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  • Dec 24, 2014
  • Updated: 7:12am

Earthquake

An earthquake, also known as a quake, tremor or temblor, is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.

At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity.

NewsWorld
SCIENCE

Quakes can lead to build-up of gold deposits in earth's crust, study says

PUBLISHED : Tuesday, 19 March, 2013, 12:00am
UPDATED : Tuesday, 19 March, 2013, 3:27am

Solid gold can be deposited in the earth's crust "almost instantaneously" during earthquakes, said a study published in the journal Nature Geoscience.

The gold is formed when a tremor splits open a fluid-filled cavity in the earth's crust, causing a sudden drop in pressure, according to a team of Australian researchers. This, in turn, causes the fluid to expand rapidly and evaporate, and any gold particles that had been dissolved in it to "precipitate almost immediately", said the journal.

"Repeated earthquakes could therefore lead to the build up of economic-grade gold deposits."

The researchers said much of the world's known gold was derived from quarts veins that were formed during geological periods of mountain building as long as three billion years ago.

The veins formed during earthquakes, but the magnitude of pressure fluctuations or how they drove gold mineralisation were not known.

For this study, researchers used a numerical model to simulate the drop in pressure experienced in a fluid-filled fault cavity during an earthquake.

In so doing, they answered a longstanding question about the world's gold resources - how the metal becomes so concentrated from a highly dissolved state to a solid, mineable one.

The study said single tremors would not generate economically viable gold deposits, which were built up one thin coating at a time.

To form a 100-tonne gold vein deposit would take less than 100,000 years, the team wrote.

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