SOUTH PASS! Now here is a fantastic gold district in a greenstone belt with potential for some multi-million ounce gold deposits. I spent several years mapping this 450-square-mile greenstone belt and met many wonderful people & prospectors while living in a tent over five field seasons. This is prospector's country, where many gold anomalies have been overlooked and ignored.
I completed eight 7.5-minute quadrangles, one 1:48,000 scale map of the greenstone belt, mapped more than 3 dozen underground mines and differentiate the greenstone belt into formations. During field investigations, I identified >100 gold anomalies. This was a dream come true - what a great place to work.
This research project was initiated in 1983. During 1983 and 1984, 12 field reports and a field guide were published that snowballed into dozens of additional reports and maps on the district. South Pass was Wyoming's principal gold district but no major gold mines were developed. Still the area has intrigue and the more I mapped, the more I was convinced past prospectors and mining companies missed a few attractive targets. Most notable was the Carissa Mine - a potentially 1000 by 1000 by 970 feet deep (at the very minimum) gold lode.
Some projects one might consider include sampling all gold-bearing shear zones from end to end. I estimate about 95% of these remain unsampled. There are tens of thousands of feet of shear structures in this greenstone belt, and ore shoots are structurally controlled by folding. These shoots (or reefs)have short strike lengths, but likely plunge a few thousand feet. Thus sampling the surface of the shears can miss many ore shoots depending on sample separation. In addition, large portions of the shears are buried by detritus.
Then there is the source of the paleoplacer gold at Oregon Buttes and McGraw Flats. Millions of ounces of gold (>30 million ounces) were estimated to be enclosed by these paleoplacers - where did it come from? The gold in the Oregon Buttes district most likely came from a buried part of the South Pass greenstone belt sitting adjacent to the paleoplacer. Looking at the gold flakes recovered in this district, they have morphologies of corn flakes - in other words they did not travel far from their source (see above photo)!
Want more information on this district? Look for our Field Guide for Prospectors and Geologists on Amazon.
GOLD from South Pass - an under-explored greenstone belt.