- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
Xenoliths of semipelitic rocks that show metamorphic segregation structures occur in the granitic rock at Rosguill. The commonest type is an intergrowth of cordierite, muscovite, microcline, and biotite surrounded by a mantle of microcline, and coarser at the center. Others consist of a fine-grained intergrowth of biotite and microcline mantled by coarse-grained material or large grains of microcline mantled by biotite. The segregations are mineralogically similar to the ground-mass and probably formed by differential transfer of material within a localized zone of the ground-mass.