An airborne gamma-ray spectrometer survey covering 2750 km2 in the Jabal Sayid area, Kingdom of Saudi Arabia, was flown to measure anomalous concentrations of potassium in a known mineral belt. No anomalies were detected over the Jabal Sayid copper prospect, although part of the prospect is within a radioactive, high-dispersion halo associated with the Jabal Sayid granitic pluton. Anomalous potassium concentrations were detected in several areas north of the mine at Mand adh Dhahab and over the rhyolitic rocks of the mine itself. Count-rate ratios of the potassium (K40), uranium (Bi214) and thorium (Tl208 ), reached a high of 24:1 for K:Th, and 11.6:1 for K:U. Count-rate ratios over granitic rocks are generally much lower. Areas of anomalous potassium correlate with rhyolitic rocks in some places. Other potassium anomalies have no known explanation, but may reflect unmapped potassium-rich rocks and(or) zones of hydrothermal alteration. These anomalies are considered as potential targets for further exploration, but ground follow-up investigations will be necessary to ascertain the exact cause of the anomalies.
