GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 1.3 157 Fig. 3 - Mechanical and acoustic results from triaxial experiment on CarraraMarble deformed up to 180MPa confining pressure. (A) Dashed line shows the differential stress derived from the mechanical experiment. Continuous lines represent energy of attenuation obtained from acoustic measurements in three angles, 0° (black), 22.72° (red), and 51.48° (blue). Brown line represents crack density variation throughout the experiment. strength envelopes are characterized by maxima of the order of 1000 MPa associated to deeper BDT depths (usually > 10 km). In addition, when we consider the ‘ cold ’ geotherm, a strain rate value of 10 -15 s -1 or greater, and we assume extensional stress conditions, the selected mafic rocks deform only in brittle conditions. We could further observe that the depths to the BDT, when occur, and the intercepting temperatures span a range greater than those obtained for sialic rocks. In the same way, the mean viscosity values at the BDT are approximately one order of magnitude greater than those associated to the sialic rheologies. However, we demonstrated that, variations in Q s , at the BDT depth are less affected by the input rheology and geotherm than variations in the rock‘s viscosity. The implication is that,