Abstract
In the Ivrea-Verbano Zone, mantle-derived marie rocks have been emplaced in the lower continental crust in contact with mantle peridotite bodies and granulite-facies metasedimentary rocks. One of these bodies, the marie intrusion in the Sesia valley near Varallo and Balmuccia, previously investigated by Voshage et al. (1990) and Quick et al. (1992), probably intruded 270 to 290 Ma ago and assimilated large amounts of crustal material by triggering extensive crustal anatexis. We have studied the mafic-ultramafic complex near Finero in order to compare it with the intrusion near Varallo and Balmuccia. Previous work by Voshage et al. (1987) indicated that in contrast with Balmuceia, the phlogopite-bearing mantle peridotite at Finero contains crustal-type isotopic signatures. This mantle peridotite forms the core of an antiform and is overlain by the three subunits of the marie complex, the strongly layered inner gabbro, the cumulus amphibole peridotite and the massive external gabbro.
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