Tiny diamonds found within zircon crystals are older than four billion years. They formed shortly after the crust of the earth solidified. They formed deep in the crust, which means that the earth might have cooled more quickly than we thought it did. (Or perhaps they formed before a chunk was taken out for the moon?)
The minerals were found in the Jack Hills region in Western Australia. Australia, like Northern Canada, has been heavily glaciated, exposing deep and old layers of rock.
About 4.5 billion years ago, Earth developed from a cloud of dust around a proto-sun. During its youth, Earth smashed into a planet-size body and its surface temperatures likely soared above 10,830 degrees Fahrenheit (6,000 degrees Celsius). When the molten Earth cooled, the liquid lava gelled into rocks. Details about the rocks and when they began to form, a subject of intense debate, have been limited by sparse data.
One such debate centers on whether early Earth was covered by oceans of hot lava or if the planet’s surface had cooled enough for rock formation and was covered instead by oceans of water.
Zircon crystals, with their high melting point, could provide an answer.
The scientists, led by Martina Menneken of the Institute of Mineralogy, ran chemical analyses of the zircons, finding the ancient crystals (and thus the enclosed diamonds) were more than 4 billion years old. That’s nearly a billion years older than the previous oldest-known terrestrial diamonds and suggests the diamonds were present in material that crystallized within 300 million years of the formation of Earth, the scientists say.After considering different diamond-formation scenarios, the scientists concluded the jewels most closely resembled those found in ultra-high pressure conditions. They interpret the findings to indicate that Earth had a relatively thick continental crust by 4.25 billion years ago.
The study will be published in the Aug. 23 issue of the journal Nature.