Two Major Patterns of Single Mineral Replacement in Granites

On the basis of difference or consistency of crystallographic orientations between replacive and replaced minerals, replacement textures in granites can be classified into two patterns:hetero-oriented replacement, e.g., clear albite rim, swapped albite, K-feldspathization, muscovitization, quartzification, beryllization, calcitization, etc. and co-oriented replacement, e.g., deanorthitization of plagioclase, co-oriented albitization of K-feldspar, muscovitization, and chloritization of biotite, etc. Hetero-oriented replacement predominates. The unreplaced part of the replaced mineral survives in the replacive mineral without changing its crystallographic orientation.