Tuesday, October 22, 2013

Wyoming Gold

In 1981, Wyoming experience its first gold rush in the 20th century after I released a report on gold assays from samples I collected at Bradley Peak in the Seminoe Mountains (some vein samples running as high as 2.87 opt Au, and altered banded iron formation sample that assayed 1.14 opt Au). Everyone wanted to further investigate this area. Me too! But all of the motel rooms in Rawlins, Wyoming were booked solid by exploration geologists. Not easy to do, because few people want to spend time in Rawlins - its ugly, hot, dry and so the State constructed the State Pen in Rawlins. We think of it as being a not so pleasant place where rattlesnakes run wild and politicians and the former state geologist should take up residence. It also has a new golf course along the interstate that looks like it would compete with the Apache Junction course in Arizona.

In a few years, I would meet a new friend - Dr. Terry Klein with the USGS. Our paths seemed to periodically cross over the years as they did in the Seminoes. Terry would later finish a PhD dissertation in this area where he first recognized komatiite volcanics associated with this greenstone belt, as well as a broad zone of propylitic alteration surrounding the area where I found all of the gold. This altered zone needed to be drilled and still to this day, needs to be drilled. Wyoming had gold, it had a lot of gold deposits, but for some reason, the state was ignored for gold - even though its geology suggested 100 to 500 times more gold should have been found in the Cowboy. Where is all of that gold hiding?

My discovery of significant gold in the Seminoe Mountains was the first of a number of gold rushes I started while working at the Wyoming Geological Survey at the University of Wyoming. And I'm pretty convinced that I would have found more economic gold deposits in Wyoming if I could have stayed a bit longer. But I couldn't stand the sight of my supervisor, and decided it was time to move on.

Normally, a sample like this would get one excited. It is massive cuprite with
some malachite and tenorite (copper ore). But I think I got the entire Sunday
Morning mine ore body in this one specimen.
I had several interesting experiences in the Seminoe Mountains. It is a very quiet place with no one around for miles.

One time I met two interesting people - Charlie and Donna Kortes. All kinds of things in this region are named after them - like the Kortes Dam. Anyway, they wanted me to look for mineralization in the Sunday Morning Prospect. This was a weird mine not too far from the mines on Bradley Peak. After you crawled in the first several feet, the tunnel almost looked as if it had been offset by a fault (which it wasn't), but my theory is that it was a homework assignment for mining engineers from a junior college. The tunnel just dropped down about 7 feet for no apparent reason. So to access the rest of the tunnel, one needed a ladder.

Spinifex textured komatiite from the Seminoe Mountains greenstone belt.
Such rocks are often associated with nickel and gold deposits.
Well, Charlie and Donna brought in two small aluminum ladders and used chicken wire to hook them together so (we?) could get into the rest of the mine. As I climbed down the rickety ladder, Charlie announce he and Donna would wait for me at the mine portal. E-gads! Are these two people (who I had just met) going to sucker me into climbing into this mine and then pull out the ladder, steal my government 4-wheel drive truck with 200,000 miles, and leave me there to die? Well, after I worked my way to the mine face, I went back and - whew - the ladder was still there. I climbed out and told them there was nothing much to see.

Another day, Charlie and Donna drug me out to about a mile from the Miracle Mile on the North Platte River. We were high and dry sitting in a boulder conglomerate. They told me to dig some dirt and pan it for gold. I dug the dirt and took it to the North Platte and panned - "well I'll be a State Geologist's uncle", I thought to myself. Gold! Everywhere I sampled in this dry placer, I got some gold. But heck with the gold - the samples all had distinctly purple to lavender pyrope garnets - the same kind that are found associated with diamond-bearing kimberlites!
The Bradley Peak Hilton - where I spent my summer
vacation mapping the Seminoe Mountains greenstone

Over the years I panned numerous pyrope garnets from this paleoplacer. Every single pyrope garnet we tested with the electron microprobe at the University of Wyoming had diamond-stability geochemistry! That had never happened to us before. Of all of the pyrope garnets I had sampled in the past, only a small percentage had diamond-stability geochemistry. The data indicates there is one heck of a diamond deposit(s) hidden out there waiting to be discovered - and based on the geochemistry of the garnets - it will be rich (and there are likely many diamonds to be found in the region in the paleoplacer and in the North Platte River). This is simply because to have those garnets scattered in the paleoplacer indicates that the host diamond-bearing kimberlite pipe has been partially eroded  scattering part of its diamond budget.

I could never get the state geologist to request for funding in our budget to search for the source of the gold and garnets. But what the heck, state geologists often have much better things to do - there's always good productive geologists to harass to death, after all.

Another interesting experience happened when I was working near Sunday Morning Creek on the North Flank of the Seminoe Mountains. It was very late in the day and time to get off the mountain. I was tired from walking all day and it was hot. My mind said to me - "Hey, watch for rattlesnakes" and just about that time, I stepped on a coiled rattlesnake! Have you ever seen a geologist in heavy hiking boots, a backpack full or rocks and utility belt break the world's record in both the high jump and long jump in one step? Well I did! And yes, I still angry at the Olympic committee. They will not recognize my world record, just because only a rattlesnake, coyote and me witnessed the event. Sometimes you just have to wonder about committees. Years later, when I mapped the Iron Mountain kimberlite district, I tried to break the record again.

Jasperized banded iron formation, Seminoe Mountains, WY