Uranium Mineralizations and age Relationships in the Precambrian Bedrock of Central and Southeastern Sweden

Abstract

This paper summarizes studies on the genesis of uranium ores in the Precambrian bedrock of Central and southeastern Sweden. The occurrence of uranium in the mineralizations described was detected during the boom period 1950–1960. None of these occurrences is of economic value. Several different paragenetic types occur, the most common probably being the pitchblende-bearing vein fillings and disseminations of uraninite in iron ores of Central Sweden. The well known Co-Ni-Bi-U paragenesis also occurs, as well as iron deposits possibly being mechanical accumulations and containing uraninite and monazite supposedly of detrital origin. Alteration of uranium minerals is light although a thin coating of secondary uranium minerals may occasionally be observed. More frequent is the formation of thucholite and radiogalena. To correlate the uranium mineralizations with major Precambrian events, minerals and rocks with stratigraphic key positions have been dated by the U/Pb and Rb/Sr whole rock method. As a result the age relationships in the Precambrian bedrock of Central and southeastern Sweden are also discussed.