Geochemical exploration methods for niobium and rare earth elements in the Oslo Graben have been studied using the occurrence at Sæteråsen, Vestfold as a test area. The deposit consists of two lens-shaped bodies of aphyric trachytic lava within a sequence of porphyritic latites and trachytes. The extrusive rocks
are intruded by nordmarkite and larvikite. Samples of various types of stream sediment, strcam moss, soil and rock have been analyzed for the total contents of Ba, Ce, La, Nb, Rb, Sr, Th, U, Y and Zr by an X-ray fluorescence method. The relationships between the concentrations and ionic potentials of trace
elements in stream-moss samples and different types of sediment and rock samples are discussed. Streammoss samples gave significant La-and U-anomalies in the area, white no distinct stream-sediment anomahes were encountered.