New gamma-ray spectrometry methods for estimating K, U, TH concentrations in rocks of the Sardinia batholith

In this PhD thesis are collected the results of a research project in the field of nuclear geophysics developed with the scientific collaboration between the Department of Natural and Territorial Sciences of the University of Sassari and the Department of Physics and Earth Sciences of the University of Ferrara. In particular, the research has focused on two main themes: the first part of the work has addressed the problem of the content of natural radionuclides in rocks as an instrument of their lithological characterization, geochemistry and orogenetic, while the second part deal with the realization of a collimated gamma spectrometer for in situ measurements. The abundances of 40K, U and Th in the Corsica-Sardinian Batholith in the N-E of Sardinia were investigated with 545 in situ gamma spectroscopy measurements with portable detectors NaI(Tl) and 167 measurements of natural radionuclides on rock samples using HPGe detectors. On the basis of the data obtained were processed high-resolution thematic maps of the distribution of radionuclides as well as radiometric ternary map, which show excellent agreement with the geological maps of the region. The second part of the thesis describes a new portable and collimated NaI(Tl) spectrometer, which has been calibrated successfully using the FSA method with the NNLS constraint. The results of the measurements show good agreement with the measured concentrations with independent instruments (HPGe).