Quantification of flow patterns in sheared tonalite crystal-melt mush: Application of fractal-geometry methods

摘要

Fractal-geometry-based analysis techniques offer simple and efficient ways for analyzing magmatic fabrics that are otherwise difficult to describe quantitatively. This study shows an application of two different methods on flow patterns observed in a syntectonic magmatic body injected into the lower crust. XZ and YZ rock cuts are scanned, and the scans are automatically transferred to binary patterns of mafic and felsic minerals. These are analyzed by boxcounting as well as the modified Cantor-dust method. Box-counting leads to characterization of the entire patterns, proves their fractality in two different scale ranges, and yields information about magma mingling and grain-aggregate forming processes. The modified Cantor-dust method quantifies the anisotropy of pattern complexity and represents a potentially powerful method for determination of shear sense during magmatic flow. Both methods represent useful tools specifically for analyzing diffuse magmatic fabrics and for connecting field-related studies with analyses on the microscale. Keywords Fabric quantification - Box-counting - Modified Cantor-dust method - Magmatic flow - Syntectonic intrusion