Rare element mineralization related to Precambrian alkali granites in the Arabian Shield

Saudi Arabian Dir.-Gen. Miner. Resour., Jeddah, Saudi Arabia

Five examples of disseminated rare element mineralization with sufficient resource potential to warrant exploration. All are characterized by enrichment in a suite of granitophile elements, which typically includes Nb, Ta, Sn, rare earth elements, Y, Th, U, and Zr, but they differ in size, geometry, mode of occurrence, and lithology. Two types of mineralization: the Jabal Sa'id type is characterized by high total iron to total alkali ratios and high K ₂ O/Na ₂ O ratios; the Ghurayyah type, is characterized by major oxide abundances approximating those of typical alkali granites. Both types evolved from alkali granite magmas formed by high-temperature, dry melting of late Proterozoic island-arc crust. Indicated resources range from 6 million metric tons (Jabal Tawlah and Umm al Birak) through + or -20 million metric tons (Jabal Sa'id and Jabal Hamra') to 440 million metric tons (Ghurayyah). The highest average grades from Nb (3,400 ppm), Sn (380 ppm), Y (5,200 ppm), and Zr (37,000 ppm) occur at Jabal Tawlah; the highest Ta grades (200 ppm) at Ghurayyah; and the highest U (130 ppm) and Th (830 ppm) grades at Jabal Sa'id.--Modified journal abstract.

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