“…The grey region is for the forearc basalts from Reagan et al (2010); the black dashed lines are linear regression lines of data from active arc sites (Reagan et al, 2010); (d) Cr versus Y plot (after Pearce, 1982) [Colour figure can be viewed at wileyonlinelibrary.com] F I G U R E 9 (a) NiO versus Fo plot for olivines, the field for forearc peridotites is from Ishii, Robinson, Maekawa, and Fiske (1992), fields for the different mantle peridotites, ultramafic and mafic rocks are from Constantin, Hékinian, Ackermand, and Stoffers (1995). The arrow shows the fractional crystallization trend and is from Constantin (1999); (b) Cr# of spinel versus Fo content of olivine, the olivine-spinel mantle array (OSMA) given by Arai (1994), field for boninite restite from Johnson et al (1983); field for high Mg andesite restite from Tatsumi and Ishizaka (1981); boninite sample points are from Johnson et al (1983), Johnson, Jaques, Hickey, McKee, andChappell (1985), and Ramsay, Crawford, and Foden (1984); (c) Ternary Cr-Al-Fe 3+ plot for spinel after Stevens (1944), the different field are from Barnes and Roeder (2001); (d) Cr# versus Mg# plot for spinels, the field for boninites is from Dick and Bullen (1984), the fields for harzburgite, lherzolite, and metamorphic spinel is from Stevens (1944), the low greenschist metamorphism field is from Irvine (1967); (e) 100 Cr# versus TiO 2 plot of spinel, fields after Kepezhinskas, Taylor, and Tanaka (1993). Data of Songshugou ultramafic forearc (b,e) taken from Cao et al (2016) [Colour figure can be viewed at wileyonlinelibrary.com] which might be due to low-temperature reequilibration during metamorphism.…”