Deposit Formation Model May Help in Nevada Exploration

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"Models for deposit formation shape how companies explore, mitigating risk."

A team of University of Nevada, Reno and University of Nevada, Las Vegas researchers have devised a new model for how Nevada's gold deposits formed, which may help in exploration efforts for new gold deposits.

The deposits, known as Carlin-type gold deposits, are characterized by extremely fine-grained nanometer-sized particles of gold adhered to pyrite over large areas that can extend to great depths. More gold has been mined from Carlin-type deposits in Nevada in the last 50 years—more than $200 billion worth at today's gold prices—than was ever mined from during the California gold rush of the 1800s.

"Carlin-type deposits are unique to Nevada in that they represent a perfect storm of Nevada's ideal geology—a tectonic trigger and magmatic processes, resulting in extremely efficient transport and deposition of gold," said John Muntean, a research economic geologist with the Nevada Bureau of Mines and Geology at the University of Nevada, Reno.

"Exploration is increasingly targeting deeper deposits. Such risky deep exploration requires expensive drilling. . .Models for gold deposit formation play an important role in how companies explore by mitigating risk."

The team combined decades of previous studies by research and industry geologists with new data of their own to reach their conclusions, which were written about in the Jan. 23 early online issue of Nature Geoscience magazine and will appear in the February printed edition. The team relates formation of the gold deposits to a change in plate tectonics and a major magma event about 40 million years ago. It is the most complete explanation for Carlin-type gold deposits to date.

"Our model won't be the final word on Carlin-type deposits," Muntean said. "We hope it spurs new research in Nevada, especially by people who may not necessarily be ore deposit geologists."

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