en Medical Physics Medical Physics تحقيق بديع Original Research <p><strong>Background:</strong> The concentrations of radionuclides like ²²⁶Ra, ²³²Th and ⁴⁰K and the dose rate are measured in igneous and metamorphic rock formations in and around Chickmagalur. A total of 236 samples from 13 different locations around study area were analyzed. <strong>Materials and Methods:</strong> The activity concentrations of the three radioactive elements were determined for mean period of 25000 s using HPGe (GMX - 10190) detector and the dose calculations were made using standard formulae. <strong>Results:</strong> The mean activity concentrations in igneous rocks recorded were 36.6 Bqkg^-1, 73.2 Bqkg^-1 and 992.3 Bqkg^-1 for ²²⁶Ra, ²³²Th and ⁴⁰K respectively. The mean activity concentrations in metamorphic rocks were 17.2 Bqkg^-1, 28.1 Bqkg^-1 and 617.8 Bqkg^-1 for ²²⁶Ra, ²³²Th and ⁴⁰K respectively. Assuming 20% occupancy factor, the corresponding mean annual effective dose due to igneous and metamorphic rocks were 169.6 &micro;Sv and 90 &micro;Sv respectively. <strong>Conclusion:</strong> The concentrations of radionuclides were found to be in similar with global and Indian average ^(1-3).</p> Radionuclides, Igneous rock, metamorphic rock and effective dose. 183 187 http://ijrr.com/browse.php?a_code=A-10-1-470&slc_lang=en&sid=1 S. Manjunatha manjunatha_s@yahoo.com 790031947532846007508 790031947532846007508 Yes Department of Physics, PES Institute Technology and Management, Shimoga, 577204, India A. Jayasheelan 790031947532846007509 790031947532846007509 No Department of Physics, GFGC, Sira, Karnataka, India P. Venkataramanaiah 790031947532846007510 790031947532846007510 No PG Studies in Physics, Manasagongotri, Mysore, India