Help Needed - Geological relationship between, hot springs, pyrite, and gold

[greeno1645]

Greetings Everyone! New to the group, but I've always have had a bug for adventure and treasure hunting. Any geologists out there that might lend their expertise with regards to some questions I have on gold prospecting?

I use to run eco-tours in the Peruvian Amazon and later did some serious exploring on the border of Brazil and Peru (from 1997-2011). The mountains that seperate Brazil from Peru (Sierra Divisor) are extremely geothermic, thousands of hot springs and sulfer springs.

I had read that gold is brought to the surface through hot springs, along with pyrite. Is this true? If so, how?

I have no real experience at gold panning, but nevertheless I tried panning in a few spots. Without exaggeration, in a few hours I panned out handfuls of pyrite and plenty of black sand with 'shiny gold' flecks, but with so much pyrite in the area, I simply discarded the black sand assuming it was of no real value.

In hindsight, I have learned that I may have thrown away actual gold, so I am considering another trip to try my hand, but would like to get a bit better educated on where/how to pan.

If hot/sulfur springs are the source of the gold, should I dig as close as possible to the springs?

There are also gravel bed/sand bars in the the middle of the streams and embankments on the edges of the streams. Is one better than the other with regards to digging around?

Is gold and pyrite always found together? If so, what do you think is the typical ratio between the quantity of pyrite found for every ounce of gold?

I know that gold sinks further down in the ground than pyrite due to its density, but how much deeper down should I expect to dig?

With regards to seperating gold from black sand....what can I use other than mercury?

Thanks for the help!

 

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[Terry Soloman]

There are a lot of variables, and it would be impossible to try and teach them to you in this thread. The short answer is, maybe. Pyrite and magnatite can mean gold and silver, then again, it could just be large amounts of other minerals and black sands with only micro gold. Read up on geothermal deposits here https://pangea.stanford.edu/ERE/pdf/IGAstandard/EGC/szeged/I-5-01.pdf When it comes to seperation chemicals, they are all nasty. Better off just pannig it out unless you are doing tons of material.

 

[smokeythecat]

I've collected minerals since forever and have researched gold deposits in the US. The following are some generalities. Gold is brought up from deep underground as part of igneous or metamorphic rock solution "melts". That is, the magma in certain areas has gold in liquid form. It comes up to the surface and cools and gets deposited in the host rock. Over time, the gold weathers out (sometimes like in California it is still in situ- in the original matrix), anyhow it weathers out, and being heavy, settles in creek and river beds among other places. Hydrothermal areas also can bring gold up from the depths, I'm pretty sure this is the less common means of depositation. At Yellowstone for instance, I'm to understand there is gold found nearby, in igneous materials, but it is not actively being brought up to the surface by the geysers. Gold may or may not associated with pyrite, with is a compound of iron and sulfur. Black sand is usually an iron mineral, so swirling a magnet in the black sand will get rid of a lot of it. It will stick to the magnet. Rutile is also a very common "black sand". It is the ore of titanium and will not be attracted to a magnet. You might try crushing the pyrite and panning the gold out. I wouldn't use mercury due to its toxicity. In the US, there are gold deposits in New England, primarily in Maine and New Hampshire with glaciated gold in Mass, and Connecticut. New York has gold brought in by glaciers. Pennsylvania has both glaciated gold in the northern counties and deposit gold in Lancaster, Dauphin and York Counties. New Jersey has native gold from Franklin, in Sussex County, but it is microscopic and comes of the iron/lead/zinc ores from there. Maryland, Virginia, North and South Carolina and Georgia have all had commercially worked gold deposits over the years. There is some gold in Tennessee near the NC border. Sporadic glacial gold is found in some of the midwest states and northern Alabama has some small gold. In the west, Alaska, California, Oregon, Washington and Arizona have deposits as well as most of the other western states. The Dakotas still have some huge working mines. Canada still has huge gold reserves. Best advice is to research your area thoroughtly to see what the history is and go from there.

 

[greeno1645]

Thanks. So, it seems impossible to know for sure if the springs are carrying gold or not without what appears to be a fairly complicated test using titanium cores, so perhaps it is best to leave that part of my question unaswered (for the time being).

Can you offer some insight on how you might approach prospecting in this area? Your experience would be very helpful.

Where would you dig first? Close to the spring, gravel/sand beds in the middle of the stream near snags/rocks, or the stream embankments near high water marks? How deep should I dig? There are also a number of natural pot holes through the stream systems, but I do not think backpacking a dredge into the jungle would be much fun.

Most of the surrounding stone is sedimentary, so the stream beds are covered in sand with underlying and exposed bedrock throughout. The embankments are high in clay and sediment. Any of this make any difference on where you might dig?

In my one and only attempt at prospecting, I processed about 5 5-gallon buckets of material from an embankment. From this, I accumulated about 50 pyrite nuggets (nicely rounded/polished from the river water) ranging in size from about 1/2 inch to 1 1/2 inch in length - we had countless smaller nuggets of pyrite which we discarded. As for black sand, I don't remember exactly, but I am sure I filled 1 whole snuffer bottle full, but for some reason, I kind of remember filling 2 bottles.

Would this be considered a high, average, or low concentration of minerals? Would I want to look for a spot with lower concentrations of pyrite, or higher?

Thanks again.
Tim

 

[TerryC]

Yes, hot springs DO bring up gold in the hot springs! Even the foliage around hot springs are covered with gold from the dissipation of the venting of the spring. Which means as we speak, gold is being brought up from below to be deposited (in solution) above ground! Read this PDF file for some enlightening info!... http://www.cbmap.net/images/nelson-gold-in-the-hot-spring-environment.pdf TTC

 

[greeno1645]

Thanks! I just finished reading the article.... It seems that hot springs that have a high volume of water flow and sulfur produce more gold. Did I understand the article correctly? If so, that is a very good indication that the springs in the area I travel are capable of being gold producing - these springs have significant flow to the point they create a river of hot water 10 meters wide at some parts.
So, where do you think is the best place to dig? Right next to the spring?

 

[TerryC]

I got at least two things out of the file. First, the amounts of gold are very small and second, the gold is locked up in solution. Digging would prove futile since the article seems to infer that the gold has only been found in 10 (I think) springs so far. I believe it also compares it to gold like the Carlin Trend, doesn't it? TTC