Regional geochemical uranium prospecting in Finland

Organic-rich lake sediments were sampled over a 6000-km2 area in Karelia, eastern Finland. In addition to several smaller anomalies, the investigation indicated an extended zone of anomalously high uranium in lake sediments along the contact between Karelian schists and Pre-Karelian rocks. Loss on ignition correlated with the uranium content. Two methods of calculating uranium content with respect to the organic material were investigated. The distribution of uranium in the sediments of individual lakes was studied. It was found that central lake samples may fail to indicated isolated mineralizations in adjacent bedrock. A comparison between lake and stream sediments indicated that stream sediments may be used to complement lake sediment grids in areas of low lake density. (author)