ON THE CORRELATION BETWEEN THE COMPOSITIONS OF MANTLE INCLUSIONS AND PETROCHEMICAL VARIETIES OF KIMBERLITES IN YAKUTIAN DIATREMES

Abstract

The compositional characteristics of mantle xenoliths of the grospydite and coesite depth subfacies from the Internatsional'naya, Aikhal, Udachnaya-West, Udachnaya-East, Yubileinaya, Mir, Zarnitsa, Komsomol'skaya, Sytykanskaya, Yakutskaya, Zapolyarnaya, Komsomol'skaya-magnitnaya, and Novinka pipes are correlated with the petrochemical population models of the pipes. The relative occurrence frequencies of various xenolith types were compared with the relative abundances in their host pipes of Ca- and Mg-kimberlites belonging to the modal populations for the pipes considered. Linear relationships were found between the abundances of Ca- and Mg-kimberlites and the contents of deformed and coarse lherzolites, respectively. The abundance of alkaline kimberlite (>1.2 wt % K2O) in the pipes correlates with the amount of pyroxenite xenoliths; and magnesian eclogite content, with the ratio Na2O/(Na2O + K2O) of the kimberlite. Ca-kimberlites are common in all fields of the Yakutian kimberlite province, whereas Mg-kimberlites were found only in a few fields, most representative of which are Malobotuobinskoe, Verkhnemunskoe, and Kuoikskoe. The results were interpreted in terms of processes in the melt-residue system. Ca-kimberlite was derived from a pyrolite-wehrlite undepleted source leaving deformed lherzolites as residues. Mg-kimberlite was produced at high degree of melting yielding a dunite-harzburgite residue. The development of the Botuobinskaya and Munskaya kimberlite-bearing systems in Paleozoic time formed satellite centers of kimberlite formation in the Nakynskoe and Alakitskoe fields.