Figure 5. Major element abundances versus Mg# of Pilbara and Isua ultramafic samples. Geochemistry of arc peridotites, other compiled >3.2 Ga ultramafic rocks from the Isua and Pilbara areas, and MELTS modelling results are also plotted for comparison. References of compiled >3.2-Ga ultramafic rocks are listed in theFig. 1 caption. All data are presented using anhydrous values (i.e., all major element abundances are normalized to zero LOI and 100 wt.% total). Data for arc peridotites are from Chin et al. (2014) and references therein. Primitive mantle values are from McDonough and Sun (1995). The mixing lines represent mixing between 20% depleted primitive mantle and mid-ocean ridge basalt (MORB) end-members H, L, and D (Elthon, 1992). Details of MELTS modelling are in Chin et al. (2014). Data sources: Serpentinites from the Nob Well Intrusion of the East Pilbara Terrane: Geological Survey of Western Australia 2013 database. Compiled ultramafic rocks from the Isua supracrustal belt: Friend and Nutman (2011), Szilas et al. (2015) and Waterton et al. (2022). Compiled ultramafic rocks from enclaves in meta-tonalite south of the Isua supracrustal belt: Friend et al. (2002); Van de Löcht et al. (2020). Ultramafic rocks from the Tussapp Ultramafic Complex: McIntyre et al. (2019).