A recent study has found that zircons, considered as the Earth's "time capsules" being one of the oldest bits of minerals, are not as pure as geologists thought them to be and that research data drawn from them could be doubtful.

Researchers led by geologist Birger Rasmussen of Curtin University in Bentley, Australia analyzed more than 7000 zircons from a portion of the Jack Hills of Western Australia where the rocks are between 2.65 and 3.05 billion years old. They found out that many of the pebbles which contain the zircons have been heavily contaminated and even chemically altered.

In fact, of the 485 zircons under study, about a dozen contained radioactive trace elements that were aged from 2.68 billion years and others 800 million years, when the zircons ranged in age from 3.34 billion and 4.24 billion years old.

"This was a big surprise to us," Rasmussen says, noting that the ages of the inclusions matched the ages of the metamorphic minerals surrounding the zircons.

With these findings, Rasmussen said that conclusions of studies using analyses of zircons and their inclusions, particularly the temperatures and pressures they've been exposed to since their formation, to determine the presence of oceans or of modern-style plate tectonics on Earth more than 4 billion years, could be suspect.

These findings "suggest that analyses of zircon inclusions can't be trusted much at all," Jonathan Patchett, an isotope geochemist at the University of Arizona in Tucson told ScienceLive.

Meanwhile, Allen Nutman, a geochemist at the University of Wollongong in Australia, noted that although the findings casts doubt on some zircon inclusions, others may still provide valuable information. "You don't have to throw away information, you just have to be careful what you do with it," he said.