Figure 5
From: Diversity in early crustal evolution: 4100 Ma zircons in the Cathaysia Block of southern China
Oxygen fugacity (fO2) versus Ti concentration and calculated temperature by the titanium in zircon thermometer26,40.
This plot is made based on a compilation (Table S5) of seventy-three >3800 Ma zircons. The temperatures were calculated assuming unit activities of TiO2 and SiO2 and no pressure correction. Reaction curves of fO2 buffer assemblages (HM, hematite–magnetite; NNO, Ni–NiO; FMQ, quartz–fayalite–magnetite) and the boundary between SO42− and S2− predominance in silicate magmas (dashed line) are from Chou42 and Wallace and Carmichael56 respectively. The black dashed curve represents the oxygen fugacity shown by the two average analyses from the magmatic zonation of the two grains.
