Extensional processes driven by large-scale duplexing in collisional regimes

Syn-orogenic extension and ‘normal-sense’ pressure-break contacts in collisional regimes have been modeled by considering the behaviour of a stationary roof sequence undergoing layer-parallel stretching above a growing duplex showing an antiformal stack geometry. Model results show good agreement with geologically-derived stretching and pressure break values characterizing the western Tuscany core complex of central Italy, which was chosen as a test area. The results of our study support the hypothesis that ‘normal-sense’ pressure breaks of the order of a few kbars and syn-collisional extension in excess of 50% can be produced in the roof sequence by deformation within growing subduction-collision complexes.