A Contribution to the Geochemical Atlas of the Kingdom of Saudi Arabia: Geochemical Survey of the Rabigh Quadrangle, 22D
Ibrahim O. Abdalla, Mohammed Al-Thekair, Ahmed H. Al-Johani, Yasir Al-Ghanmi, Mohammed Al-Nashri, Abdulrahman Sabbahi, Abdullah Al-Eisa, and Mazen Balkheyour
A reconnaissance stream-sediment survey carried out in the Rabigh quadrangle, north of the Jeddah-Makkah area, has resulted in the identification of four Priority 1 anomalies, six Priority 2 anomalies and nine Priority 3 anomalies. The survey comprised the collection of 525 samples (including 6% site duplicates) collected over Late Proterozoic granitic and supracrustal basement terrain in the west of the quadrangle, and Tertiary lava flows in the east, as well as Quaternary surficial deposits. The minus-2 millimeter / plus 0.177 millimeter fraction of the samples was subjected to analysis for 10 major and 29 trace elements by ICP-OES, and for 11 trace elements by AAS after HF/ HClO4/ HCl/ HNO3 digestion. The precision of the analyses, as measured by analysis of 30 site duplicates, varies from ±6% for SiO2 to ±178% at 95% confidence level for W, with the majority of elements falling between ±20% and ±40%. These results are considered to be adequate for the purpose of the current study. The anomalies were identified after detailed study of the distribution of individual elements. The Priority 1 anomalies comprise one over granitic/supracrustal terrain whose element associations (As, Cu and Zn) suggest hydrothermal sulfides mineralization (RE-C1, near Al Kamil); two anomalies suggesting high-temperature Li, Be, B and/or W mineralization (RE-D1 in the southeast of the quadrangle over Tertiary volcanic rocks, centered on Jabal Hadbah, and RW-E over Precambrian plutonic and supracrustal rocks, in the north centered on Jabal Nasir) and RW-A1, which is characterized by anomalous and elevated chalcophile elements and associated with the Samran–Shayban metallic mining district, although anomalous responses extend for many kilometers to the east of the old workings. The lower-priority anomalies show a variety of element associations including a phosphorus-REE anomaly that may be derived from minerals such as monazite and xenotime. The survey has identified regions of high element concentration that should be of interest to the mining industry, and makes a significant contribution to a high-quality geochemical database suitable for environmental monitoring and land-use evaluation.
Abdalla, I.O., Al-Thekair, M., Al-Johani, A.H., Al-Ghanmi, Y., Al-Nashri, M., Sabbahi, A. Al-Eisa, A., and Balkheyour, M., 2010, A Contribution to the Geochemical Atlas of the Kingdom of Saudi Arabia: Geochemical survey of the Rabigh quadrangle, 22D: Saudi Geological Survey Technical Report SGS-TR-2009-11, 99 p., 59 figs., 5 tables, 2 apps.