Combined quantification of anisotropy and inhomogeneity of magmatic rock fabrics : an outcrop scale analysis recorded in high resolution

Abstract

Magmatic mineral distribution patterns in a syntectonic syenite pluton have been recorded at high resolution over several square metres on quarried faces. The anisotropy and inhomogeneity of K-feldspar and mafic mineral distribution patterns have been quantified using two methods originally based on fractal geometry. (1) Map-counting, based on box-counting, illustrates an inhomogeneity on the decimetre to metre scale and highlights diffuse structures that can be related to mafic schlieren or felsic dykes that are not visible on the rock surface. (2) We have developed a mapping of rock fabric anisotropy (MORFA) method that leads to the detection of further magmatic structures that are not visible in the field. With MORFA a magmatic lineation and its variation over large areas is determined, as well as fabrics on the decimetre to 1 m scales, which possibly represent flow or fracture structures in the crystallising magma