Assessment Of An Iron Formation Deposit In Ikanga Area, Kitui County, South Eastern Kenya
Bhollai, D. Lawrence
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This Research was conducted in the Ikanga area, which occurs at the intersection of longitude 38o33’50’’E and latitude 1.7o25’45’’ S in Kitui County, south-eastern Kenya. The Area lies within the Neoproterozoic Mozambique Belt in which the iron formation deposit, which is the main focus of this study occurs. The deposit is, approximately 250km away from the city of Nairobi. This study was conducted purposely to assess the iron formation deposit in the Ikanga area and find out whether it has some economic value or not. The area is a gently low undulating semi-arid land with acacia tree family and dry drainage system. The rock types of the area are Neoproterozoic in age and include granitoid gneisses which are dominant. On the local scale, granitoid, feldspathic gneisses, kunkar limestone, migmatite, lateritic-silica-baked-ferrous-canga and marble do occur. Alluvial sandy soil deposits of Pleistocene and Recent Age, which include red and black soils, form the local geology of the study area. In pursuance of this research, the following methods were applied: 1). Remote Sensing; 2). Ground Magnetic Survey; 3). Geochemical Analysis; 4). Mineralogical and Petrographical Analyses; and 5). Data Analysis using Software Applications. Application of these methods showed varied results. Remote sensing gave a broad pictorial view of the study area and its surroundings and identified where the iron formation deposit is concentrated for favorable sampling point sections prior to the field work. The Landsat Band etm+3:1 ratio for iron oxide displayed the dispersion of the iron formation in the study area. The ground magnetic method was able to determine the magnetic fields of the area. A proton precision magnetometer was employed in this geophysical mapping to collect total magnetic field in the area. Analysis of the total magnetic intensity (TMI) of the area and associated magnetic source results mark the locations and orientations of southwest-northeast trending linear structures at depth caused by shearing and subsequent mineral alterations. The areas occupied by magnetic highs to the east are interpreted to coincide with locations of iron formations and require ground follow-up and truthing. Geochemical data analyses confirmed predominantly oxide facies mineralization with Fe2O3 as the main iron oxide. The highest non-iron oxide amounts in the domain include TiO2 (≤9.72 wt% in the soil), MnO (≤ 0.2 wt% in haematite, gneiss, and soil), CaO (≤ 54.7 wt% in limestone), Al2O3 (≤ 21.8 wt% in soil), Na2O (≤ 4.31 wt% in gneiss), K2O (≤ 3.6 wt % in soil) and SiO2 (≤ 83.63 wt% in pegmatites). The Fe2O3 wt% in the hematite mineralized samples ranges from 72.4% to 86.3% Fe2O3 wt% with an average of 76.97 Fe2O3 wt%. In gneisses the Fe2O3 wt% ranges from 3.38 to 16.4 wt%, with an average of 8.0 wt%, while in the soil the Fe2O3 wt% ranges from 3.9 to 79.6 wt%, with an average of 22.65 wt%. The geochemical data indicate that the Ikanga deposit is very likely to have been derived from a Precambrian Banded Iron Formation (BIF) precursor by the weathering processes.