The Thickness and Thermal State of the Lithospheric Mantle beneath the Yubileinaya Pipe (Alakit-Markha Kimberlite Field, Siberian Craton)

The results of study of the chemical composition of chromdiopside xenocrystals from a heavy mineral concentrate of kimberlites from the Yubileinaya pipe are presented. The mantle paleogeotherm was reconstructed using single-crystal clinopyroxene geothermobarometry and the FITPLOT program. The paleogeotherm was found to correspond to a surface heat flux of 34.8 mW/m(2). The estimated thickness of the lithosphere beneath the Yubileinaya pipe is 230 km, with a "diamond window" interval of approximately 105 km (from 125 to 230 km). To compare the paleogeotherm, the thicknesses of the lithosphere, and the "diamond window" beneath the Yubileinaya and Udachnaya pipes, the mantle paleogeotherm beneath the Udachnaya pipe was reconstructed. The resulting values for the heat flux, lithospheric thickness, and "diamond window" under the Udachnaya pipe are 34.7 mW/m(2), 233 km, and 108 km, respectively. The diamond-bearing capacity of the Yubileinaya pipe is approximately two times lower than that of kimberlites of the Udachnaya pipe. Consequently, the observed difference in the diamond potential may be related not only to the thickness of the sampled lithosphere and the "diamond window," but also to other petrological parameters, such as the degree of manifestation of diamond-generating and diamond-destructive metasomatism.