by Ogagarue D.O.
Original Research
Imaging of the shallow Pliocene channels in a legacy streamer 3D seismic dataset acquired in a Niger Delta shallow marine environment posed a serious challenge due to the presence of shallow gas-charged zones in the dataset, making the data sub-optimal for further exploration and field development. Acquisition of modern high quality 3D streamer data over the area was no longer feasible owing to dense facilities and field activities in the area. To maximize exploration potential especially of the deeper targets, a high density multicomponent seismic dataset was acquired over the area. Processing of the converted wave derived from the multicomponent data was very challenging due to the special binning requirement which relied heavily on the accuracy of the ratio of the compressional to converted wave velocities. This paper focuses on the velocity model building and imaging of the converted wave to adequately resolve the lateral inhomogeneities associated with the gas-charged channels. Comparison of the imaged result to the legacy data shows significant improvement in imaging over the gas zone with the converted wave data. The result is important for evaluation of the remaining exploration potential in the area and could also be useful in seismic reservoir characterization for field development. Constraining the velocity model building and imaging in the most efficient way to benefit the data-driven process is the main goal of this study.
Journal of Geosciences and Geomatics. 2018, 6(3), 165-170. DOI: 10.12691/jgg-6-3-7
Pub. Date: December 12, 2018
7351 Views587 Downloads
by ALABI A. A. and ABDULLAHI S.
Original Research
Gold mineralization in Nigeria is traversed by regional northwest - southeast lineaments or shear zone which have been considered as continental extension of oceanic transform fault - fracture zone, and it is suggested that the migmatization and metamorphic deformation of the metasedimentary and metavolcanic rocks gave rise to dispersion of gold in quartz veins within the Nigeria basement complex. Combined geophysical methods have been used in the exploration for ore mineral bodies. Induced polarization (IP) technique has proved favourable for mineral exploration in hard rock terrain, as well as for ground water exploration and environmental geology studies. Also, magnetic technique has been used in identifying massive sulfide hosted quartz veins. The study area lies within the Kushaka schist Formation of the north-western block of Nigeria basement complex and Nigeria metallogeny province, the formation has been intruded by large volumes of granitic rocks that led to extensive migmatization of metasedimentary and metavolcanic rocks carrying substantial gold mineralization. Combined magnetic and IP and resistivity imaging technique was used in the study. The magnetic profiles in the study area showed anomalies of varying amplitudes. The variation in amplitudes of the residual intensity may be due to the presence of geological structures such as faults, dykes and contacts in the area. The total magnetic intensity map of the area exhibits zonation and alteration that indicates hydrothermal alteration which is usually associated with mineralization probably as a result of intrusion. Observed apparent resistivity and IP data presented as pseudo-section and 2-D inverted resistivity-IP mode show a qualitative idea of resistivity and chargeability distribution in the subsurface. The ground magnetic survey generally suggests a step or an edge structures like dyke or intrusion, such structures are of interest may hold mineralization at certain depth.
Journal of Geosciences and Geomatics. 2018, 6(3), 153-164. DOI: 10.12691/jgg-6-3-6
Pub. Date: December 04, 2018
12099 Views1439 Downloads
by ALABI Adekola Amos, GARBA Ibrahim, DANBATTA Umar Adamu and NAJIME Tavershima
Original Research
Bida basin is one of the younger sedimentary basins of Africa (Campanian – Maastrichitian) in Nigeria regarded as the northwestern extension of Anambra basin bounded by monotonous Precambrian basement rocks. Marine incursion in to the basin was suspected to have taken place during the early part of the uppermost Maastrichtian phase from the south via the Anambra basin, during which very extensive Sandstones and thick Kaolinite beds of the Patti Formation in the southern Bida basin were deposited. Stratigraphically, Bida basin is divided into the southern and northern parts. A topographic base map on a scale of 1:200,000 was generated for the study. Geochemical characterizations of thirty clay samples were analyzed for major, minor and trace elements. Field mapping revealed seven clay occurrences on isolated hills, floodplain and plain. Clays in the basin have high light REE/heavy REE ratio, negative Eu anomaly and Plot of Cr versus V suggest felsic source rocks. U/Th, V/Cr ratios and authigenic uranium values of the clays suggest an oxic environment of deposition in flood plain, alluvial fan and braided channel at the upper Maastrichian age that represent Upper cretaceous period.
Journal of Geosciences and Geomatics. 2018, 6(3), 147-152. DOI: 10.12691/jgg-6-3-5
Pub. Date: December 04, 2018
10077 Views1745 Downloads
by R.B. Ngatcha, O.A. Okunlola, C.E. Suh, E.R. Eben Mboe and C. Fuanya
Original Research
Geophysical, structural and geochemical data have been used to study the relationships between magmatism, tectonics, fluid circulation and gold mineralization in eastern Cameroon, and to provide pressure-temperature-composition-time paths constrained by the available dating. Primary gold mineralization displays spatial and temporal relationship with felsic to intermediate I-type granitoids emplaced in the 620-635 Ma period, in a volcanic arc setting at 625°C to 775°C. These granitoids were probably generated by partial melting of hydrated lower mafic crustal rocks, under oxidizing to moderately reduced conditions, where global permeability and tectonic regime allowed vertical fluid exchanges to be established. Mantle-derived, gold-enriched alkalic magmas are postulated as the ultimate source of gold enrichment in the crust. The Pan-African orogeny, and associated regional metamorphism and magmatism, generated large-scale movements of gold- and base metal-bearing fluids in the crust, channelized along complex fractures into regional NE-trending shear zones in Cameroon (e.g. Central Cameroon Shear Zone). However, these gold-rich alkalic magmas are so modified by crustal processes that evidence of their genetic relationship with gold become obscured. The primary ore mineral assemblage of quartz veins and veinlets within these shear zones consists of pyrite, galena, chalcopyrite, specular haematite, and gold. Preliminary fluid inclusion data from these auriferous quartz vein indicate that gold was probably transported predominantly as a bisulfide (HS¯) complex and deposited from low salinity (<1 to 8 wt% eq. NaCl) H2O–CO2(±CH4±N2) fluids that have total homogenization temperatures of 245-355°C. Desulfidation of hydrothermal fluids by Fe-bearing minerals in the wall-rock triggered the main gold precipitation phase. The major and trace element composition of ore-forming fluids from the mineralized vein, barren and granitic intrusion is still largely unknown, yet could provide important and more direct evidence for the fluid source(s). This is vital in establishing a direct genetic link between granitoids and gold mineralization.
Journal of Geosciences and Geomatics. 2018, 6(3), 138-146. DOI: 10.12691/jgg-6-3-4
Pub. Date: November 05, 2018
10708 Views2246 Downloads
by P. Azinwi Tamfuh, E. Temgoua, V.L. Onana, P. Wotchoko, F.O. Tabi and D. Bitom
Literature Review
Vertisols are tropical soils that occur world-wide (335 million ha) with high agricultural and other engineering potentials. However, they are underutilized as most of their physical characteristics make management techniques difficult and highly localized. This paper aims to highlight the characteristics, genesis and management strategies of Vertisols for sustainable use. Two main types of Vertisols can be distinguished: topomorphic Vertisols with A(B)gC or difficult A(B)Cg profile and lithomorphic with A(B)C profile type. Vertisols generally show a dark colour, very high compacity, surficial desiccation cracks when dry, surface ponding when moist and large sub-surface slickensides. They contain at least 30% clay fraction, while smectite, cation exchange capacity and base saturation are very high. Lithomorphic Vertisols are developed on various parent rocks and topographic positions where weathering generates base-rich environments that promote smectite synthesis. The formation of topomorphic Vertisols is favoured by low landscape positions suitable for accumulation of basic cations. The latter cover very extensive surface areas of the globe mainly in tropical, semi-arid to (sub) humid and Mediterranean climates showing contrasting wet and dry seasons, while the former have limited geographical extensions and occur mainly in specific islands and volcanic regions. Swelling and shrinking upon wetting and drying is a major characteristic of Vertisols. Most of their properties and uses are dependent on shrink-swell behaviour. Micromorphologically, plasmic separations occur in all Vertisols especially in the middle part of the profile where shrink/swell is most pronounced. Most Vertisols fall under the A-7-5 and A-7-6 classes typical of inorganic clays of medium to very high plasticity designated as bad clays according to AASHTO. Vertisols present numerous interesting uses in the chemical industry, pharmaceutics, agronomy and environmental protection. Nevertheless, man-made structures on Vertisols are not advisable since large investments are needed to maintain and repair damaged infrastructure. In North Cameroon, vertisols cover about 1 200 000 hectares and agricultural management strategies are mainly tilted at moisture control, but also at fertility restoration.
Journal of Geosciences and Geomatics. 2018, 6(3), 124-137. DOI: 10.12691/jgg-6-3-3
Pub. Date: October 24, 2018
12400 Views1998 Downloads3 Likes
by Hairie Ilkham Sibaruddin, Helmi Zulhaidi Mohd Shafri, Biswajeet Pradhan and Nuzul Azam Haron
Original Research
In this study, the capability of Unmanned Aerial Vehicle (UAV) optical data to provide reliable topographic and as-built information was tested using the eBee Sensefly UAV system. The Object-based Image Analysis (OBIA) technique was used to extract important geospatial information for mapping. The robust Taguchi method was adopted to optimise the segmentation process. Feature space optimisation method was used to obtain the best features for image classification utilising different supervised OBIA classifiers, such as K-nearest neighbour (KNN), normal Bayes (NB), decision tree (DT), random forest (RF) and support vector machine (SVM). Results showed that SVM obtained the highest percentage of overall accuracy, followed by RF, NB, DT and KNN at 97.20%, 95.80%, 93.14%, 86.01% and 77.62%, respectively. The McNemar test was implemented to analyse the significance of the classifier results. The as-built information showed that dimensional accuracy was less than 1 metre compared with ground survey measurement. We conclude that the combination of UAV and OBIA provides a rapid and efficient approach for map updating. This technique could replace the current procedure that utilises piloted aircraft and satellite images for data acquisition and reduce the time for digitising each feature that represents land cover for urban mapping.
Journal of Geosciences and Geomatics. 2018, 6(3), 103-123. DOI: 10.12691/jgg-6-3-2
Pub. Date: October 07, 2018
27286 Views1789 Downloads
by Milan Stafford Tchouatcha, Arnaud Patrice Kouske, Evine Laure Tanko Njiosseu, Paul Aubin Ngouem, Timoleon Ngnotue, Divine Ngong Njinchuki and Jean Paul Nzenti
Original Research
The ortho- and paraderived metamorphic formations of the Yaoundé series belong to the southern domain of the North Equatorial Pan-African Fold Belt. Para-derived formations of granulitic facies, which, unlike the other granulitic domains in the world, still contain preserved sedimentary features. These include the lithological banding which constitutes intercalation of garnet and kyanite-rich gneisses and quartzites, sometimes bedded, this banding of sedimentary origin is accentuated by the D1 tangential deformation which transposes the S0 bedding into foliation; the P1 intrafolial folds with horizontal fold axis and parallel to the bedding; lenticular structures marked by horizontal quartzite veins or boudins parallel to S0/S1 or S0/S1/S2 foliations, intercalated between the garnet and kyanite-rich gneisses, and sometimes lenses of garnet and kyanite-rich gneisses intercalated between the quartzites. They are either syn-D1 (quartzite or banded quartzite) sometimes transposing S0 stratification, or syn-D2 (quartzite, garnet-rich quartzite, granitic leucosome) linked to the in-situ partial melting of the garnet and kyanite-rich gneisses. The post-metamorphic and recent rock splitting, in contact with banded quartzite, quartzitic gneiss and other gneiss types, reflects an original pile of sedimentary formations of varied composition. The brittle (competent) behaviour of quartzite compared to the garnet and kyanite-rich gneisses which is rather ductile suggests the original pelitic nature for the garnet and kyanite-rich gneisses and sandstone for quartzites.
Journal of Geosciences and Geomatics. 2018, 6(3), 94-102. DOI: 10.12691/jgg-6-3-1
Pub. Date: September 05, 2018
9617 Views2075 Downloads