The age of the Kleva intrusion, southeast Sweden

The Kleva nickel-copper mineralization is situated within a gabbro-diorite intrusion on the border between the late Svecofennian rocks of the Oskarshamn-Jonkoping belt and rocks of the slightly younger Transscandinavian Igneous Belt (TIB). The sulphides present in the mafic intrusion are pyrrhotite, chalcopyrite, pentlandite and pyrite, occurring as massive mineralization, disseminations and thin, predominantly chalcopyrite-bearing veins. Age determinations of the gabbro-diorite were conducted to determine the age of the mineralization and its regional context. U-Pb analyses of baddeleyite (TIMS) and zircon (SIMS) from the gabbro-diorite and related rocks indicate an age of c. 1.79 Ga for the Kleva intrusion, broadly coeval with the TIB-rocks in the area, but younger than the late Svecofennian rocks. Further studies will help to constrain whether the sulphide mineralization was modified during later alteration, regional tectonism and metamorphism.