“An update of the geology of the South Eastern portion of the Ashanti Goldfields Company Limited (A. G. C.) concession at Obuasi, using airborne geophysical data”
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Date
2001-12-13
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Abstract
High-resolution airborne geophysical surveys have become fundamental and indispensable tools as far as an integrated approach to modern geological mapping is concerned. They became even vital in the tropics where rock exposures are not always available, in which case conventional geological prospecting, cannot predict the trend of ore formation with reasonable certainty. Thus, Ashanti Goldflelds Company (A. G. C.) Limited, a leading gold mining company based in Ghana, contracted Aerodat Incorporated of Canada, to undertake an airborne geophysical survey to reveal the areas or trends of potential mineralization as well as the lithologies on their property. A helicopter borne magnetic and electromagnetic surveys was conducted over the concession. A fixed wing exclusive geophysical survey had been conducted over the southwestern part of Ghana prior to the helicopter survey and the radiometric data covering the concession was made available to the company. Although much exploration has been done in the southeastern portion of the consolidated concession of A. G. C., it has been by the conventional method of looking for rock exposures.
The aeromagnetic survey was useful in providing information on the broad geology. It clearly distinguished between the Upper Birimian and the Tarkwaian in the study area. Magnetic highs were observed more over the Tarkwaian than the Upper Birimian. The magnetics, however, could not define the lithological units within the study area. A fault was observed in the study area from the analytic signal image.
The EM survey, from which apparent resistivities and effective depths were calculated, also distinguished between the Upper Birimian and the Tarkwaian in that the Tarkwaian was more resistive. The Kawere group with its associated conglomerates was found to be conductive due to the fluvial association. Together with the radiometrics however, there was some clear lithological distinction between the metavolcanics, conglomerates and the quartzite on the A. G. C. property.
Description
A thesis report submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements of the Master of Science Degree in Mineral Exploration, 2001