Application of Geographic Information System for Mineral Exploration in Nigeria

Application of Geographic Information System for Mineral Exploration in Nigeria Irmiya S. Amoka and Shadrach B. Jatau Mineral Resources Engineering Department, Kaduna Polytechnic, Kaduna, Nigeria,
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Application of Geographic Information System for Mineral Exploration in Nigeria Irmiya S. Amoka and Shadrach B. Jatau Mineral Resources Engineering Department, Kaduna Polytechnic, Kaduna, Nigeria, Abstract. Delineation and evaluation of mineral resources are major exploration parameters required for investment decisions. In Nigeria, however, there is acute shortage of such data to ensure rapid mineral development. Recent integration of exploration data with GIS, supported by intelligent systems, has greatly enhanced the acquisition, analysis and interpretation of complex problems of probabilities and decisions involved in mineral projects. Geophysical studies and mineral reserves estimation have been undertaken to illustrate major areas of GIS application in Nigeria s mineral industry. Resistivity profiles from Ungwar-Doka and Rafin-Gabas, North-central part of Nigeria, were digitized into GIS to delineate tourmaline and chalcopyrite resources. Drill-hole data from Malori and Gurjaji in north-eastern Nigeria were used to generate isopach maps of gypsum quantities from which the reserves were calculated. The results demonstrate the potential of the GIS in speedy and reliable execution of mineral exploration projects. Keywords: GIS; mineral exploration, geophysical survey, tourmaline, reserves estimation, gypsum 1 Introduction Nigeria is endowed with numerous minerals but they are grossly underdeveloped. This has been mainly attributed to the shortage of accurate and reliable data base with respect to the location, quantity, and spatial characteristics of ore deposits. Such data are produced at the mineral exploration stage, and are necessary for feasibility, planning and production decisions. The required geological, geophysical, geographical, geochemical and geotechnical investigations often generate large volumes of data, and complex analysis and decisions are involved. The need for computerization is therefore inevitable. The variability of geological features and factors, in space and time, had led to various attempts to solve complicated geological problems using multivariate and geostatistical methods [1]. This eventually resulted in the development of specialized mining packages in the late 70s and 80s, for geological data analysis, from simple data interpolation/ extrapolation to 3-D visualization. However, the costs of the packages were prohibitive, and thus were not easily accessible to the general geological community. Geographical Information System (GIS), which was essentially developed for the geographical community [1] has, therefore, become attractive to the minerals industry because of its recent advancements involving the incorporation of multivariate, geostatistical modules and powerful 3-D analysis. The more recent applications of GIS integrate intelligent 361 systems to enhance its capabilities for complex modelling, simulation and predictive decisions often encountered in mineral exploration and exploitation [2,3,4]. 2 Geographical Information Systems A geographic information system integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information [4,5]. The GIS can be viewed in three ways: Database, Map, and Model Views. Together, these critical parts of an intelligent GIS are used at varying levels in all GIS applications. Major areas of application in minerals exploration and mining include geological and mineral potential mapping [6,7,8,9], geophysical exploration modelling [10], mineral resources inventory and evaluation [3,11,12], and mine environmental monitoring [13]. The use of GIS in underground mining for optimization has been cited, with reference to four technical areas: land ownership and mineral claims, exploration management, production, and mine safety [14]. In Nigeria, several forums are presently directed towards promoting the use of GIS, particularly for land surveying and environmental monitoring. The GIS has been used as a tool for managing electricity distribution network [15] and crime mapping and management [16]. In the area of mineral exploration, a GIS database of the mineral resources of Igarra, south-western Nigeria was utilized to carry out a digital update of the existing geological map [8]. This is expected to contribute accurate and up-to-date metadata to Nigeria s National Geospatial Data Infrastructure (NGDI) which is at its formative stage. The GIS has also been used to display, analyze and model topographic and lithologic data from Nigeria SAT-1 with respect to wolfromite and cassiterite mineralization in Rafin-Gabas, north-central Nigeria [9]. The present paper illustrates the use of GIS in two major areas of mineral exploration, with particular reference to geophysical delineation of tourmaline and chalcopyrite deposits in north-central Nigeria, and for reserves estimation of gypsum deposits in Malori Gurjaji area of the north-east. 362 3 GIS in Geophysical Surveys Electrical resistivity data were integrated with GIS to delineate a tourmaline deposit in Ungwar-Doka [17], and chalcopyrite in Rafin-Gabas [18], both in Kokona area, northcentral Nigeria (Fig. 1). Using ABEM Terrameter SAS 300c, Wenner array points were taken on a quartz-vein along 3 profiles, 100m apart. The GIS software was used to convert the field data to 7 iso-resistivity maps at depths of 5m, 10m, 15m, 20m, 25m, 30m and 40m. The field data were first organized into a Microsoft Excel spread sheet and saved as a data base file. The data were then used as input into the GIS software. Figure 2 shows an example of iso-resistivity contour maps for tourmaline deposit at Ungwar-Doka, while Figure 3 shows that of chalcopyrite deposit at Rafin-Gabas. The isoresistivity contours were produced by grouping the data within a range of 100Ωm interval, to produce the different contour lines for each map. The contour lines were differentiated by various colours. GPS coordinates were used to fix a grid system on the maps. The iso-resistivity maps indicated the probable occurrence of tourmaline between 10m and 40m, with very prominent occurrence at a depth of 40m. The probable occurrence of chalcopyrite deposit was also indicated from the depth of 5m down to 40m. At both locations, however, core drilling would be necessary for ore reserve estimation to ascertain the economic viability of the deposits. 363 364 4 GIS in Mineral Reserves Estimation A mineral reserve is that part of a mineral resource that meets minimum physical and chemical criteria, related specific mining and processing methods and can be reasonably assumed to be economically and legally mined or produced at the time of the determination [19]. Reserves of two gypsum deposits were estimated using GIS, with data from 25 boreholes in two areas of north-eastern Nigeria, 18 in Malori and 7 in Gurjaji [20]. Coordinates of all the boreholes were obtained using a GPS at the drilled points. By digitizing the exploration data into the GIS software, contour slicing maps were produced for both top and beneath surfaces of the study areas covering 1,010,316m 2 at Malori and 306,111m 2 at Gurjaji (Figures 6 8). The contour maps were analyzed to calculate the mineral reserves. The surface analysis showed that the gypsum volumes for Malori and Gurjaji were 12,815,721m 3 and 3,030,376m 3 respectively. The estimated reserves were 29,476,159 tonnes and 6,969,865 tonnes respectively. The reserves obtained by the GIS method compared closely with those determined by the conventional triangular method. 365 366 367 5 Conclusion It has been demonstrated that GIS can provide a very speedy and reliable tool for geological mapping, geophysical survey and interpretation, as well as mineral reserve estimation of different mineralizations in Nigeria. Its popularity and fuller adoption would be enhanced when the mineral industry is revitalised. It is envisaged that the incorporation of intelligent systems in GIS would particularly stimulate the application and realization of the simulation, modelling and investment decisions capabilities for mineral exploration in Nigeria. Acknowledgements: The authors are grateful to Mr. Kolawole Ogunniyi for his generous assistance with the GIS software. References 1. Champati Ray, P.K.: GIS in Geoscience: The Recent Trends. Geospatial Application Papers, 2. Thurston, J.: GIS & Artificial Neural Networks: Does Your GIS Think? (2002) 3. Mukhopadhyay, B. Saha, A., Hazra, N.: Knowledge Driven GIS Modelling Techniques for Copper Prospectivity Mapping in Singhbhum Copper Belt - A Retrospection, Map India (2003) 4. ESRI: What is GIS? the Guide to Geographic Information Systems 5. Escobar, F., Hunter, G., Bishop, I., Zerger, A.: Introduction to GIS. (2010) 6. Tew, B.H., Osborne, W.E.: Digital Geologic Mapping Program at the Geological Survey of Alabama, U.S. Geologic Survey Open-File Report (1997) 7. Rahimi, M. GIS in Exploration with Special Viewpoint to Mineral Potential and Defining the Exploration Priority Maps. Map India (2002) 8. Establishing a Solid Mineral Database for a Part of South-Western Nigeria. Mineral & Mining, Map Africa (2006) 9. Anifowose, A.Y.B., Bamisaye, O.A., Odeyemi, I.B.: Establishing a Solid Mineral Database for a Part of South-western Nigeria. Geospatial Application Papers, Map Africa (2006) 10. Bhasin, P.: Mineral Exploration - Using Modern Techniques. Geospatial Application Papers, 11. Ayachi, A.K.: Advance Mineral Resources Information System (M.R.I.S v 2.0) Using Remote Sensing and GIS Inputs. Map Asia (2003) 12. Gojamanov, M.H., Arafat, A.A.: Creating Data Base for Iron Ore Reserves Evaluation in Egypt by Utilizing GIS Technology. (2009) 13. Dobson, J.E., Durfee, R.C.: ORNL and the geographic information systems revolution Kumar, L, Viswakarma, J.K., Singh, V.: Use of GIS in Underground Mining for Optimization. Abstract, Map World Forum (2007) 368 15. Igbokwe, J. I., Emengini, E. J.: GIS in Management of Electricity Distribution Network: A Case Study of Onitsha-North L.G.A., Anambra State, Nigeria. GIS Development Ezines, Geospatial Application Papers, 16. Fajemirokun, F., Adewale, O., Idowu, T., Oyewusi, A., Maiyegun, B.: A GIS Approach to Crime Mapping and Management in Nigeria: A Case Study of Victoria Island Lagos. TS47, GIS Applications, Special Issues: Shaping the Change, XXIII FIG Congress, (2006) 17. Badamasi, B.I.: Electrical Resistivity Delineation of Tourmaline Deposit at Angwan Doka, Kokona Local Government Area, Nasarawa State. HND Project Report, Kaduna Polytechnic (2009) 18. Eneanya, D.N. Electrical Resistivity Appraisal of Chalcopyrite Deposit at Rafin-Gabas, Kokona Local Government Area, Nasarawa State. HND Project Report, Kaduna Polytechnic (2009) 19. David, M.: Geostatistical Ore Reserve Estimation. New York: Elsevier Publications (1977) 20. Zakari, I.: Application of Geographic Information System and Triangular Methods for Gypsum Reserve Estimation at Malori and Gurjaji, North-Eastern Nigeria. HND Project Report, Kaduna Polytechnic, Kaduna (2009) 369 370
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