The Bergslagen ore province in central Sweden hosts several rare earth element (REE)-rich deposits, which have recently come back into focus with the increasing demand for REE. In order to understand and potentially predict the occurrence of these deposits, it is crucial to understand the hydrothermal processes that formed them. This study presents new geochemical and mineralogical data on regional alkali alteration zones in the metavolcanic rocks that host the deposits, which show strong depletion of light REE.