Comparative Geochemistry of Metals and Rare Earth Elements from the Cambrian Alum Shale and Kolm of Sweden
- John Parnell,
- Ye Lianjun and
- Chen Changming
Published Online: 3 APR 2009
Copyright © 1990 The International Association of Sedimentologists
Sediment-Hosted Mineral Deposits: Proceedings of a Symposium Held in Beijing, People's Republic of China, 30 July-4 August 1988
How to Cite
Leventhal, J. (1990) Comparative Geochemistry of Metals and Rare Earth Elements from the Cambrian Alum Shale and Kolm of Sweden, in Sediment-Hosted Mineral Deposits: Proceedings of a Symposium Held in Beijing, People's Republic of China, 30 July-4 August 1988 (eds J. Parnell, Y. Lianjun and C. Changming), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303872.ch17
Department of Geology, The Queen's University of Belfast, Belfast BT7 INN, UK
- Published Online: 3 APR 2009
- Published Print: 27 SEP 1990
Print ISBN: 9780632028818
Online ISBN: 9781444303872
- Scandinavian alum shale - metal-rich black shale;
- uranium, enriching Upper Cambrian shale;
- Alum shale formation of Scandinavia;
- Sydbillingen core;
- Ranstad open pit mine;
- Dictyonema-bearing shales
The Cambrian Alum Shale Formation of Sweden is a metal-rich black shale. The metal distribution, however, varies with stratigraphy as well as organic carbon content and shows increases for certain metals in areas of tectonism. In the non-metamorphosed areas, the elements uranium, molybdenum, vanadium and lead are enriched by factors of 2—4 relative to other black shales. The organic-rich (50% organic carbon) kolm of the Upper Cambrian shale is more enriched in uranium (0.5%), radiogenic-lead (200 ppm), yttrium (800 ppm) and heavy rare earth elements (HREE, e.g. ytterbium 45 ppm), but depleted in other elements (molybdenum, vanadium, nickel). Normalizing to aluminium accounts for the major and rock-forming elements in the kolm that are the same as the surrounding shale, but not for uranium, lead, yttrium and HREE in kolm.
In many shales, increased metal or trace element contents can be accounted for by parallel increases in organic matter, pyrite or phosphate as hosts or sites. However, increases in content of trace elements are often not correlated with the content of hosts (sites) for the metal and trace element contents in non-metamorphosed alum shale or kolm. Therefore a combination of unusual source rocks (rich in uranium and other elements) coupled with selective element transport and efficient concentration by organic matter in an unusual depositional environment is suggested as a method of element enrichment.
In the metamorphosed areas, the carbon content of the Cambrian shales is similar to the non-metamorphosed areas but vanadium (0.2%), nickel (500 ppm), zinc (500 ppm), cadmium (10 ppm) and barium (1500 ppm) are greatly increased. Epigenetic addition of metals from external source(s), rather than internal redistribution, is suggested to account for increased amounts of metals (vanadium, nickel, zinc, cadmium and barium) in the metamorphosed/tectonically affected areas.