Saturday, January 13, 2018

Giant and Hidden Gold Deposits, Wyoming

When I lived in a tent in Atlantic City from about 1983 to 1988 because
the Wyoming Geological Survey was too cheap to provide me with per diem
to rent a cabin while mapping the South Pass Greenstone Belt, I guess I
could have been considered a snowbird who lived at Atlantic City during
summers and Laramie during winters. 
Wyoming is known for its detrital gold found in paleoplacers. These are simply fossil stream placers deposited in the geological past that are now mostly high and dry. Mining these requires transporting water to the paleoplacer, or the paleoplacer to water.  

Where a paleoplacer consists of relatively unconsolidated gravel, it can be mined similar to a sand and gravel operation. If the operation is near a road, the sand and gravel can be used as a by-product for road construction. The opposite may also occur where gold can be extracted as a by-product of sand & gravel operations if it is found such operations have anomalous gold. Where paleoplacers are extremely old, such as in the Witwatersrand of South Africa, the gold is recovered from underground mines to depths of more than 13,000 feet.  

Small paleoplacers are found scattered around the Atlantic City area at South Pass and there are also likely overlooked paleoplacers. The closer these paleoplacers sit to gold-bearing shear zones, the better they should be. To find these on Google Earth, visit the to Atlantic City, Wyoming area. This is where I figured I would end up retiring after I got tired of the Wyoming Geological Survey, but already, the area is getting crowded. Just look at the populations signs!

Ugh! Where are all the people coming from?
Follow the Riverview Cutoff road south of town at an eye altitude of about 10,000 feet using Google Earth. Near GPS coordinates 42°28'45"N; 108°42’58”W I placed a Panorama photo on Google Earth a few years ago close to the northern extent of one paleoplacer. As you look at the area on aerial photography, note the rock foliation (lineation) disappears - this is because the old metamorphic rocks are buried by the younger paleoplacer. On the ground, the paleoplacer contains some scattered rounded rocks that normally can not be seen on aerial photography; however, at 42°28'36"; 108°42’46”W a rounded, white boulder is actually visible on the aerial photos at an eye altitude around 8,300 feet. When you slowly back off the eye elevation to 17,000 or 18,000 feet, you will be able to see the extent of the paleoplacer (it is subtle, but its there). At the eastern extent of the paleoplacer is an old ditch dug by late 19th century to early 20th century prospectors presumably to transport water from Rock Creek to hydraulically mine parts of the paleoplacer and parts of Rock Creek. 

Rock foliation in the Miners Delight formation seen on the side of hills from Rock Creek
(photo by the GemHunter.webs.com).
One large paleoplacer (with reworked gold deposits, or placers) is found south of the South Pass greenstone belt. This is the Dickie Springs-Oregon Buttes paleoplacer and the greenstone belt continues under this large paleoplacer. In 1978, a few members of the US Geological Survey astounded the geological community when they suggested this paleoplacer contained as much as 28.5 million ounces of gold! If valid, that would make this one of the larger gold deposits in the US. But little exploration has occurred of the gold deposit because of its size and lack of water. Even so, past information suggests that reworked portions of the paleoplacer near Dickie Springs (42°18'30"N; 108°51’48"W) has more than a million ounces of gold. This should provide some exciting gold prospecting opportunities. Not only is their gold in the paleoplacer, but in places it has been reworked in modern drainages and there should be ample supplies of gold in drainages in the area. 
Examination of the gravel in the Dickie Springs -
Oregon Buttes paleoplacer to the south of South Pass
at Dickie Springs (photo by the GemHunter).

One of the more popular areas is Dickie Springs because it has water, and gold has been mined in that region in the historical past as well as in recent years. To find Dickie Springs, do a Google Earth search for “Dickie Springs, Fremont County, Wyoming”. When you arrive at the spot, note that Dickie Springs sits in a drainage that flows to the northeast to the Sweetwater River at the edge of the exposed portion of the South Pass greenstone belt (and its not the only drainage). 

Now keep in mind: there is not only a world-class paleoplacer gold deposit siting along the southern edge of the South Pass greenstone belt, but there is also a hidden, world-class, lode gold deposit in this region that supplied the  gold to the paleoplacer. And greenstone belts are known for major gold deposits. So, where is this deposit? Several years ago, Hecla Mining had a possible lead, but their project was terminated by managment. It will likely take detailed geophysical surveys and drilling to find it (or is there more than one?).

Dave Freitag shows a vial of gold recovered from his paleoplacer gold
property at Dickie Springs (photo by the GemHunter).
Oregon Buttes lit up by sunshine. View from South Pass (photo by the
GemHunter).
Gold from the Dickie Springs paleoplacer - photo courtesy of Dr. J. David Love. 

Generalized geological map of the Wyoming
Province should the location of greenstone belts
in Wyoming. South Pass lies in Western Wyoming
at the southern tip of the Wind River Mountains.

The GemHunter lectures to a group of gold prospectors about the geology and gold deposits of the South Pass greenstone
belt and associated paleoplacers (photo courtesy of David Miller).

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