Pictures: Marginal Border Series (MBS)

Colloform banding near the western margin of the Skaergaard intrusion, Mellemø. The centre of the intrusion is to the right. The transition between the tranquil and banded divisions are recognised by the first appearance of modal layering. This layering, commonly referred to as colloform banding, consists of alternating semi-vertical sheets of melanocratic and mesocratic gabbro. The sheets shows broad convex structures towards the centre of the intrusion separated by narrow troughs. They are believed to have formed by material frozen to the magma chamber walls after the onset of magma convection. Note the small pegmatite and granophyre pods towards the left in the photo. Photo by Jens C. Andersen.

© 2003