Is Sulfur the Key in Quest for Gold?


"New finding could help gold explorers find areas more likely to contain deposits."

A new understanding of how gold-rich magma forms in the presence of sulfur may help in the hunt for gold. To date, about 165,000 tons has been mined, according to the World Gold Council. But while new exploration turns up new mines, not all of earth's gold is easy to find.

"Almost every gold mine has been found from rocks on the surface of the earth," said Economic Geologist Robert Linnen, highlighting California's gold rush as one example. "If you want to find gold now, you have to look for the more difficult stuff."

But how do you find gold that is 100 meters or more below ground?

Linnen suggests beginning with a deep knowledge of how gold deposits form.

Sulfur may be a key ingredient in that recipe, according to his recent study.

While still hotly debated among some geologists, one of the origins for gold mines is thought to be within melts deep in the earth's mantle that then erupt at the upper crust, where they form deposits.

"If that's the case, then we want to understand how the gold comes out of the mantle and gets transported to the surface. . .not all magmas form gold deposits," Linnen said.

"The solubility of gold in sulfur-rich magmas was thought to be very, very low," said Linnen, describing the tendency of a substance to dissolve in another medium.

Based on a series of experiments, the researchers now suggest that sulfur's presence actually increased the amount of gold they found dissolved in magma by up to eightfold, depending on certain chemical conditions. The new finding could help future gold explorations focus on areas more likely to contain deposits like rock formations high in sulfur. Beneath extinct volcanoes in the western U.S. might be one good place to start looking, Linnen said.

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