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.The researchers painstakingly counted individual lead atoms within the oldest-known zircon with a recently developed technique called atom-probe tomography.
– Nature lovers beware, environmental models used by researchers at the University of New Hampshire are showing that the effects of climate change could be much stronger by the middle of the 21st century, and a number of ecosystem and weather conditions could consistently decline even...
Geologists have carefully sorted out more than 100,000 microscopic Jack Hills zircons that date back to Earth's early epochs, from 3 billion to nearly 4.4 billion years ago.
(The planet is 4.54 billion years old.) The crystals contain microscopic inclusions, such as gas bubbles, that provide a unique window into conditions on Earth as life arose and the first continents formed.
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.