“AREA-SELECTION” USING GIS AND MINERAL EXPLORATION MODELING

The Precambrian Shield of Saudi Arabia covers more than 680,000 km2 of the western Arabian Peninsula, encompassing about a third of the Kingdom of Saudi Arabia. More than 2100 metal occurrences are known from the Shield, 138 of which contain significant resources. The distributions of Au, Ag, Pb, Zn, Cu, Mo, Sn, W, Cr, Ni, Fe, and Mn were used as “skeletons” upon which to examine spatial relationships between metal locations and data in a Geographic Information System (GIS). Data layers include topography, rock types, rock ages, lineaments, lithotectonic terranes, and regional gravity and magnetism. “Guide” tables that summarize the distributions of metals with respect to the data layers were established for each metal – seven tables per metal. The tables were used as input for two exploration models: an Index Overlay Model with Binary Evidence Maps (IOM-BEM), and a Binary Logic Model (BLM). For the IOM-BEM model, pixels from each input data layer were classified either as zero (no exploration potential) or one (favorable potential). The favorable pixels were re-classified into seven categories, the upper one representing high exploration potential. The BLM model uses the same input pixels (zero or one), but pixels in the resulting map are considered favorable only if all seven of the input layers contain favorable information for a location. Areas that are highlighted by the BLM model are smaller, but they probably are the most reliable in an exploration sense. The exploration models “select” areas for follow-up study. The IOM-BEM model for gold identified 11,903 km2 of high potential rocks in the ArRayn terrane and the Zalm sub-terrane of the Afif terrane (1.74% of the Shield). This number was reduced by the BLM model to 6691 km2 (0.98% of Shield). The numbers for copper are, for the IOM-BEM model, 8397 km2 (1.23%), and the BLM, 4153 km2 (0.61%), all within the Zalm sub-terrane of the Afif terrane.