Formation of silicic crust on early Earth and young planetary bodies in an Iceland-like setting

Four billion years ago, Earth’s surface was covered with a thick basaltic crust and, similar to other rocky planets and the Moon, parts of this basaltic crust underwent partial melting to produce silicic crust. On Earth, silicic crust grew into the continents. An analogue of a pre-subduction early Earth and rocky planetary bodies is found in Iceland, where poorly understood granitic rocks are encased in thick basaltic crust away from any active subduction zone. Here, we investigate these Icelandic granitoids to understand the mechanisms that generated the Earth’s oldest continents, and silicic rocks on Mars and Venus. New geochemical data from silicic Icelandic intrusions, show that the granitoids are formed through partial melting of the Icelandic crust, but are compositionally unlike early Earth continental material. We show that intra-crustal partial melting of basalt can potentially form silicic material on other planetary bodies but cannot produce the first continents on Earth.