Friday, October 18, 2013

On Dry Washers, Desert Gold, and Working Dry Ground (Part 10)

 (Desert placers come in all shapes and sizes.)

There are essentially six types of desert or dry placers you should be aware of. Undoubtedly many of you know these well, but for those who don't, let's take a closer look at one of these deposit types.

EOLIAN:

Essentially, eolians are wind-driven or wind-deposited placers in the Western and Southwestern United States as well as other parts of the world at large. Eolian dry placer deposits are not very common and although they're said to exist in some well-known desert locations, I've never come across one in my checkered mining career. Most eolian placers will contain small gold grains, thin, flat flakes, or very fine gold for obvious reasons...it would take some pretty stiff straight-line winds to lift even small gold nuggets into the air, carry them some distance, and finally drop them into an eolian deposit. It should be noted here that the gold contained in eolian placers most often comes from other sources like exposed and eroding ledges, veins, and stringers (just as in most other types of placer deposits).

Finding a "standard" desert eolian deposit wouldn't be an easy task for any of us, methinks. For one the thing the concentration factor in this type of deposit isn't bound to the normal rules of gold deposition (even the vagaries of dry gold deposition, for that matter) so knowing where to search for one becomes problematic at best. A deposit like this could be either localized or widely distributed. So, a small deposit might be next to a tree or bush, near a small rock outcropping, or a larger one spread in thin paystreaks across the desert for miles and miles (and so on). This means that dry washes, gullies, benches, or terraces would NOT be likely starting points to find an eolian. Tracking one to its source would not necessarily be an easy task either, since desert winds could carry small particles of gold (and heavy black sands as well) great distances from their original source.

Blown In, Blown Out

Without much in the way of real real proof I'll go out on a limb here and say that I suspect most eolian gold deposits are quite shallow as well. The only caveat here would be if the winds in a given region were consistently strong in specific locations at regular times of the year. In that sort of situation, it's quite possible that successive thin layers of eolian placer gold could be deposited one atop the other into a relatively "rich" deposit. I've been an avid student of gold prospecting and mining history for over 35 years now and I've yet to come across an account (personal, historical, or otherwise) that described a significant eolian placer gold find. On the other hand, many "experts" (geologists and other earth scientists) contend that there are significant eolian placers scattered throughout the world, in locations as diverse as Eastern Europe, Russia, the Baltic, Mongolia, and sub-Saharan Africa. Remember, the key word here is "significant."

I can easily hear those gears turning 'round and 'round in your heads as you wonder how eolians could exist in non-desert gold areas like those typically found in Eastern Europe and Russia. Here's what's surmised: It's believed that long ago in the Proterozoic period or epoch many of these eolian placers could have formed within shallow seas that dried up when oxygen began to fill our atmosphere and iron-rich soils containing hematite became more prevalent. Once dry, the gold or other metals or heavy minerals could have easily been blown out to form some extensive eolian deposits. Another theory says that in the Cenozoic Period (when mammals replaced the dinosaurs) existing eolian gold was blown into wet sediments, thereby entrapping the yellow metal in shallow deposits. Take your pick (or take both if you like).

Features

In an area known as the Eastern European Platform at a location called Timan Ridge, extensive eolian placers from these periods have been found. They have very specific features to them, including:
  • Distribution over a wide area.
  • Paystreaks that strike in a consistent direction.
  • Paystreaks that are typically very shallow in thickness.
  • Gold in the form of small grains and very thin, flat flakes. 

    (Small gold grains like these are often found in eolian placer deposits.)

The Timan Ridge eolian placers are extensive in area but how rich they truly are (or were) remains to be answered. (In other words, show me the money.) Just the same, I decided to throw this info into the mix to show you that larger eolian gold deposits are out there and not just the smaller and localized deposits I suspect exist in the U.S.

Characteristics

If you look at the four bullets above describing the main features or characteristics of the Timan Ridge placers you probably have a pretty good idea of what to look for in terms of searching for or identifying a larger eolian placer deposit. Let's look at those characteristics again:

1) Distribution over a wide area (most likely by prevailing winds.)

2) Paystreaks that strike in a consistent direction (following the direction of prevailing winds; S, N, SE, SW, etc.).

3) Paystreaks that are very shallow (no consistent forces of deposition or accumulation other than the winds themselves).

4) Gold in the form of small grains or thin, flat flakes (gold that is more easily wind-borne and carried aloft).

I don't know about you but I'm not exactly rushing out the door to prospect for eolian-type placers. Still, gold is gold and were I to stumble upon an eolian, you can bet the farm I'd be shoveling and scooping those shallow paystreaks and feeding them into my dry washer.

Best to you all.

(c)  Jim Rocha (J.R.) 2013

Questions? E-mail me at jr872vt90@yahoo.com

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4 comments:

  1. Hello Jim, I'm not sure about this one.....wind or water should work pretty much the same way, but I would think the wind deposits would be really rare. For one thing the wind changes direction where water stays more or less the same. I know very, very little about desert prospecting, if you say these exist, I believe you 100%. I bet they would be very tough to find though. Seems the better bet would be to find the nugget pile the wind couldn't blow away!! After all, it has already done away with the annoying fine stuff.... Thanks again Jim, and please don't think I'm knocking this post.I truly am not. I never thought about wind depositing gold before, so once again, I've learned something new!! Gary

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  2. JR
    I read your posts with enthusiasm regularly. However, I don't agree with you on this. An eolian placer forms when the lighter mateial blows off of the gold, leaving the gold concentrated in place. Anyway, keep up the posts & the attitude. We need more of you in our world right now.
    Jack M.

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    Replies
    1. Well, we'll have to agree to disagree on this I guess. The existing mining literature talks about "depositing," not "uncovering." I myself term what you're talking about as a "reverse eolian." It's the subject of my next post. Thanks for commenting and for your ongoing support! J.R.

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  3. Well Gary, as I said in the post I've never come across and eolian placer deposit myself. Yet, they do exist out there somewhere! Ma Nature does some strange things when it comes to gold and this is one of them. Best, J.R.

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