FIG. 8. Comparison of initial _Os in the Thompson nickel belt (TNB) with mafic and ultramafic systems that are interpreted to have been derived dominantly from mantle plumes. The _Os units are the percentage deviation of an Os isotope composition at any time from that of the chondritic average. The horizontal black line represents the evolution of the chondritic average. Solid points are Os initial ratios calculated from isochrons. The boxes show the range of compositions for isotopically heterogeneous systems. Data sources are as follows: Bilingwe, Zimbabwe (Walker and Nisbet, 2002); Noril’sk, Siberia flood basalt province (Horan et al., 1995); Keweenawan (Shirey, 1997); Deccan, India (Allègre et al., 1999); Pechenga, Russia (Walker et al., 1997); Onega, Russia (Puchtel et al., 1999); Vetreny, Russia (Puchtel et al., 2001b); Alexo, Canada (Gangophadyay and Walker, 2003); Ruth’s Well, Australia (Meisel et al., 2001); Kambalda, Australia (Foster et al., 1996); Boston Creek, Canada (Walker and Stone, 2001); Kostomuksha, Russia (Puchtel et al., 2001b); Gorgona Island, Colombia (Walker et al., 1991); Viet-Song La, Vietnam (Hanski et al., 2004). Shown for comparison is the range of data defined by modern ocean island basalt (OIB; Shirey and Walker, 1988).