Acknowledgements
M. Zucali and G. Rebay are thanked for stimulating discussions and helpful suggestions; M. Roda constructive review greatly improved the manuscript. Funding by PRIN 2008 ‘Tectonic trajectories of subducted lithosphere in the Alpine collisional orogen from structure, metamorphism and lithostratigraphy’. A. Risplendente provided the technical support at the Dipartimento di Scienze della Terra “A. Desio”, where the analytical work with the EPMA has been performed.