The gold came to us from the sky in meteorites

The heavy metals, as well as the precious ones, primarily gold and platinum, that were in the earth at the time of its formation sank to the core, in their place the earth's crust was bombarded with metallic meteorites from space 

An extremely precise analysis of some of the oldest rocks discovered on Earth by researchers at the University of Bristol provides clear evidence that the accessible deposits of the heavy metals are the result of a meteorite bombardment that occurred some 200 million years after the planet's formation. The study was published Thursday in the journal Nature.

During the formation of the Earth, the molten iron sank into the core and formed the core. He pulled along with him most of the heavy metals such as gold and platinum. In fact, within the core there are enough heavy metals to cover the entire surface of the Earth in a layer four meters deep.

The transfer of the gold to the earth's core left the outer layer of the earth free of it, but the heavy metals are widespread in the earth's crust tens of thousands of times more than expected. This figure was used in the past to claim that these were the results of a meteor shower that hit the Earth after the core was formed. The excess gold was absorbed into the shell and did not penetrate inside.

However, this theory had no evidence in the experiments, now, thanks to an improvement in the testing capacity, Dr. Mathias Wilbold and Prof. Tim Elliott from the isotope group at the School of Earth Sciences at the University of Bristol were able to analyze 4 billion year old rocks found in Greenland. These rocks were collected by Prof. Steven Morbath of Oxford University.

The ancient rocks provide a unique window into the composition of the Earth shortly after the formation of the core but before the proposed bombardment of the meteorites. The researchers tested the composition of the isotopes of the element tungsten in these rocks. Tungsten is a very rare element (a gram of rock contains only about one ten millionth of a gram of tungsten) and like the other rare elements, it was supposed to enter the core when it was formed.

Like all elements, tungsten also comes in several isotopes, atoms with the same chemical properties but with slightly different masses. The isotopes provide a solid fingerprint about the convexity of the material and the addition of materials to the Earth will be marked with a certain isotope.

Dr. Wilbold discovered a decrease of 15 parts per million in the relative distribution of the isotope 182W between the rock from Garryland and the rocks from today. A small but significant difference is consistent with what is needed to explain the lack of accessible gold on Earth as a byproduct of meteorite bombardment.

Says Dr. Wilbold: "Extracting tungsten from the rock samples and analyzing their isotopic composition to the level of accuracy was a complex operation, given the small amount of tungsten available in the rock. actually. We are the first laboratory in the world that was able to perform such precise measurements."

The meteorites penetrated into the Earth's mantle in a huge convective process. A fascinating goal for future research is to investigate how long the process took. In the end, the geological process created the continents and caused the concentration of the precious metals (and tungsten) in the metal mines where we mine today.

"Our research shows that most of the precious metals on which our economy depends and many of the industrial processes are based on were added to the Earth by a discounted coincidence when the Earth was bombarded with 20 billion billion tons of metals from space."

to the notice of the researchers