The enigmatic dolomite

Abstract

Since the first description of dolomite, over the past two centuries there has been a great deal of progress with respect to knowledge on the genesis of this rock. Based on inferences emerging from the intense research that has taken place, relevant genetic models have been developed. Over a number of years and after considerable debate, it is now generally accepted that large, dolomite bodies with a wide extent were formed from lime mud or limestone via mineral replacement; furthermore, the dolomite mineral may also have been precipitated as a cement in pore spaces. The current paper provides a brief review of the main stages of the history of dolomite research and displays the main problems which have hampered the understanding of crucial aspects of dolomite-forming processes. The development of the proposed concepts for the interpretation of the observed phenomena and the suggested dolomitization models are also discussed. The paper presents the basic lithological, petrographic and geochemical characteristics of the dolomites and the commonly-applied methods for observation and measurement of the rock properties. According to our current knowledge, it summarizes the general criteria and mechanisms of dolomitization and provides an overview of the most important dolomite-forming processes. The latter take place in various depositional environments: namely, marine and lacustrine, and diagenetic settings (for example, shallow, intermediate, and deep burial). In the second part of the article, the dolomite occurrences in Hungary are considered, along with several case studies from the dolomite-rich Transdanubian Range and Tisza Megaunit. The case studies demonstrate that every dolomite body exhibits remarkably distinct features, formed as the result of multi-stage processes. These processes are mainly determined by host-rock properties, the consecutive dolomitization processes, the evolution of local structures, and the regional geodynamical setting.