LAUSR

Abstract The 1.49 Ga Norra Karr complex (Sweden) consists of deformed and metamorphosed peralkaline nepheline syenites that contain eudialyte-group minerals as the major host of high field strength elements and rare earth elements. Earlier studies revealed the presence of distinct generations of eudialyte-group minerals and clinopyroxene of magmatic and metamorphic origin. Here, we present the trace element characteristics of the different generations of rock-forming minerals. The trace element chemistry of eudialyte-group minerals mimic whole-rock compositions and display well-developed negative Eu-anomalies and strong Sr- and Ba-depletions in chondrite-normalized diagrams. They imply that the Norra Karr rocks developed by intense fractional crystallization from an alkali basaltic parental magma. Our data further illustrate that eudialyte-group minerals do not strongly fractionate the geochemical twins Zr/Hf, Y/Ho and Nb/Ta during magmatic processes. The transition from a magmatic to metamorphic environment is marked in EGM by a drop in Y/Ho and Nb/Ta. The exceptional enrichment of heavy rare earth elements in late metamorphic eudialyte may result from residual enrichment: light rare earth elements (and Nb) were preferentially mobilized to form local secondary light rare earth-rich rinkite-group mineral assemblages, while the heavy REE stayed behind and formed heavy REE-rich eudialyte. Magmatic clinopyroxene shows a clear preference for Hf over Zr, while on a subunit scale a negative correlation of the total REE in cpx and in EGM is noticed. Both indicate that early cpx fractionation would not only increase Zr/Hf of the evolving melt, but also affect the REE deportment in major HFSE-hosts.