Alum shales, Sweden

Many therefore believe that the enrichment of uranium in marine black shales is strictly related to the presence of organic matter in the sediments. This last, along with the H2S, is deemed to be ultimately responsible for the reduction of uranyl ion to the insoluble form, uraninite. The Chattanooga Shale (U.S.A.) and the Alum Shale (Sweden), are the two best-known examples of uraniferous black shales. 

Black shale Uraniferous alum shale in Sweden, the Chatanooga shale in the USA, the deposit of Gera-Ronneburg in the eastern part of Germany. 

There are obviously higher values in Scandinavia than in southern Europe and in many local areas such as Cornwall in the United Kingdom (Cliff et al., 1987) there are some substantially higher concentration areas. In Sweden there is a clear effect of alum shale concrete on indoor radon levels both from the perspective of increasing the concentrations indoors, but also because of an increased percentage of the population living in houses of such construction (Swedjemark et al., 1987). Thus, the largest fraction of people live in houses with radon concentrations below 110 Bq/nr. 

In addition to their energetic value, oil shales have also been used as sources for other materials, such as alumina, ammonium sulphate, phosphate, sodium carbonate, S, U, V, and Zn (Murray 1974). In the early 17th century, potassium aluminium sulphate was extracted from the Alum Shales in Sweden for use in the tanning and textile industry. It was only by the 19th century that hydrocarbons were being extracted from these Alum Shales while, in the 1960s, their content of U and V was being exploited (Dyni 2000). 

Typical activities of building materials, such as bricks and concrete, in the UK and USA are in a similar range (20 to 50 Bq kg-1) (Nero, 1983), but granite used in older houses in Cornwall has about 100 Bq kg -1 of radium (O Riordan et al., 1982). In Sweden, Hultqvist (1956) found about 1000 Bq kg-1 radium equivalent gamma activity in lightweight concrete made from alum shale. 

Dahl J. E. P., Hallberg R., and Kaplan I. R. (1988) Effects of irradiation from uranium decay on extractable organic matter in the Alum Shales of Sweden. Org. Geochem. 12, 559-571. 

Uraniferous Alum shales, Billingen-Ranstad, Sweden Quite often the black shales show a clear uranium enrichment, the Lower Palaeozoic shales containing millions of tonnes of uranium with average contents grading from some 10 to almost 100 ppm U. Their extraction cannot be envisaged with present technology for environmental and technical reasons and under present market conditions. 

In the Vastergotland and Narke provinces of Sweden, however, the Alum shales (average 70 ppm U) present a 2- to 3-m thick horizon (Fig. 3) enriched in uranium, probably by a diagenetic process, to an average of some 300ppm U. These shales are of Middle and Upper Cambrian plus Tremadoc age, and. have a thickness of several tens of metres. 

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