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