A question about gold deposition in a non standard model

[Ragnor]

So lets say you have this creek. The average grade of the slope over several miles is above 40% slope. It's steep. The stream bed is 10'-15' wide, walled on both sides by slopes averaging 60% grade. Nigh impassable. The entire course is on bedrock with small deposits of alluvium in the few flatter area's 10'-50' long. There are also several log jams. Now at some point a land slide occurs during rapid snow melt. A dam or dams is formed high on the slope. A landslide occurs higher still flowing down the creek at high velocity. It plows into these log dams, bursting them as it goes. This adds exponential volumes of water and debris as it accelerates down the steep bedrock slope of the creek. The steep walls of the ravine containing and guiding this massive slurry of earth and stone and logs. A surge wall some 30+ feet tall of churning doom comes slamming down the canyon with unimaginable force. Not even bedrock dikes can withstand the force of this moving mass and are torn away and added to the slurry.

Now at a lower point a road grade has been established that crosses this ravine. Rock has been filled over a culvret some 75 feet high at the crossing point and a large volume of material has filled in above the road grade from a previous flood event some 20 years ago. The force of this massive land slide tearing down the valley comes bounding off of a waterfall at rediculous speed carrying unquantifyable amounts of energy. The mass of this moving volume strikes the lower staionary deposit and road grade with such force that it literally explosively replaces the former deposit. My best analogy is croquet, when you whack one ball with another and take it's place.

Standing in the creek bed imagining what that actually would have been like to experience is truelly a terrifying wonder. I have seen evidence that at least one elk experienced this horror first hand. It's bones are litterally stripped clean and skattered along the stream course lower down.

The material that came to rest at the base of the old waterfall is completely unsorted. Large logs are covered by boulders and gravel and jut out at every angle. The gravels show little or no sign of bedding or sorting.

So I ask, in a scenario like this where does the gold deposit? Will it be mixed in all throughout the debris deposit? Will it be under the one or two logs that miraculously filled a low pressure zone and remained in the stream bed? So far I have focused on the areas with the largest boulders and the shallowest bedrock. But I still feel I am missing something. Has anyone on here ever successfully explored a flood/landslide deposit like this and figured out where the gold had a tendancy to accumulate? If so, do you mind filling me in on this non standard type of stream bed erosion and sorting?

My best method so far has been metal detecting for pieces of iron that came down from old mines and then cleaning out the areas where I find them.

 

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[kcm]

If the slurry is more liquid than solid, I'd think the gold would try to act its normal self and settle towards the bottom, especially on such a long downhill run - like a giant sluice without classification. If more solid than liquid, then it may well be scattered throughout the settled mass.

Gold has a high SG (Specific Gravity), which means it is heavier when suspended "in water". The more solid a slurry is, the more SG gets thrown out the window.

You write a good piece - ever think of becoming a writer??

 

[Terry Soloman]

I've had some experience with flash flood drain offs in the Arizona mountains. I have found that in the situation you describe, the gold settling pattern is like a shotgun. Up high the gold stays more or less centered in the stream. Where the log jams explode and are washed down the hillside, I have found small pockets thrown up on the steep benches, then centering again. If you can get a tractor or Bobcat and move the wood and rock pile at its center, and run the material under that, well, you'll be buyin' a case of Good Beer that night!

 

[Ragnor]

Here are some pics I took yesterday of where the material settled out. Kind of shows the scope of what I described.

 

[63bkpkr]

Some fella here on T-net talks about gold as being lazy. I suspect the scenario of increasing the SG of the water with mud will effect the normal characteristics of Au, that is being less lazy. Then again think of the activity of Bazooka Sluice box especially the catch tray, that's a bunch of dirt and the heavies still settle to the bottom. There are a lot of possibilities in the scenario you've described as well as pictured. That must-a been one heck of a ride, and I'd have loved to have seen it from a respectable distance!

That tangle of wood and rock is a mess that will exist for some time Even if one were to go at it with some serious equipment. I am still partial to the Lazy Gold concept even though the conditions were Extreme and as Terry has pointed out/experienced, he's found extreme flood gold in some unique locations. Some of this "where's the gold" question might be gotten at if one knew the history of the typical size of the gold found along that stream. If the typical gold was thin, 1/8" to 1/4" diameter, flakes then in most cases it stayed high and enjoyed the ride till the velocity reduced to where Au's SG could take over (aka - lazy gold) and likely it has already been postulated its under the logs and all that gravel.

You have commented that you've used a metal detector to locate tramp metal along the stream and along with that 'heavy metal' you've found some gold. What size was the gold and where along the creek did you find it? Or asking a different question, what made it drop there? Gold will react to any obstructions along the stream bed, rock out cropping's, log jams, bends in the stream, large boulders and 'all the typical suspects even under extreme conditions. Larger heavier particles fall out first IF they exist in any given water channel. You've one dickens of a research project there. Floating Logs damage standing trees and leave signs of damage, busted limbs, scars where bark was broken off and such signs. Where there are no longer signs of damage to the existing trees is where I'd take a check see with my ole electronic metal detector buddy and then back down stream a ways cause that's where the velocity could have changed with logs flailing around hitting side walls and standing timber. After that it was total chaos.

Of course, I'm just guessing. Best of luck with finding clues to the puzzle................63bkpkr

 

[Goodyguy]

Seems the creek experienced a flash flood "boil box" event where all material was tumbled and tossed around, by, and into the flow.

With such events the heavies would have been deposited helter skelter along the creek anywhere they could find a low enough pressure area to fall out of suspension and become lodged/trapped.

Trouble with those type scenarios is that with so much material in the flow the larger the gold is the deeper it usually gets buried by progressively lighter and lighter material falling out of suspension on top of it as the flow subsides.

The smaller the gold the more scattered it will be but on the bright side it will be found closer to the surface.
Trying to find a concentration or pay streak is always daunting, But stick with the "gold is lazy" rule and remember that "gold is where you find it" other than that, following 63bkpkr's words of wisdom and the other solid advice posted above his will keep you on the right path.

The only things I would add is don't forget to look along the bank where erosion may have exposed gold trapped in the gravels from older flood events.

Also those flatter areas with the alluvium deposits are natural low pressure areas not to be overlooked for flood gold.
Test panning is key when looking for those elusive concentrated deposits.

As far as those unsorted deposits of material is concerned I would probably leave those for last as they are the most labor intensive as well as least likely to contain a concentration.

The other thing I noticed was all the sharp angular gangue covering the area. To me it looks like blast tailings that were washed into the creek by the flood. What a mess! Very hard stuff to deal with. You definitely have your work cut out for you.

If it were me (being almost as lazy as gold) I would probably first try to cherry pick the area with a metal detector looking for older more rounded cobble higher up the bank around exposed benches where nuggets may be found

Go for the Gold
GG~

 

[Jeff95531]

Just my unqualified 2 cents but in pic 3, I would test the gravels in front of the log jam and in low spots. Wood floats and that appears to be a drop zone. That said, gold being heavier, it should have rested shallower, upstream and in big rocks/gravel. That's where I would sample and not more than 6 or so inches deep till I found some. Good Luck! I''d like to have a problem like that!

BTW, good to see you back GG. You've been missed.

 

[goldenIrishman]

Man what an equation for "Chaos Theory" that is! There are so many variable factors that would be constantly changing from moment to moment I think the equation would drive a CRAY computer into an electronic stroke! I shudder to think of what it would take to program a problem like that into a computer.

 

[Hoser John]

In that horrendous mess god only knows. It needs much heavy water action to stratify and create pay streaks -John

 

[kcm]

... or a REALLY big shovel!!

 

[Ragnor]

I have found a few wires on bedrock at the head of the pile, just below the waterfall. Mostly, I focus my efforts up stream in the few small flatter areas I described. I figure if i move enough material I have to find a good concentrated pocket somewhere. So far though it's a wire here and a little nugget there, but I know it's like that till you find one of them sweet, sweet, honey holes. I know there is one up there somewhere and I also know larger nuggets have been found.

 

[63bkpkr]

Ragnor,
The new pictures are great and I see your point about being tough to walk around. The typical places still apply but as Terry has found, look up higher away from the stream bed for spots that could cause the gold to drop out. That is a place that could keep a person busy for a very long time. Search with your eyes and brain and then the detector and sample pan. There are Soooo many possibilities there for the heavies to drop so search, think and try! I would think that classifying would be important to reduce some of the work, a classifying setup that is light and easy to carry: metal screening that has been used to make letter holders or drawer dividers or something with larger holes like perforated vegetable BBQ holders - anything that is small/light/easy to carry and does not easily get hung up on all the brush and exposed roots. Also, a very solid hiking staff can be important in a place as rough as that one is as well as solid ankle protection to help keep from spraining the ankles or banging them up. Please keep us posted with your adventure!................63bkpkr

 

[OwenT]

Are those pictures of the main creek in your area? I didn't realize it's so small.

 

[HeavyMetalThunder]

I would be most curious as to what's in those pieces of culvert!

 

[Ragnor]

Are those pictures of the main creek in your area? I didn't realize it's so small.

This is one of a half dozen feeder creeks that drain the main ore body and enter the main tributary of the main creek in my area. I'm a couple thousand feet above my claim at this location. The snow melt is still going pretty strong up higher. I can't work any of the real good spots on my claim yet, the water is too high. I've heard rumors of large nuggets in that stream so Ive been putting my time in there untill I can work down below. It also allows me to familiarize myself with the 6 basic vein types for my area as described in the minerization report I borrowed from WSU. Small shallow pockets are described as the most likely valuable deposits in the area and I would sure like to find one that wasn't identified in the old days. The problem is even with landsat images the terrain is so steep and there is so much ground cover for a mere mortal "modern" human exploring those hills is a very extreme task. I'm thinking of buying one of those big old russian "deep' detectors once i have the money. I'm also looking for an in shape and realiable young man to assist me, but that is harder to find than gold these days. I just need a 20 year younger version of myself for that work, lol.

The main creek in my area is almost a river at this time of year. Current stream flow is 1440 cfs, I need it down around 700 to start to get at the good stuff. The gold down below is 'mostly' all flat and tumbled. There is allot more of it down there, But I really do like these crystalline pieces i find right up on the ore body.

 

[Ragnor]

I would be most curious as to what's in those pieces of culvert!

It has crossed my mind once or twice. Ive have already 'ice squirelled' a large hunk of impressive ore out of the log jam. The log jam is very unstable and with my tendancy to get injured doing 'extreme' things I have avoided climbing back down there as of yet. I would hate to remove the one sparkly rock that is holding the whole pile up, lol.



If unfamiliar with the ice squirell and his nut collecting check out the animated movie iceage.

 

[OwenT]

I'd apply for the part of the reliable and in shape young man but I'll be leaving the country soon . The squirrels name is scrat, some of those cartoons are hilarious, good thing your analogy wasn't complete and didn't involve the entire logjam coming down on you like I'm sure would happen with scrat *knock on wood*.

 

[63bkpkr]

Ragnor,
Steep loose terrain is tough and dangerous to work and I'm sure you've noted that slipping and falling is a constant variable on such ground. I've stepped onto a few similar spots in my time so far and they are "tricky". Lanny also talks about such tricky ground and has had his share of mis-steps on it. Still, the area looks super neat to play in!! Do it safely...................63bkpkr

 

[bedrock bubba]

Me, being a lazy miner, I like the lazy gold theory. I always seek out the easy gold first!

 

[cactusman]

Find out where heavy stuff dropped out, typically when the flow slowed down for any reason. Check those spots -- they may be up high, they might be right in the middle. This is where prospecting begins! Good luck -- I'm sure you will find some great pockets.