Abstract:
A detailed geophysical survey was carried out at Babbantsauni and Ledi.A regional geological reconnaissance investigation was carried out by McConnell (1949) and identified that Izom Lead/Zinc is the only known considerate Lead/Zinc deposit in Nigeria outside the area covered by cretaceous rocks. The lodes appear to trend in the same direction. He also identified two types of veins (a) veins of hard grassy quartz with pyrite, galena and magnetite in small quantities (b) vein of shattered limonitic quartz containing irregular lenses and bodies of galena which are found in the cretaceous rock of Nigeria.The present investigations aim at targeting the veins of type (b) and delineate areas of the target veins and map out extent of mineralization.The area of investigation is located on Paiko SE Sheet 185SE and Abuja SW Sheet 186SW topographic maps.Babbantsauni site lies between Latitude 09o05’63” and 09o09’70” and Longitude 06o56’52” and 06o57’34”.Ledi site lies between Latitude 09o07’53”and 09o08’34”and Longitude 06o54’00”and 07o00’15”. The area is situated in Gwagwalada Local Government area of Federal Capital Territory, Abuja.The area is underlined by Basement rock, mainly Migmatite and low grade Schist belt. The main structural features in the area include the general North-South (N-S) and North East-South West (NE-SW) trending formation.The meandering stream pattern in the survey area is dendritic.The field work commenced on the 11th September, 2006 during the rainy season and ended on 12th November, 2006.Very Low Frequency Electromagnetic method (VLF-EM) method was adopted for carrying out the survey using SCINTREX ENV-VLF unit.Twenty-one (21) traverses of two kilometer length each was run in Babbantsauni and fourteen(14) in Ledi at a whole circle bearing of 315o which is perpendicular to anomaly strike direction.The geophysical data acquisition involved the use of three methods namelya. Electromagnetic method (VLF-EM), using SCINTREX ENVI-VLF unit.b. Electrical resistivity method using ABEM TEREMETER model SAS 300B.c. Gravity method, using WOODEN GRAVIMETER to corroborate VLF-EM result.MAGELLAN eXplorist ® 210 global positioning system (GPS) was used to determine each station position occupied by each method.Two techniques were adopted for processing namelya. Data enhancement techniques (for improve resolution)· Data transformations using the following soft wares.-Filter operator Fraser was used for filtering- Harous-Hjeit soft ware for model-WinGLink integrated Geosystem soft ware for applying various form of filters.-W-GeoSoft/Winsev 5.1 for plotting and modeling of VES data and plotting of resitivity curves.b. Data reduction· Reduction was applied to gravity data using mathematical formulae in MS Excel spread sheet· Using WinGLink for filtering of Gravity data.A double plot of the real and filtered real anomaly curves using Harous-Hjelt filter, highlight the conductive target. The conductive target are located beneath the point were cross over of the real anomaly coincides with positive peak of the filtered real anomaly.About on hundred and nine (109) such target points are identified with location in Babbantsauni and thirty-four (34) in Ledi within an area of 4 KmSq on both sides. Most of anomaly trend NE-SW others trending NW-SE direction and the range of the width of anomaly are between 10m to 130m with highest point located on TR13 with UTM location point 281648.190/1009922.725 (Northing/Easting ).On comparing gravity reduction plot with those of VLF-EM, the high gravity peak response corresponds to filtered real high peak response which is an indication of heavy metallic mineral.The area is highly mineralized and of economic significance. We recommence that pitting should be carried out in two conductive location to confirm the corroboration of VLF-EM/Gravity result in the following location,· In Babbantsauni the positions In UTM (northing easting) values are as follows§ 275299.632 , 1012130.808§ 275419.915 , 1012015.809· In Ledi§ 281648.190 , 1009922.725§ 281566.173, 1010079.265.
