Metamorphism and Anatexis in the Mafic Complex Contact Aureole, Ivrea Zone, Northern Italy

Emplacement of mantle-derived magma (magmatic accretion) isoften presumed or inferred to be an important cause of regionalgranulite facies metamorphism and crustal anatexis. The juxtapositionof mafic cumulates and regionally distributed granulite faciesrocks has led some to consider the Ivrea zone (northern Italy,Southern Alps) as an important exposure that demonstrates thiscausal relationship. However, regional PTt paths indicated bymetamorphic reaction textures and PT conditions inferred fromgeothermobarometry indicate that the emplacement of mafic plutonicrocks (Mafic Complex) at the Ivrea zone occurred during decompressionfrom ambient pressures at the regional thermal maximum. Fieldand petrographic observations, supported by PT estimates, indicatethat regional retrograde decompression and emplacement of theupper parts of the Mafic Complex probably accompanied extensionduring the Late Carboniferous–Early Permian. A spatiallyrestricted decompression-melting event accompanied final emplacement,depleting supracrustal rocks enclosed by an