Ello Maremäe¹, Endel Lippmaa¹
(1) National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

Abstract: Estonian Dictyonema Shale – Occurrence, chemical composition and chemical technology

The Early Ordovician (Tremadoc) graptolitic argillite, known as the Dictyonema Shale, crops out on the southern coast of the Gulf of Finland in northern Estonia. The shale correlates with the Ordovician Alum Shale of Sweden.

The Dictyonema Shale is a low-grade oil shale. It contains 80–90% mineral matter and 10–22% organic matter. The organic matter is rich in nitrogen, sulphur and oxygen. The ratio of carbon to hydrogen in the organic matter is about 9, the calorific value of the organic matter is 34 MJ/kg. The oil yield of the organic matter by Fischer assay is 15–30% and averages 25%. For the whole rock, the oil yield is 2–4 (4)%, and the calorific value is 5.9 MJ/kg.

The Dictyonema Shale is a potential multi-mineral resource. The content of more than 12 microelements in the shale exceeds, in most cases, that found in clays by 2–100 times. Commercially important elements are uranium (35–300 ppm), molybdenum (50–400 ppm) and vanadium (350–1000 ppm). There are several chemical technologies for separating these elements including the formerly top-secret industrial processing of uranium at Sillamäe in northeast Estonia immediately after World War II.

Today, there is no economically and environmentally acceptable technology for the recovery of oil or metals from the Dictyonema Shale. However, the shale is a prospective resource for the future.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana