Key points:
- Ultramafic rocks of the Isua supracrustal belt and the East Pilbara
Terrane can be interpreted as crustal cumulates.
- A crustal cumulate interpretation is not diagnostic – these rocks can
form in all proposed Archean tectonic settings.
- Ultramafic rocks of the Isua supracrustal belt do not require
>3.7 Ga plate tectonics.