Nine samples over the ancient rock belt record a regional tectono-thermal event at ∼2.6 Ga.
2.6 Ga can be regarded as the early and late Neoarchean break in the region.
Most of zircons, whether magmatic or metamorphic, have δ18O values of +4.5‰ to +6.5‰.
However, a tonalite sample has metamorphic zircons with low δ18O values (+1.09‰ to +3.25‰).
This suggests that meteoric water must be involved in the metamorphic and anatectic process.