DOLOMITES OF THE MUHU FORMATION (SILURIAN) IN MAINLAND ESTONIA - ASPECTS OF DOLOMITIZATION, PROPERTIES, AND PROSPECTS OF UTILIZATION

. In mainland Estonia the Muhu Formation of the Jaagarahu Stage (Silurian, Wenlock) is represented by secondary dolomites (dolostones) originating from the normal-marine calcareous sediments of the shoal facies belt of the palaeobasin. Five rock types, reef, breccia, microcrystalline, low-argillaceous, and argillaceous dolomites, differing in the lithological composition, properties, and possible fields of use, are distinguished. The chemical composition ofdolomites exhibits close to ideal molar proportions of Ca and Mg for all above-mentioned types of dolomites. The results of the X-ray diffraction study show that dolomites are nearly stoichiometric, with d,,, equalling 2.8850-2.8856 А. The dolomites studied represent the most completely and evenly dolomitized part of the extensive body of pervasive Silurian dolomites.