PDF (RUS) Lu-Hf isotope composition of zircon from syenites of the Sakharjok alkaline massif, Kola Peninsula

Abstract

This study examines zircon from the alkaline and nepheline syenites of the Sakharjok massif magmatic (2.645 ± 7 Ma), hydrothermal (1.832 ± 7 Ma) and metamorphic (1.784 ± 22 Ma) stages. Zircon from the alkaline syenites shows lower ɛHf and ɛNd values compared to that from ocean island basalts (OIB) suggesting their mantle-derived prololiths, are close to the CHUR in terms of isotopic composition. It is assumed that the formation of the Neoarchean alkaline Keivy province resulted from the plume-lithospheric interaction triggered by the uplift of a Neoarchean plume that stipulated the processes of metasomatic alterations and subsequent partial melting of the subcratonic lithospheric mantle and crustal rocks. The initial melts of the Sakharjok massif could probably form during the reactivation of the plume activity that occurred 20—30 million years after the emplacement of alkaline granites of the province by selective melting of the metasomatized lithospheric mantle rocks.