A Study of Two-Dimensional Grain Sequences in Rocks
The visual aspect of crystalline fabrics in thin or polished sections under the microscope is captured by digitizing the outlines of all recognizable grain profiles (from 250 to 2500) over areas of 3 to 6 cm2. Digital image processing of the textural data obtained is applied to extract quantitative aspects not detected readily by human vision such as the frequency distribution of contacts between grains belonging to the same or to different phases. The methods described are of importance when a model of crystallization can be expressed in terms of geometrical relationships between grains. Furthermore, such relationships correspond to physical characteristics of a rock.
This contribution reviews recent work in texture analysis and proposes some new techniques in which computer processing and petrology are useful mutually for quantitative measurement and recognition. Examples of applications to metamorphic rocks and intrusive rocks are described in which image processing leads to the following results: (a) the probability of a grain to be surrounded by other grains, (b) the mapping of particular grain sequences, and (c) the identification and statistical analysis of individual grain contacts.
KeywordsMetamorphic Rock Binary Image Textural Data Markov Random Field MarkOvian Property
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