Estimation of heat rate generation of natural radioactivity of magma surrounding hot Springs of Mahallat, Iran

In this research magmas (igneous rocks) of 300 hectares area covering of hot springs of Mahallat zone of Iran were studied. Twenty samples of outcrops of magmas were collected. In order to obtain homogeneous fine powder, part of all samples were crushed by jaw and ball milling and dried and passed through mesh number 40 and packed in Negin containers and sealed. Thin cross section were prepared for all samples and mineral components were determined in mineralogy laboratory. Specific activities of 226Ra, 232Th and 40K of all samples were determined using gamma ray spectrometry method employing high purity germanium (HPGe) detector with its electronic system. Specific activities of these radionuclides in samples obtained from 22.15 ± 1.34 to 62.68 ± 3.76, from 10.69 ± 1.43 to 40.55 ± 2.15 and from 59.99 ± 5.07 to 1467.30 ± 17.48 in Bq/kg respectively. Heat rate generation due to radioactivity decay for samples calculated that varied from 0.69 to 1.82 in µW/m3. The mean Heat production of magma with ten cubic kilometer volume obtained as 13.60 kW and the energy for increasing of water temperature with yields of 35.5 l/s from 15º C to 100º C is necessary 12.7 kW. Therefore consideration level of radioactivity and long life of magma of this region and expansion in conic form under hot springs seem to be the resource of heat due to radioactivity decay of 235U, 238U and 232Th series and 40K.