HADEAN · The Earth in Transition: from Earliest Crust to Earliest Preserved Rocks

Current knowledge of the nature and origin of the earliest crust on Earth comes largely from studies of the mineral zircon. The oldest zircon crystals from Jack Hills in Australia provide a wealth of information and represent a time capsule of what the Earth was like from 4.4 to 4.0 Ga during the Hadean. These zircons are detrital grains preserved in much younger rocks, and no known rocks of this age have survived on Earth. By applying the most up–to-date technologies to various isotopic systems in these zircons, it has been possible to deduce that continental crust and oceans formed early in Earth`s history and that the planet cooled more quickly than was previously realised. The aim of this proposal is to compare the information acquired from these detrital grains with comparable new data to be obtained from the earliest known rocks on Earth. These ancient rocks are preserved in Antarctica, Canada, China, Greenland, Western Australia and Swaziland. Extensive investigation of these rocks will allow us to characterize further the nature of the earliest preserved crust and, more importantly, to document what changes took place from the formation of the earliest zircons (4.4 Ga) to the oldest preserved crust (4.03 Ga) and to evaluate why so few Hadean rocks survived on Earth. This period represents the ‘dark ages’ in terms of Earth history and marks the onset of stable conditions on the Earth that set the stage for a habitable planet.""