Geology how does gold form

One involves the explosion of supernova stars and the resulting nuclear fusion creating atoms of gold, and the other, the collision of neutron stars that results in a gamma-ray burst, one of the most powerful explosions possible.

In August , the presence of heavier elements, including gold, was detected using gravitational wave detectors during the first observation of the collision of two neutron stars. What these two events have in common is the presence of nuclear energy, which is required to combine lighter atoms into heavier ones. Where is gold found? In its natural form, it is found deep in the layers of the earth where it is transported by water, molten lava and volcanic eruptions, and earthquakes.

Geologists have found gold in rocks as old as 4. The Witwatersrand, one of the most gold-rich mining areas in the world, is located in a km radius crater in southern Africa, thought to have been caused by a meteor strike over 2 billion years ago.

This theory reinforces the idea that gold was brought to earth from the cosmos by asteroids. Gold is also found in our oceans. Since these temperatures do not occur at the surface, the nuggets must have originated deep underground. If the nuggets are not formed where they are found, but weathered from gold-rich ore, the original source may still be nearby.

Read more at Gold Nuggets Reveal their inner secrets. Hydrothermal replacement deposits are primary deposits transported in very hot fluids dissolved with elements such as silicon, iron and sulphur from deep within the earths interior.

Over the millions of years as the earth formed and cooled down these fluids rich in elements such as gold penetrated the cracks, fissures and cavities in the earths crust. They are deposited in faults, quartz veins, Doleritic sills, fractures, balsaltic rocks, in fact the deposits could have intruded into any sort of rock structure. The deposits we are interested in as primary gold are Epithermal Deposits formed within about 1km of the earths surface in volcanic rocks.

Over the life cycle of the earth there have been countless upheavals and weather cycles so these deposits can be available to the gold prospector at surface or just below the surface if you know what to look for. The Supergene Enrichment process forms by saline water dissolving minerals at the near suface weathering environment carriage of the material downwards to the water table where there is a secondary enrichment process.

Other Secondary Gold Deposits are alluvial and eluvial gold deposits. What does the Origin of Gold mean anyway? But a study published today in Nature Geoscience 1 has found that the process can occur almost instantaneously — possibly within a few tenths of a second.

The process takes place along 'fault jogs' — sideways zigzag cracks that connect the main fault lines in rock, says first author Dion Weatherley, a seismologist at the University of Queensland in Brisbane, Australia. When an earthquake hits, the sides of the main fault lines slip along the direction of the fault, rubbing against each other. But the fault jogs simply open up. Weatherley and his co-author, geochemist Richard Henley at the Australian National University in Canberra, wondered what happens to fluids circulating through these fault jogs at the time of the earthquake.

What their calculations revealed was stunning: a rapid depressurization that sees the normal high-pressure conditions deep within Earth drop to pressures close to those we experience at the surface. For example, a magnitude-4 earthquake at a depth of 11 kilometres would cause the pressure in a suddenly opening fault jog to drop from megapascals MPa to 0.

By comparison, air pressure at sea level is 0. Eventually, more fluid percolates out of the surrounding rocks into the gap, restoring the initial pressure. Big earthquakes will produce bigger pressure drops, but for gold-vein formation, that seems to be overkill.

More interesting, Weatherley and Henley found, is that even small earthquakes produce surprisingly big pressure drops along fault jogs. That, Weatherley adds, might be one of the reasons that the rocks in gold-bearing quartz deposits are often marbled with a spider web of tiny gold veins.

Small bits add up. Weatherley says that prospectors might be able to use remote sensing techniques to find new gold deposits in deeply buried rocks in which fault jogs are common. Weatherley, D. Nature Geosci.