Estonian graptolitic argillites - Ancient ores or future fuels?

Abstract

The Estonian black argillites formed in Late Cambrian and Early Ordovician (Tremadoc) just after the Cambrian evolutionary explosion, nicely illustrated by the famous Burgess shales. The abundant new Cambrian lifeforms were well able to thrive in anoxic poisonous and strongly radioactive waters, rich in U235. They belong to the extensive formation of the Cambrian-Ordovician black shales which form patches in the latitudinal zone extending from Lake Ladoga in the east to the Jutland Peninsula in the west. In the black mud-stones at Sillamäe the most enriched elements are, in the order of biocapture efficiency, molybdenum, carbon, rhenium, antimony, uranium and arsenic. It appears that not only the most unusual chemical composition, but also the very large compositional variability might depend upon even faraway metamorphic processes and long-transported allochtons during the Finnmarkian and Caledonian orogenies. The Sillamäe black shale is certainly a better metalliferous ore than the comparable product from Jämtland, Sweden. It is also a very good future fuel, but only nuclear. The carbon content is too low for anything except providing process heat for production of rare metals. © 2009 Estonian Academy Publishers.