X-ray photoelectron spectroscopy on fracture surfaces of carrara marble specimens crushed in compression

Neutron emission measurements were made, by means of a He3 detector, on Carrara marble rock specimens under compression. While granite generated neutrons −due to piezonuclear reactions involving fission of iron into aluminum− this phenomenon did not occur in marble under crushing. In this paper, the external and fracture surfaces belonging to Carrara marble specimens crushed during the compression tests were analyzed by X-ray Photoelectron Spectroscopy (XPS). XPS quantitative compositional analyses were carried out in order to detect any variation in Carrara marble composition due to brittle failure of cylindrical specimens. A decrease in O, Ca and Mg as well as an increase in C content was observed on the fracture surfaces with respect to the external ones. These transmutations involve elements (O, Ca and Mg) with an equal number of protons and neutrons, like their reaction products. For this reason the microchemical analyses suggest piezonuclear reactions without neutron emissions in marble crushed specimens.