Mineral age dating

13-Nov-2019 16:21

More important, uranium and lead can move around within a crystal, or even escape or enter the zircon.This mobility can throw off the lead isotope count used to calculate the zircon ages, and is the source of the decades-long controversy over the Jack Hills zircons' Methuselah lifespan.By zapping single atoms of lead in a tiny zircon crystal from Australia, researchers have confirmed the crystal is the oldest rock fragment ever found on Earth — 4.375 billion years old, plus or minus 6 million years. Confirmation of the zircon age holds enormous implications for models of early Earth."We've proved that the chemical record inside these zircons is trustworthy," said John Valley, lead study author and a geochemist at the University of Wisconsin, Madison. Trace elements in the oldest zircons from Australia's Jack Hills range suggest they came from water-rich, granite-like rocks such as granodiorite or tonalite, other studies have reported.The lead hasn't wiggled around enough to throw off the ages.

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The key finding, that lead atoms stick close to home inside this primeval zircon, means age estimates based on uranium-lead dating techniques are accurate, the researchers report.

Before 1955, ages for the Earth based on uranium/thorium/lead ratios were generally about a billion years younger than the currently popular 4.5 billion years. old Earth is reviewed and deficiencies of the uranium/lead method are discussed.

The basic theory of radiometric dating is briefly reviewed.

The researchers painstakingly counted individual lead atoms within the oldest-known zircon with a recently developed technique called atom-probe tomography.

Inside the zircon, lead atoms clustered together in damage zones just a few nanometers wide.

The key finding, that lead atoms stick close to home inside this primeval zircon, means age estimates based on uranium-lead dating techniques are accurate, the researchers report.Before 1955, ages for the Earth based on uranium/thorium/lead ratios were generally about a billion years younger than the currently popular 4.5 billion years. old Earth is reviewed and deficiencies of the uranium/lead method are discussed.The basic theory of radiometric dating is briefly reviewed.The researchers painstakingly counted individual lead atoms within the oldest-known zircon with a recently developed technique called atom-probe tomography.Inside the zircon, lead atoms clustered together in damage zones just a few nanometers wide.The ancient Australian crystals date back to just 165 million years after Earth formed, and have survived tumbling trips down rivers, burial deep in the crust, heating, squeezing and a tectonic ride back to the surface.