Geology and ore deposits of the Kutam Mine, Kingdom of Saudi Arabia

Abstract

The ancient Kutam mine in southwestern Saudi Arabia was discovered during the course of regional geologic mapping. Malachite coatings along fractures in the ancient workings and nearby large piles of slag indicate the mine was worked for copper. Quartz porphyry of Precambrian age is the principal host rock of the deposit. The quartz porphyry is associated with volcanic rocks of mafic to intermediate composition. All rocks have been deformed and metamorphosed to various types of schist, of which quartz-sericite-chlorite schist is the most common. Mineralization is thought to be controlled by the convergence of three fault patterns that strike N 60°W., N 45°W and N. 20°W, respectively, and dip steeply west to vertical. Cross faults that extend between faults of the N 45°W. pattern have influenced deposition of sulfides locally. Southeast-plunging lineation derived from two converging directions of planar schistosity also may have exerted control on sulfide deposition. Detailed geologic mapping of surface features and geochemical and geophysical studies indicated that the deposit warranted subsurface exploration. Accordingly, eight holes were drilled that delineated possible economic-grade sulfide deposits in an area about 300 m long and which is known to continue to a depth of more than 200 m. However, drilling found copper-zinc mineralization along a strike length of 850 m. Drill findings show that copper and zinc sulfides partially replace chlorite and higher concentrations of chlorite generally define the higher-grade mineralization. The more intensely chloritized zones tend to follow the N.45°W. fracture pattern. South of drill hole KA-I, the sulfide mineralization may plunge 40° to 60° southeast. Indicated and inferred reserves outlined by drilling total 8,056,000 metric tons, the grade of which averages 0.31 g/t Au, 6.13 g/t Ag, 1.83 percent Cu, and 0.95 percent Zn.