The pairs of intergrown ilmenite and magnetite (Fig. 2e, f) were examined for the estimation of oxygen fugacity (Supplemental Table 6 and Fig. 8). For comparison, we also measured those CA-074 Me from the Jinan gabbro in the interior of the NCC (Huang et al., 2012a and Huang et al., 2012b) and the Tekesi gabbro associated with the Tarim plume in the Southwest Tianshan orogen, NW China (He et al., 2013). Magnetite in the Wulian samples is titanomagnetite with Fe3 +/Fe2 + ratios from 1.31 to 1.59 and TiO2 from 3.31 to 7.13 wt% (Supplemental Table 6; Fig. 8). By contrast, magnetite in the Rushan samples contains extremely low TiO2 with high Fe3 +/Fe2 + ratios close to 2 (Fig. 8a). There is a negative correlation between TiO2 and Fe3 +/Fe2 + of all magnetites (Fig. 8a). Ilmenite in the Wulian samples also has relatively higher TiO2 but lower Fe3 +/Fe2 + ratio than fucoxanthin in the Rushan samples, defining a negative correlation between TiO2 and Fe3 +/Fe2 + (Fig. 8b). Oxygen fugacity and temperature of Fe–Ti oxide crystallization were estimated using the ilmenite–magnetite geothermobarometry program (ILMAT120; Lepage, 2003). Calculated temperature and oxygen fugacity (logfO2) are listed in Supplemental Table 4 and plotted in a temperature vs. logfO2 diagram (Fig. 8c), which shows that Fe-Ti oxides of the Wulian samples were formed in relatively lower oxygen fugacity but higher temperature in comparison with those of the Rushan samples (Fig. 8c). Overall, the Fe-Ti oxides of the Wulian samples are similar to those of Jinan gabbro and the Tekesi gabbro (Fig. 8).
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