Secondary alteration in eclogites from kimberlite pipes

An analcime-type zeolite has been found in eclogite xenoliths from a kimberlite pipe. Analytical data obtained for the primary pyroxene (omphacite) and secondary minerals (mica, analcime, clay) indicate that the xenoliths have been contaminated by K,Rb and Cs, which are important for the study of the origin of eclogites. Metasomatic alteration of an eclogite during the intrusion of the kimberlite may be followed by further contamination of the eclogite by the migration of elements during the weathering of the kimberlite. For many elements abundance data must be determined on separated primary eclogite minerals and data obtained on whole-rocks should be treated with some circumspection.