Integrated Geophysical Investigations for Gold in Dembi Dolo Zone, Western Ethiopia
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Date
2011-11
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Addis Ababa Universty
Abstract
This manuscript presents a Masters degree thesis dealing with an integrated,
IP/Resistivity and magnetic, surveys conducted as part of a systematic exploration
program to map the subsurface litho-structural features favourable for gold
mineralization in Gute Soyoma area, Dembi-Dolo zone, of western Ethiopia. The
geophysical surveys particularly aim at mapping the subsurface signatures of rock
units and structural controls responsible for the observed high gold values seen in
a systematic geochemical survey over selected targets.
Geologically, the study area is located in the western Ethiopia shield and covered
with basement rocks hosting economic metallic mineral deposits. It consists of
gneissic rocks and metasedimentary-metavolcanics assemblages (amphibolite to
greenschist facies). These rock assemblages host gold and other base metal
mineralizations.
Qualitative interpretation of the total field magnetic data along eight profiles
showed the presence of magnetic minerals and possible shear related structures,
which are litho-structural indications of gold mineralization. On the other hand,
appraisal of six traverse lines of IP/Resistivity data revealed that along most of the
survey lines, over the regions of high gold showings, high IP amplitudes (>25mV/V),
over a background of 1 – 5mV/V, were detected and very often, spatially associated
to zones very high resistivity (in excess of 2000Wm). These are interpreted to arise
from sulphide minerals in silicified zones, which are closely associated to the main
structural features such as shearing.
The current results of the integrated methods of IP/Resistivity and magnetic have
showed good correlations, reduced the ambiguity inherent of the geophysical data
interpretations, and highlights the sulphide minerals are disseminated type and
hosted by intuitively silicified rocks. These prominent geophysical anomalous zones
attributed to the mineralized zone have been shown to be open to the eastern and
southern border of the current detail area. Therefore, continuation along these
directions is highly recommended.
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Gold in Dembi Dolo Zone