Linking growth episodes of zircon and metamorphic textures to zircon chemistry: an example from the ultrahigh-temperature granulites of Rogaland (SW Norway)

In-situ U-Th-Pb analyses by ion-microprobe on zircon in intact textural relationships are combined with backscatter and cathodoluminescence imaging and trace element analyses to provide evidence for growth episodes of zircon. This approach helps: (a) to unravel the polymetamorphic history of aluminous migmatitic and granitoid gneisses of the regional contact aureole around the Rogaland anorthosite-norite intrusive complex; and (b) to constrain the age of M2 ultrahigh-temperature (UHT) metamorphism and the subsequent retrograde M3 event. All samples yield magmatic inherited zircon of c. 1035 Ma, some an additional group at c. 1050 Ma. This suggests that loss of Pb by volume diffusion in non-…