Ore Mineralization in Mutomo – Ikutha Area, SE Kenya
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Universal Journal of Geoscience 3(2): 39-50, 2015 http://www.hrpub.org DOI: 10.13189/ujg.2015.030201 Integration of Geological Mapping and Remote Sensed Studies for the Discovery of Iron – Ore Mineralization in Mutomo – Ikutha Area, SE Kenya Aaron K. Waswa1,*, Christopher M. Nyamai1, Eliud M. Mathu2, Daniel W. Ichang’i1 1Department of Geology, University of Nairobi, Kenya 2Department of Geological Sciences, SE Kenya University, Kenya Copyright © 2015 Horizon Research Publishing All rights reserved. Abstract This research integrates geology with remote Keywords Remote Sensing, Iron Ore, Neoproterozoic sensing techniques to establish characteristic features that can be used to discover iron ore mineralization within the Neoproterozoic rocks of Mutomo – Ikutha area in south eastern Kenya. The association of hornblende gneiss and shearing as well as alteration processes near the mineralized 1. Introduction regions appear to play an important role in the distribution and localization of the iron mineralization The methods used The study area is located between longitudes 38º 4´E to in this research include Image processing techniques applied 38º 20´E and latitudes 1º 48´S to 2º 8´S in South Kitui within on the digital subset ETM+ data that cover Mutomo – Ikutha the Kitui County occupying about 100 Km2 (Figure. 1). In area and geological field mapping. These techniques this paper, we show how we have used remote sensing and generated several products of enhanced satellite imagery, field based investigation to come up with a structural and a such as colour composite images, ratio images and principal mineral resource map. New geological structures discovered component images. These techniques have been successfully include shear zones and faults that control iron ore used in the lithological discrimination of iron ore bearing mineralization. Orientation analysis has revealed two shear sheared hornblende gneisses. The capabilities of remote zones associated with iron ore mineralization. The Tiva sensing data to characterize the iron ore bearing gneisses, in shear and Mutito shear trending in the NW-SE direction. addition to characterization and mapping the hydrothermal Another important discovery is the location of Mineral alteration zones helped in identification of iron mineralization regions. Extensive field geologic and deposits associated with alteration within the gneisses. geochemical investigations to the pronounced zones Although previous researchers had done geological mapping delineated by the image processing technique, led to and produced maps for Ikutha area, the structures, lithology discovery of four locations of high iron anomalies with some and mineral resources discovered were missing. This iron mineralization, mainly connected to the studied research attempts to answers some of the questions for the Neoproterozoic hornblende gneisses. Chemical studies were gaps left by the previous researchers. carried out using atomic absorption spectrophotometer (AAS) Image Processing techniques were applied in this work to and X-Ray florescence, for some selected mineralized define the main characteristic features of the gneisses samples. Petrographic analysis and physical properties of the rock-bearing iron mineralization. The enhanced thematic iron minerals were carried out as well. These investigations mapper plus (ETM+) digital data of Landsat 7 satellite was confirm the present iron mineral to be magnetite ore enriched used to recognize and map the investigated area. The with phosphates. The magnetite is found in close association constructed colour composite images and application of with apatite chalcopyrite, quartz, and chlorite. Relics of principal component analyses of ETM+ data led to identify corroded magnetite grains are occur along the Tiva river bed and characterize the iron ore -bearing gneisses in the as well as along the road sides. investigated area. 40 Integration of Geological Mapping and Remote Sensed Studies for the Discovery of Iron – Ore Mineralization in Mutomo – Ikutha Area, SE Kenya Figure 1. The map showing the area of the project. Major towns within the area include Mutomo and Ikutha. 2. Geology of the Study Area An attempt has been made here to update the geology of Mutomo – Ikutha area. This is to fill the gap left by the The Mozambique Belt is a major N-S trending previous geologists who missed out some of the geological metarmophic and lithotectonic domain that extends along the details that have been noted during the current survey. The Eastern Coast of Africa, as well as in Saudi Arabia, current survey has also managed to establish continuity of Madagascar, India and Sri Lanka. It was first defined by rock units from the area mapped by Saggerson [28] to the Holmes [1], mostly on metamorphic and structural criteria. area mapped by Walsh [29]. The rocks of the Mozambique The Mozambique is a Neoproterozoic Belt (900 to 550) mobile belt are considered to be the metamorphosed which was affected by the Pan African tectonothermal event about 650 Ma, as suggested by (Kennedy [2] ; equivalents of originally sedimentary rocks, the sedimentary Kazmin [3]; Kröner [4] ; Cartier [5]) who considered it as a pattern being retained. The repetition of certain beds, e.g. the major phase of division of the African continent linked to the meta-calcareous horizons in the area, the presence of development of mobile belts. The Pan African event originally carbonaceous limestone, and preserved current- encompasses a wide time span from 650 to 500 Million years. bedding and stratiform succession are considered proof of Mozambique Belt is considered as an orogen resulting from sedimentary origin. Evidence of lateral variation is observed the oblique collision between two Gondwana fragments, in this area. The pelitic gneisses grade into rocks which do [Muhongo [6] Burke and Derwey [7]; Gass [8]; Key et al. [9]; not contain the higher-grade index mineral. An example of Kröner [4]). Stern [10] proposed its name to be changed to lateral variation is seen south of Mutomo area where the East African Orogen. The fact that the collision was oblique biotite gneisses grade imperceptibly into biotite-hornblende resulted in the development of large shear zones parallel to gneisses. Another lateral variation is noted in Ikutha area the direction of the orogeny after the main collision phase, where biotite gneiss grades gradually into biotite hornblende owing to tectonic escape phenomena. The geology, and gneiss. structures, tectonic the history of the Mozambique Belt in An attempt has been made here to classify rock units of the Kenya has been reviewed, by (Mathu and Tole [11] 1984; area based on field relation, lithology and colour into groups Key et al. [9]; Mathu [12]; Mathu et al.[13]; Mathu et al.[14]; and formation. These groups include; Ikutha and Mutomo Gaciri et al.[15]; Biyajima et al.[16]; Suwa et al.[17] ; Opiyo groups. The formations and members of these groups have – Aketch and Nyambok, 1984; [18] Hackman et been subsequently discussed in the following sections. al.[19];Mosley [20]; Nyamai [21], and [22-27]. Universal Journal of Geoscience 3(2): 39-50, 2015 41 Table 1. Lithostratigraphy of Mutomo – Ikutha area SUPER GROUP GROUPS FORMATIONS MEMBERS Hornblende gneiss Quartzo-feldspathic gneiss Hornblende biotite gneiss TIVA GNEISSES Hornblende diopside gneisses Granitoid gneiss IKUTHA GROUP Amphibolites Migmatites Hornblende-biotite gneisses UKAMBA SUPER KASALA Hornblende-diopside gneisses GROUP GNEISSES Crystalline limestone Biotite gneisses MBEBETWA GNEISSES Migmatites Biotite-garnet gneisses MUTOMO GROUP Feldspar porphyroblast gneiss KAPOPONI GNEISSES Calc-silicate granulite Migmatites Quartzo feldspathic gneiss (a) (b) Figure 2: (a) Nzamba-Miusiani hill – A view taken from Ngotheni area in Ikutha area composed of high grade metamorphic rocks, (b) Mutomo hills, along Mutomo – Mutha road composed of high grade metamorphic rocks. 2.1. Iron Mineralization and Stratigraphic Setting of classified lithostratigraphically as above. Mutomo – Ikutha Segment in Mozambique Mobile Belt of SE Kenya 3. Image Processing of Remotely Sensed Mineralization in the study area is mainly controlled by Data the stratigraphy and structures. Stratigraphy of Mutomo – Ikutha area is largely classified on the basis of the lithology The remotely sensed raw data of the studied areas are of the rocks (Table 1). According to the regulation of the included in Landsat-7 Enhanced Thematic Mapper Plus international Subcomission on Stratigraphic Classification (ETM+) data scenes number 167/61 (Path/Row) covers [30] of the international Union of the Geological Sciences Mutomo – Ikutha area. Subsets of the digital ETM+ imagery (IUGS), the stratigraphy of Mutomo – Ikutha area is covering the studied areas were obtained. The image considered to be composed of lithostratigraphic rock units. processing techniques were applied in this work using ENVI In designing nomenclature of the rocks in the study area, the 4.8, ArcGIS 10 and PCI, GeoAnalyst software-package. North American Stratigraphic code prepared by the North Geometric correction has been done for the digital data of the American Commission on Stratigraphic Nomenclature, and ETM+ bands of the study areas. Raw digital satellite data the rules for naming geological units in Norway [31], have usually includes geometric distortions due to sensor been used. It involves a general description of the unit, origin geometry, scanner, platform instabilities, earth rotation, of its name