Abstract
Five granitic masses in the Raniah area were a matter of concern regarding their suitability for domestic uses in the term of their natural radioactivity and the hazard indices. Raniah area is located between latitudes 28 degrees 15.-28 degrees 18.N and longitudes 42 degrees 30.-42 degrees 50. E about 350 km east of El-Taif city, Kingdom of Saudi Arabia. The granitic masses are named as; JabalMaslukh, JabalWaridat, JabalKawr, JabalHarashef and Jabal AlKhathami granites. Petrographically, they were assigned as alkali feldspar granites to alkali granites with perthite, quartz and plagioclase as the major mineralogical components together with sensible amounts of biotite and alkali amphiboles. Zircon appeared as the common accessory mineral in addition to the apatite and opaques. Geochemically, they exhibited the alkalinity and per-alkalinity affinities and originated from high differentiated magma in the within-plate tectonic environment as A-type granites. The radiometric measurements pointed to that the granitic masses of J. Maslukh, J. Kawr and J. Harashef have the lowest 226Ra and 232Th concentrations while the highest values were provided by J. Al-Khathami granite. The calculated radium-equivalent values were ranged between 134.07 Bqkg(-1) (J. Maslukh) and 255.13 Bqkg(-1) (J. Al-Khathami) while the adsorbed dose rate recorded its lowest value as 64.39 nGyh(-1) and its highest value as 122.83 nGyh(-1) by the granites of J. Maslukh and J. Al-Khathami respectively, also the same behavior were found in the values of the external and internal hazard indices. The annual indoor effective dose, the annual outdoor effective dose and the total annual effective dose values of all the examined granitic rocks recorded their highest values as 0.603, 0.151 and 0.754 (mSv) respectively in J. Khathami which are lesser than the safe criterion limit (1 mSv) for general public. Although some values of the excess lifetime cancer risk are slightly elevated but they are generally either within the safe limit (1.45 x 10(-3)) or very close.