SUBDUCTION OF WATER INTO THE MANTLE - HISTORY OF AN ALPINE PERIDOTITE

The Erro-Tobbio peridotite (western Alps) is a slice of subcontinental mantle that underwent pre-Jurassic passive rifting, followed by sea-f loor hydration and Cretaceous (Alpine) subduction. Analysis of its ext ension- and subduction-related structures and metamorphism suggest the dip below the Adria plate of both the extensional detachments and the subduction plane. High-pressure boudinage structures of rigid metarod ingite within ductile antigorite serpentinite prove that antigorite su rvived subduction and remained stable at eclogite facies conditions. S ubduction of serpentinized peridotites from ophiolite slabs is here co nsidered the most effective mechanism of bringing water to great depth within the mantle.