EXTENSIONAL PROCESSES DRIVEN BY LARGE-SCALE DUPLEXING IN COLLISIONAL REGIMES

Syn-orogenic extension and 'normal-sense' pressure-break contacts in c ollisional 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 sh ow good agreement with geologically-derived stretching and pressure br eak values characterizing the western Tuscany core complex of central Italy, which was chosen as a test area. The results of our study suppo rt the hypothesis that 'normal-sense' pressure breaks of the order of a few kbars and syn-collisional extension in excess of 50% can be prod uced in the roof sequence by deformation within growing subduction-col lision complexes. Copyright (C) 1996 Elsevier Science Ltd.