Laser 40Ar/39Ar analyses of phlogopites from kimberlites and thier xenoliths: constraints on eruption ages of Southern African and Siberian kimberlites and mantle volatile compositions - Pearson, D.G.; Kelley, S.P.; Pokhilenko, N.P.; Boyd, F.R. (International Kimberlite Conference: Extended Abstracts, 1995)