The Oldest Pillow Lavas, 3.8-3.7Ga from the Isua Supracrustal Belt, SW Greenland: Plate Tectonics Had Already Begun by 3.8Ga

Abstract

The presence of pillow basalts in the 3.8-3.7 Ga Isua supracrustal belt, Southern West Greenland indicates the presence of liquid water on early Earth around 3.8-3.7 Ga. The total thickness of pillow basalts is up to 1.0 km for the thickest unit, suggesting an ocean depth of at least 1.0 km. The rigidity of the Early Archean oceanic lithosphere can be calculated from the petrologically estimated mantle potential temperature of 1450℃ and ocean surface temperature below 100℃. The results show that the oceanic lithosphere was sufficiently rigid to operate modern-style plate tectonics only 0.7-0.8 Ga after the formation of the Earth.