Abstract
Sian Goldfields Limited (SGL) recently re-examined its concession by integrating data in a GIS environment for the improvement of the mapping of the local geology as well as for delineating potential gold targets. Data employed included geochemical, topographic, geological and aerial photographic information. The geochemical data included 5660 soil samples collected over a terrain underlain by six different lithologies namely, rhyolites, greenstones, sheared greenstones, phyllites, sandstones and granites. The various lithologies and their boundaries were obtained from the shaded relief map derived from the topographic information whilst “ground truthing” confirmed and established the other geological contacts. The updated geology map generated from the geosciences data was superimposed on the soil gold geochemical plot. The integration of these datasets in the form of maps resulted in the easy definition of anomalous gold targets. The targets were delineated using background and threshold values of 30 ppb and 50 ppb respectively. The integration model approach portrayed many of the geological boundaries to have relations with mineralization. The use of the MapInfo-Discover GIS markedly aided to ascertain the geological contacts in areas where outcrops were uncommon. The re-analysis of the remote-sensed data and the ground truthing showed the clear contact between the Birimian system and the Voltaian units at the north eastern side of the concession. The integration of this information with soil geochemical gold results highlighted the most prospective gold targets. It is recommended that the granite-sheared greenstones/sheared greenstone-massive greenstones contacts and areas with defined soil anomalies should be subjected to further exploration works.
Highlights
Soil geochemical survey has widely been used as first phase exploration tool for gold (Au) in tropical rainforest regions where soils are considered residual in character
This study demonstrates Geographical Information Systems (GIS)-based predictive spatial analysis technique used to integrate multiple exploration datasets and map displaying favourability for the occurrence of the mineral deposit
The integration model approach portrayed many of the geological boundaries to have relations with mineralization
Summary
Soil geochemical survey has widely been used as first phase exploration tool for gold (Au) in tropical rainforest regions where soils are considered residual in character. Despite the residual characteristics of soils in these areas there are numerous associated exploration problems. Some of the problems are naturally low gold concentrations in some regolith materials, especially the depositional and lateritized environments. This renders uneven distribution of gold in surface samples as the landforms are not uniform creating isolated high and subtle gold assay values in soil anomalies that are not representative samples for areas analyzed. The continuous modifications of landscape results in both nugget effects and sample dilution that create a random phenomenon that masks the true geochemical signal.
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