The Use of Growth Microfabrics and Transmission Electron Microscopy in Understanding Replacement Processes in Carbonates

Crystal growth features of all scales potentially record information on crystal growth directions. Most growth features resolvable with optical microscopy or scanning electron microscopy have the potential of being inherited, at least in part, from a precursor phase. However, certain small-scale growth microstructures (generally resolvable with the transmission electron microscope), because of their dimensions, have virtually no chance of being inherited. Their presence and relative orientations are products of the growth of the crystal in which they occur. Comparing the orientations and distribution of the growth microstructures with those of larger scale growth features can help to determine if a crystal has been replaced and can enhance interpretations of replacement microfabrics. The use of such features is limited in calcites due to the scarcity of diagnostic microstructures. However, in most sedimentary calcian dolomites such smaller-scale features are ubiquitous. In this chapter, with the aid of examples of dolomite crystals, we present the basic concepts regarding use of orientations of growth features at all scales for interpretation of replacement microfabrics.