Las Vegas, Nevada, is famous for extracting gold from visitor’s pockets, but the northern area of the state has given miners more gold than the California gold rush.
Over the past 50 years, the area near Carlin, Nevada, has yielded more than $200 billion worth of gold in today’s prices. But no one was sure how the lustrous metal got there.
A team of researchers from the University of Nevada recently developed a model for how the gold deposits formed. Their research was published online in the journal Nature Geoscience.
The researchers found that changes in the movement of the Earth’s crust about 40 million years ago, coupled with a major event involving magma, the liquid rock inside the Earth, led to the creation of the Carlin gold deposit.
By comparison, most gold on Earth is found in old river basins where the gold was washed into the area and then remained there as the mountains grew up around them, such as the case in California and South Africa, or as the result of hydrothermal activity where hot springs bubble up the gold through fissures in Earth’s crust.
“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, of the University of Nevada at Reno in a press release.
The nanometer sized nuggets of gold are attached to pyrite. The tiny grains of gold were too small to be noticed by early prospectors, so mining of the Carlin gold didn’t start until 1961. Now, clusters of “Carlin-type” deposits have been found throughout northern Nevada.
“Understanding how these deposits formed is important because most of the deposits that cropped out at the surface have likely been found. Exploration is increasingly targeting deeper deposits. Such risky deep exploration requires expensive drilling,” said Muntean.
Though this research didn’t directly point to new deposits, it tells geologist and miners what to look for. “Knowing how certain types of gold deposits form allows one to be more predictive by evaluating whether ore-forming processes operated in the right geologic settings. This could lead to identification of potential new areas of discovery,” said Muntean.
IMAGE 1: Twin Creeks gold mine, Nevada, USA; Carlin-style mineralization in Mesozoic sedimentary rocks (Geomartin, Wikimedia Commons)
IMAGE 2: Goldstrike Mine, Carlin Trend, Nevada, the largest Carlin-type deposit in the world, containing more than 35,000,000 ounces gold. (USGS, Wikimedia Commons)
IMAGE 3: Gold embedded in pyrite. From Colorado (Rob Lavinsky, Wikimedia Commons)