CLINOPYROXENE-OLIVINE-ILMENITE MEGACRYST ASSEMBLAGE IN KIMBERLITE FROM THE UDACHNAYA PIPE

Abstract

The picroilmenite-rich (up to 60 vol % ilmenite) kimberlite found in the Udachnaya-Vostochnaya Pipe is a unique case. A zone enriched in large picroilmenite and olivine phenocrysts (from 3-5 to 20 mm or more) was found in a large kimberlite block from the Udachnaya-Vostochnaya Pipe at a depth of more than 400 m. Separate picroilmenite megacrysts grow together with clinopyroxene or contain large clinopyroxene inclusions (up to 1 cm or more). This phenomenon is unique in the following aspects: (1) association of three megacryst minerals (first finding of clinopyroxene megacrysts in kimberlite of the Udachnaya Pipe); (2) strong enrichment in picroilmenite megacrysts; (3) absence of serpentinization and, consequently, fresh appearance of minerals.