by 9 mm (0.9 km in the nature) deposits and held by normal bounding and tilted faults, and lastly the third rifting showed the bounding normal fault and the oblique fault with a normal component filled by 6 mm (0.6 km in the nature) sediments thickness. The exhibited trans-tensional pull-apart basin and positive flower structures display economic importance. The findings of this study are useful in the future exploration and production of oil and gas in the study area. Semi-regional seismic and extensional modelling studies are recommended to illuminate structural styles.
Characteristics of graphite mineralization and it’s exploration potential in Chenjere area Ruangwa district south eastern Tanzania
(The University of Dodma, 2021) Moye, Charles Daniel
Electromagnetic and magnetic surveys, geological mapping, trenching, drilling and geochemical analysis were carried out in the Chenjere area to investigate the graphite characteristic and the exploration potential of graphite mineralization. Mtimbo, Matochi, Ng'imbwa, and Nakapelo were discovered to have graphite potential using these approaches. Loss on ignition (LOI) and infrared spectroscope (IR) analysis revealed graphite grades ranging from 4 to 8 wt.%. The graphite zones have thicknesses of 13 to 29 m and strike lengths of 1 to 4 km. The study has revealed that the graphite mineralization zones are concordant with the prominent strike of NE to SW. The electromagnetic signals have shown a positive correlation with the graphite mineralization as the high conducting bodies are coinciding with the graphite mineralization. This is proven by samples from trenching and drilling analysed by the IR method. Petrographic studies have confirmed that the graphite encountered is of flake type disseminated in the host rock of graphitic gneiss. Flakes showed dip-slip lineation similar to those of hosting rocks. Based on the field observation, electromagnetic survey, graphite grade, petrographic studies and comparison with the renowned graphite deposits the Chenjere graphite is of sedimentary origin. The graphite flakes are coarse ranging from 50 to 1000 µm. The lath shape flakes had inter growth with silicate gangue minerals with no overgrowth. The graphite flake size, the grade and the extension are warranting for the economic exploration potential in the Chenjere area
Geochemical evaluation and correlation of source rocks, crude oils and oil seepage. A case: Albertine Graben, Uganda
(The University of Dodoma, 2021) Majorine, Namaganda
Geochemical evaluation and correlation of source rock samples, crude oils and oil seepage samples was carried out in the Albertine Graben, Uganda to establish the existence of a genetic relationship between the Graben’s source rocks and the crude and seepage oils. Evaluation of samples was carried out using data from pyrolysis analysis of samples, while the correlation of samples was based upon the recognition of unique patterns from biomarker analysis. The study involved one (1) seepage, two (2) source rock samples, and five (5) crude oils from Mputa, Kingfisher, Gunya, Ngiri, and Job-Rii wells. The TOC values of the source rock samples ranged from 1.25 to 7.2%, implying that the source rocks had a high potential to generate hydrocarbons. Furthermore, source rock samples with TOC ≥ 0.5% were also evaluated for petroleum potential using petroleum indices of Tmax, S1, S2 and HI. The source rock samples Tmax values ranged between 432 and 447°C, implying that the source rock maturities were within the oil window. The S1 and S2 parameters ranged from 0.02 to 1.78 mg/g rock and 0.87 to 37.71 mg/g rock, respectively, implying that the genetic potential of the source rock samples varied from poor to excellent. Additionally, the HI values ranged between 65 and 523 mgHC/gTOC, implying that the source rock samples were composed of kerogen types II, II/III, and III. Biomarker (terpanes (m/z 191) and steranes (m/z 217)) analysis, pristane/phytane ratios and n-alkane distribution were also performed on source rock samples, seepage, and crude oil samples. The results show that the source rock samples, seepage and crude oils were derived from mixed organic matter dominated by algal deposited in a sub-oxic depositional environment. Oil-oil and oil-source correlation using cross plots and ternary diagrams of steranes and terpanes, indicated that there was a correlation between the crude oils and the oil seepage based on sterane analysis. However, no correlation was observed between source rock samples, and crude oils and oil seepage. Based on terpanes analysis of the study samples, a correlation was exhibited between only one source rock sample (SRE 2) and the crude oils samples. However, there was no correlation shown by all the three study samples: source rock extracts, crude oil, and seepages. The findings of this study will aid in further research and development programs as well as guide the Uganda’s petroleum regulatory authorities and exploration companies on the hydrocarbon potential of the Albertine Graben.
Delineation of lithologies and subsurface structures related to gold mineralization in Kibati prospect Mvomero, Morogoro: Implications for gold exploration
(2023) Balambirwa, O
Structures, lithologies, and potential zones and their relationship to gold mineralization were investigated to decipher the controls of gold mineralization at the Kibati Gold Prospect. The structures and lithologies were investigated through the interpretation of high-resolution aeromagnetic data, ground magnetic data, geological mapping, and rock sampling. Aeromagnetic results reveal the presence of two structural systems that trend in NW-SE and NE-SW, whereby the NW-SE is the dominant control of gold mineralization. The subsurface structure with NW-SE trending controls the mineralized fluids as a consequence of gold mineralization in the surface lithologies. Results from the detailed investigation in two blocks A and B within the study area show that most of the structures trend in the NW-SE direction. Petrography and field observations show that granitic gneiss, garnet biotite quartzo-feldspathic gneiss, dolerite and amphibolite are the main exposed outcrops. The quartz vein shear zone hosted with hematite-limonite is associated with auriferous veins characterized by gold values ranging from 0.004 to 19.680 g/t. Exposed quartz veins in the northern part of the Kibati area also returned gold values of up to 0.623 g/t. The gold anomaly is persistent and collinear with the NW-SE trending structures delineated from magnetic maps. The trend of the structures in blocks A and B overlaid with gold anomalies range from 0.0623-4.419 g/t and 10.19-19.680 g/t respectively, which confirm the target zones located within shear zones hosted quartz vein striking NW-SE of Kibati prospect. These structures, therefore, act as conduits where gold precipitated in minor/local structures in blocks A and B.
Characterization of feldspathic deposits at virundiko area, Gairo district in central East Tanzania: implication for industrial viability
(The University of Dodoma, 2023) Francis, V.
The Virundiko area is within the Mozambique belt which is highly occupied by metamorphic rocks mainly ganertiferous migmatitic biotite gneiss, within the pegmatites where big crystals of feldspar, mica and quartz are found. The pegmatite extends to about 15 to 20 meters thick. Partly, garnet amphibolite lithologies forms elongated lenses concordant to the main foliation of the area. Currently, there is no any study established regarding the suitability of feldspathic deposits within the area for industrial viability. Geochemical, mineralogical, physical and optical properties analyses are the techniques that have been used in this study to identify the industrial viability of the feldspathic deposits at Virundiko area in three sites namely KST1, KST2 and KST3). The ratio of K2O/Na2O in feldspathic deposits in all three sites is greater than 1, suggested that the traditional method of ceramic production. However, for saving cost modern technologies should be considered with the condition of minor mineral beneficiation to decrease the ratios of K2O/Na2O to be less than 1, this applies also in glass industries. It is stipulated that the feldspar deposit at Virundiko fits best in porcelain and high-voltage electroporcelain. Minor removal of coloring oxides (TiO2 and FeO2) should be done for white vitrified bodies such as white porcelain and glass. There is very low amount of calcium within the samples hence the deposits do not fit for electronics and biochemical equipments. The mineralogical analysis indicates that the samples are predominantly K-feldspar with big crystals of feldspar which ranges from 5cm to 20cm with few mica and quartz grains associated with positive geochemical analysis results suggestive for gemstones. Moreover, the physical tests indicate that, the minerals are of moonstone variety showing translucently milky white which are smooth when cut with durable without any fractures and cleavage joints. The feldspar minerals are moderately hard, the optical character of the samples displays adularescence phenomena with double refractive which add value to the beauty of these minerals when cut as a gem. Therefore, the results support that samples from all three sites fit for gemstone in a cabochon cut.
Assessment of structural evolution of the southern kilombero rift basin, Tanzania: Implications for hydrocarbon potential
(The University of Dodoma, 2023) Richard, G.
In recent years, rift basins, including the southern Kilombero basin, have gained significant interest due to the discovery of oil in the East African Rift System, include the Albertine graben in Uganda and the Lokichar basin in Kenya. Although the southern Kilombero rift basin has been little studied using few widely spaced 2D seismic lines, there is a lack of detailed information regarding the structural pattern and kinematics, as well as their relationship with the southern Kilombero rift border fault. Therefore, this study focuses on the structural evolution of the southern Kilombero rift by conducting morphostructural and paleostress analysis to establish important fault parameters, including the current rift kinematics. The study uses SRTM-DEM, fieldwork, literature reviews, seismic interpretation and sandbox modeling in order to simulate the faulting sequences and their pattern with time. The results of the morphostructural analysis have revealed that the southern Kilombero rift border fault is a nearly 100 km long, symmetrical rift segment characterized by vertical displacement ranging from 250 m to 1300 m. The current seismic activity in the area is controlled by NNW–SSE trending normal faults. The analysis and interpretation of the results of the modeled stress tensor indicate that the stress regime is predominantly extensional being characterized by normal faulting and a horizontal minimum stress axis of approximately (Shmin) 060˚, suggesting that the southern Kilombero rift is an oblique rift. The sandbox model reveals that the southern Kilombero rift basin is transitioning from a half-graben into a full-graben, signifying an essential structure for hydrocarbon accumulation, fluid migration and preservation. During syn-kinematics rifting, the extension of the border fault led to the formation of numerous minor structures, increased accommodation space, relay ramps, en-echelon fault segments and intrabasinal structures. These structures contribute greatly to the basin’s evolution. Correlation between the 2D seismic data and the sandbox model suggests that sandbox modeling outperforms seismic data in identifying and interpreting complex, minor and structural features in subsurface geology. The discovery is anticipated to motivate geoscientists to explore more potential hydrocarbon resources in the future for economic gain.
Reconstruction of the rift formation and kinematics for the evolution of the basins in the afar region
(2023) Nyarera, Nyangena D.
This study focuses on seafloor spreading and evolution of the Afar region since the Paleogene through an integrated investigation of magmatism, continental rifting and seafloor spreading processes. While previous studies have attempted to establish rifting initiation on a local and regional scale, none have simulated the exact timing of the Afar rifting, rift basin evolution and magmatism over time. The study utilized geophysical and geological data incorporated into Gplate software to establish the tectonic evolution of magmatism, the timing of initial continental rifting and the spatial-temporal evolution of magmatism over the past 65 Ma. Seafloor spreading rates were estimated and validated against magnetic anomaly profiles from published data. The findings reveal that magmatism started at 31 Ma and manifested in four episodes. The rifting between the Arabian and Somalian plates began at 19 Ma, leading to subsequent drift in varying velocities and directions. The Arabian plate initially moved northeastward before undergoing a significant counterclockwise rotation towards the north-northwest. In contrast, the Somalian plate initially moved south-southeast and later rotated counterclockwise towards the east. These movements can be attributed to tensional forces at plate boundaries, interactions with neighboring plates, and the influence of mantle convection. The Seafloor spreading rates in the region range between 12.29 mm/yr and 20.12 mm/yr and exhibited a dominant orientation of E-W direction. Seafloor spreading started ca.16 Ma and has continued to the Present. The study also has identified an average pole relative motion between the Somalian and Arabian plates at 10.5469N 35.1857E, with an average angular rotation of 0.5353°/Ma. Moreover, the spreading direction from the south pole show an average angle of less than 30°, indicating a shift from east to west. This work will aid in understanding the mechanisms that drive tectonic plate movement and assessing the role of volcanic activity and sedimentation in the potential development of hydrocarbon resources in the basins of the Afar region. Additionally, the findings provide valuable insights on the geological history and evolution of basins in the Afar region hence more integration studies are required to determine sedimentation rates, why the Arabian plate exhibited a higher rate of plate motion than the Somalian plate and also to evaluate the hazardous implications associated with high rates of plate rotations to safeguarding local communities and infrastructure.
Characterisation of Handali gold mineralization-Dodoma region, central Tanzania
(The University of Dodoma, 2023) Mallya, Godfrey J.
The study on the characterisation of gold mineralisation in the Handali area covers the aspect of gold hosting lithologies, structural control and elemental associations. Geophysical geological and geochemical techniques are used to establish the extent of gold mineralisation in the Handali area. Gold occurrences of Handali have shown an association with interpreted NW-SE shear structure that coincides with the linear magnetic low zone. Artisanal pit mapping and petrographic study of samples from these pits indicate that gold mineralisation is characterised by quartz ± feldspar veins/ veinlets in multiple zones confined to amphibolite. The main ore minerals are pyrite and chalcopyrite, with insignificant content of bornite and covellite. Alteration minerals are chlorite and sericite. Analytical results of rock samples from Artisanalpitsshow0.2 g/t Au in amphibolite, while sulphide-bearing quartz ± feldspar vein amphibolite returned up to 8.5 g/t. Gold concentration in the rock samples show moderate to strong correlation with Cu, As and W as shown by Pearson Correlation coefficient and Hierarchal Cluster Analyses (HCA), indicating this element suite is potentially proposed to be used as pathfinder elements for future exploration of gold. Geochemical results of soil samples returned gold anomalous values of up to 0.123ppm.Principle Component Analysis (PCA) of soil geochemical data shows that Fe, Cu and Zn are the main pathfinder elements while searching for gold in the area. The bubble plot of Au values generated from soil geochemical data delineates NW-SE and defines new NE-SW trending patterns extending Handali-type gold mineralisation. Lithological, structural and geochemical studies demonstrate the relationship between lithology, structure and gold mineralisation. Soil sampling and detailed structural mapping are recommended before any attempt to conduct drilling to the Handali prospect.

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