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Ancient oceans enriched in gold: Australian scientists research

Xinhua, August 4, 2015 Adjust font size:

Australian researchers have struck gold, formulating a new technique to measure how much of the precious metal existed in the world's oceans over the past 3.5 billion years.

Geologists from the University of Tasmania's ARC Center of Excellence in Ore Deposits (CODES) have developed a "time curve series" to show the variation of gold concentration in the ocean over that enormous length of time.

The CODES data indicated that at one stage, 3 billion years ago, the ancient ocean carried 2,000 times more gold than the world's biggest gold bullion depository at Fort Knox, Kentucky of the United States.

In a media release on Tuesday, CODES director Professor Ross Large explained why the ocean was awash with gold during this period: "This was a time when the world's greatest gold ore deposits were formed in South Africa in the Witwatersrand Basin."

"Over the next 400 million years, gold remained high in the oceans and many other important deposits formed, including the Golden Mile in Western Australia."

The research was published in the Earth and Planetary Science Letters this week.

The researchers believe the proportion of gold generated in the shallow crust of the earth indirectly affected the concentration of element found in the ocean.

"This means peak times of gold in the oceans correspond to the best times in Earth's history for gold ore formation," Large said.

At various stages the amount of the shiny metal present in the underwater environment was lean or abundant over the 3.5 million year period.

Large said there were a number of other factors for the peak in the ocean's gold levels 3 million years ago.

"Firstly, there was far more volcanic activity and gold was carried in micro-particles in the volcanic magmas and volcanic gases from deep in the Earth and erupted on the Earth's surface," he said.

"Erosion then transported the gold along with other related elements - arsenic, nickel, antimony, tellurium and mercury into the oceans. The very ancient oceans were therefore enriched in gold but highly toxic." Endi