A team of researchers has devised a new model that describes how some of Nevada’s unique gold deposits were formed, which may help exploration geologists find similar deposits around the world.
The deposits, known as Carlin-type gold deposits, are characterized by extremely fine-grained, nanometer-sized particles of gold incorporated in pyrite and distributed over large areas that can extend to great depths.
More gold has been mined from these deposits in Nevada in the last 50 years – over $225 billion worth at today’s gold prices – than was ever mined during the California gold rush of the 1800s.
The recent Nevada gold boom started in 1961 with the discovery of the Carlin gold mine, near the town of Carlin, located in Northern Nevada. It was discovered at a spot where early westward-moving prospectors no doubt missed the gold because it was too fine-grained to be seen.
Since the 1960s, geologists have found clusters of these “Carlin-type” deposits throughout northern Nevada. These deposits constitute the second largest concentration of gold on Earth after South Africa. Geologists have long speculated on how they were formed.
Recently, researchers from UNLV and the University of Nevada, Reno combined results from decades of previous studies with fresh data of their own to reach new conclusions. The resulting publication appeared in the February issue of Nature Geoscience, which can be found online at .
The research 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.
The researchers include Jean Cline, a professor of geology at UNLV and a leading authority on Carlin-type gold deposits; Adam Simon, an assistant professor of geoscience who provided new experimental data and his expertise on the interplay between magmas and ore deposits; John Muntean, a research economic geologist with the Nevada Bureau of Mines and Geology at the University of Nevada, Reno; and Tony Longo, a postdoctoral fellow who carried out detailed microanalyses of the ore minerals.
“The published research provides insights that may be applied by exploration geologists to locate similar deposits in other areas around the world,” Cline says. “It also provides suggestions as to why Nevada is the only currently known location for these unique deposits and their vast gold resource.”
The work was funded by grants from the National Science Foundation, the United States Geological Survey, Placer Dome Exploration, and Barrick Gold.
