Application of geographic information systems (GIS) in mineral exploration for the Arabian Shield of Saudi Arabia.

摘要

The Precambrian Shield of Saudi Arabia covers more than 680,000 km 2 of the western Arabian Peninsula, encompassing a third of Saudi Arabia. Rocks there are principally upper Proterozoic volcanics and volcanoclastics intruded by igneous plutons and dykes. More that 2,100 metallic mineral occurrences are known throughout the Shield, 138 of which have been shown to contain significant resources. This research extends the potential of known occurrences, and predicts where similar deposits may lie concealed. Data layers covering the Shield include lithofacies, lineaments, lithotectonic terranes, magnetics, topography, and gravity. Geographic boundaries, and roads and cities provide additional layers.; Occurrences of 12 metals (Ag, Au, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sn, W, Zn) were utilized as “skeletons” upon which to examine spatial relationship between mineral locations and the data in the GIS layers. Seven “guide” tables that summarize those relationships were established for each metal, and used to produce input grids for three exploration models: binary logic model (BLM), index overlay model with binary evidence maps (IOM-BEM), and index overlay model with multi-class maps (IOM-MCM).; The area of metal potential highlighted in the BLM exploration model is the smallest among the three models, but believably the most reliable. Because the BLM model utilizes Boolean AND (binary intersection), it has a tendency to minimize the size of the potential exploration areas, and it reduces by too much the chances of finding extensions of known metal deposits, or discovering new deposits. On the other hand, the area of potential in the IOM-MCM model is the largest, and probably the least reliable. This model has a tendency to enlarge the size of the potential exploration areas to unsupportable levels, especially in the areas of low to moderate potential, which might provide unrealistic expectations. The IOM-BEM model utilizes Boolean OR (binary union), and falls “between” the BLM and the IOM-MCM models in term of its reliability and the size of the area of metal potential it highlights. Evaluation of the three exploration models for each metal has led to a conclusion that the IOM-BEM model is the best predictor of exploration potential areas.