MAGMATIC UNDERPLATING, EXTENSION, AND CRUSTAL REEQUILIBRATION - INSIGHTS FROM A CROSS-SECTION THROUGH THE IVREA ZONE AND STRONA-CENERI ZONE, NORTHERN ITALY

The thermal impact of magmatic underplating at various crustal levels is studied along a traverse through the Ivrea-Verbano Zone and Strona- Ceneri Zone in northern Italy. Geochronological and petrologic data ar e compared to a two-dimensional thermal-kinematic model. Field data an d numerical simulation show the strong disturbance of the temperature field in the lower and intermediate crust in relation to magmatic unde rplating leading to granulite- to amphibolite-facies metamorphism as w ell as reequilibration of mineral chemical and isotopic systems. Magma tic underplating leaves a crust with an apparently heterogeneous tecto nometamorphic evolution, as information on the earlier history is pres erved only at upper crustal levels.