Structural and petrological constraints on the tectono-metamorphic evolution of the Massa Unit (Alpi Apuane)

A study of the metamorphic and tectonic evolution of the Massa Unit in the Alpi Apuane Metamorphic Complex shows that this unit suffered relatively high-pressure conditions (peak higher than 0.8 GPa) and was exhumed during a multiphase history. The first stage of exhumation occurred during Tertiary continental collision between Adria and Sardinia/Corsica and was associated with the thrusting of the more deeply buried chloritoid + kyanite-bearing Massa Unit on top of the less deeply buried chloritoid + Pyrophyllite-bearing Apuane Unit. The subsequent stages of exhumation were shared by the two metamorphic units and were coeval with the beginning of crustal extension related to the opening of the Tyrrhenian Sea. Copyright (C) 2000 John Wiley & Sons, Ltd.