NASA funded research has recently found that the Earth's collision with moon-sized planetary bodies known as planetesimals has resulted in the accumulation of large quantities of metal and rock-forming minerals in the Earth's mantle and crust.
The researchers at the Southwest Research Institute, or SwRI, and the University of Maryland have created high-resolution impact simulations and found that the planetesimals could have either penetrate to the Earth's core or could have bounced back into the space to move out of the planet.
The researchers believe that the bombardments during the "late accretion" which started during the Planets formation period and diminished before 3.8 billion years have contributed to about 0.5% of the Earths mass. These collisions resulted in the deposition of rare metals like platinum, iridium, and gold on Earth.
According to the research paper published in the journal Nature Geoscience, Simone Marchi and his colleagues found that there was larger scale addition of rare metals to Earth. This was during the period after the formation of the moon. The metals tend to chemically bond with the metallic iron and resulted in the formation of Earth's core. The research model found that the materials added to the planet had been 2-5 times more than previously thought.
Simone Marchi said, "These results have far-reaching implications for Moon-forming theories and beyond. Interestingly, our findings elucidate the role of large collisions in delivering precious metals like gold and platinum found here on Earth."
Researchers from the University of Granada (UGR) have found that the gold has been brought to the earth's surface through volcanic eruptions. Jose Maria Gonzalez, a researcher at the UGR said, "The search for gold has motivated migrations, expeditions, and even wars, but its origin is one of the main questions in the field of mineral deposits genesis."
Scientists believed that the gold had been formed in the core or mantle. Xenoliths from the Earth's mantle reach the surface through volcanic eruptions. Gold particles as thin as the human hair have been found in these Xenoliths.
According to a theory, the Africa and South America had been a part of the same continent during the formation stage of the planet. The 'molten plume' from the core separated the continent into two while adding rich metals deposition to the mantle. The constantly deposited metal had huge reserves of gold in them contributing to the huge gold deposits in the continents.
Jose Maria Gonzalez said, "This time the process was caused by the movement of a tectonic plate under another, allowing the circulation of metal-rich fluid through the cracks, which precipitated the metals and concentrated them near the surface."