Radiometric methods in geological reconstruction, in the prospecting of georesources and evaluation of hazard

This study deals with a in-situ radioactivity measurements in the rocks with 3 main objectives:1) Assessment of hazards resulting by the use of granitoid rocks as building materials. Based on the specific activities (expressed as Bq kg-1) measured with gamma-ray spectrometer, we have estimates the Activity Concentration Index (I). The (I) values in these rocks vary between from 0,73±0,07 inGrigio Malagato 1,04±0,05 inRosa Cinzia.2) The measurement of40K,238U and232Th performed according to the objective 1) revealed that portable gamma-ray spectrometer is a powerful tool in survey and mapping of intrusive complexes. Two study cases were considered: Buddusò and Arzachena plutons and their surrounding intrusion. These innovative tests show that the portable spectrometer proved high efficacy in real time geochemical discrimination of single intrusion.3) Applied a stochastic-deterministic approach to simulate the Variscan one-dimension geotherm at c.a. 350 Ma and c.a. 300 Ma. Three main sources would have contributed to the thermal budget of the crust: Radiogenic heat production; Moho heat flow and Viscous shear heating. We have collected a large number of thermo-barometric constraints, at 350 Ma and 300 Ma, to compare the geotherm built with the P-T-t path. Results support a radiogenic contribute joined to basal flow enhanced by crustal delamination.