Application of Integrated Geophysical Methods for Graphite Exploration in Gara-Gedemsa Area (Moy Ale, Southern Ethiopia

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Addis Abeba university


The thesis research was aimed at stud)ing the theoretical and practical aspects of the Radiometric, 'vIagnetic, Electromagnetic, Induced Polarization (IP) and Resistivity methods and apply the integrated methods for graphite exploration in the Gara Gedemsa area. TIle physical plinciples and mathematical foundations, fields of applications and Plinciples of data acquisition and interpretation of each method are studied in detail. Integrated geophysical survey, comprising the Radiometric, Magnetic, GENlE-EM, IP and Resistivity methods, was conducted in the Gara Gedemsa area to map the lateral and vertical distributions of the graphitic mineralization. The area is located in Southern Ethiopia some 6 km northlv<;:st of ;Vloyale to\Yn. Geologically, tllis area is mostly covered by mafic-ultramafic rocks (talc-tremolite. talc-tremolite-actinolite and ampllibole schists), whereas quartzite, quartz-utica sellist and pegmatite veins that are closely distributed \\1th the graphite scllists are found to have rebtive1y smaller di,tribution. The geophysical survey results have delineated one major grapltitic zone at the southern margin of th" survey gJld with shike length more than 2 km along W30~ and an average 1\ idth \'arying from 25m to 50 m. From the pole-dipole IP, Resislh lty and GENlE amplitude ratio data. tlus gJ'aphitic body is found to be dipping towards not1h at about 55° and extends to a depth of not kss than 50 m. TIus grapltitic zone is almost equally demarcated by ,Ill methods employed for lh~ SUl'\"~'. HO\\ever. the GE:-"1E-E:\I survey with the 50 III transnlitler-receiver spacing has shOI\n better resolution in di~criminaling the paralld gJ'aplulic lenses closely separated by the nonconducth'e quartz-utica schists . .-\ less prominent gJ'apltitic zone is outlined at the central part of the gJid, and from exploration point of view, it deserves less interest due to its smaller lateral distlibution and low anomaly-to-backgJ'ound contrast. Based on the geophysical survey results, a generahled physicogeological model of the Gara Gedemsa gJ'apllite OCCUITence is generated. Moreover, two bore holes are recommended over the main gJ'apllitic zone in order to corul!:m its depth extension and then:by evaluate the econoutic significance of the deposit



Graphite Exploration