Think gold veins take a long time to form? Think again!

[UncleMatt]

Hey All, I saw this article and thought everyone might find it interesting. It never occurred to me before that fissures with mineral laden water under very high pressure that experience a rapid drop in pressure might form mineral veins in a very short period of time.

Earthquakes make gold veins in an instant | Geology IN

 

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[Duckshot]

How does superheated water put gold into solution?

Oh, you are saying the gold in solution displaces the superheated water already in the fissure?

Where did the gold come from?

 

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[cyberdan]

...I'm not certain, but the amounts of gold dissolved in seawater would be fairly low.

Now take this with a grain of salt (pun intended) I pulled this quote from a noaa.gov website

"Each liter of seawater contains, on average, about 13 billionths of a gram of gold."

So if my math is correct you would have to process 404,300,000,000 liters (or 106,804,760,768 gallons for all us Americans) of seawater to get one ounce of gold. In other words you would need to drain 161,720 olympic size pools to get that ounce.

 

[cyberdan]

I did a little research on seawater composition. I do not see why everyone wants to try to pull gold out of seawater when there are many more metals that are a lot more abundant than gold. Try pulling all of these and at the same time and it might be profitable: magnesium, aluminium, lithium, copper, zinc, manganese, lead, uranium, mercury, silver and platinum.

 

[Clay Diggins]

Superheated water does not put gold into solution. As stated before chlorine (a halogen) is usually the element that allows gold to go into solution. This happens even at room temperature although it does happen more rapidly when energy, in the form of heat, is applied to the Gold and Chlorine.

Gold tends to be concentrated in the vapor phase of fluids at high temperatures and pressures. The gold is dissolved out of the mass of rock and concentrated in solution by the chemistry - not the heat or pressure. The heat and pressure do help the gold/chloride solution reach a supersaturated state but the heat and pressure are not the cause of the solution. Often Silicon, Sulfur, Iron and another metals are present and an important part of the chemistry of these solution/deposition cycles. These are never pure Gold Chloride solutions.

This is really about chemistry. The energy supplied by heat and pressure help keep these saturated solutions moving within the rock mass. The heat and pressure are the energy source, much like gas in a car. The chemistry is what creates the saturated solutions and ultimately the mineral deposits - they are the engine and wheels.

Take away the gas and you still have a car you can roll and steer it and even live in. Take away the engine and wheels and you have a can of gas - no car. Same thing with mineral chemistry - take away the heat and energy and you still have minerals in rock. Take away the rock and you have hot air - no gold.

When dealing with heat energy it's important to remember that in a closed system, like you will find at depth in the mantle, the heat/pressure have to observe natural laws. The first law of heat in a closed system is accounted for in the first law of thermodynamics. Here's a brief version that only sketches out the beginning rules for a very complex subject.

Energy can be neither created nor destroyed. However, energy can change forms, and energy can flow from one place to another. A particular consequence of the law of conservation of energy is that the total energy of an isolated system does not change.

In other words all forms of energy transfer be they heat or work have to be accounted for. Nothing just disappears from the system.

When it comes to heat it's important to understand that heat energy only moves from higher energy states (hot) to lower energy states (cold).

Heating is a natural process of moving energy to or from a system other than by work or the transfer of matter. Direct passage of heat is only from a hotter to a colder system.

So the gold (and other elements) are dissolved out of the rock and concentrated in semi liquid solutions by chemistry. Transfers of energy like heat and pressure changes can cause that solution to supersaturate or change state from a liquid/vapor to a solid and back again. Similar to ice melting and refreezing. Changes in chemistry can do the same thing with or without heat/pressure. Like adding salt to ice can cause it to melt even in freezing temperatures. When those solutions change state to a solid and maintain that state sometimes they form concentrated ore bodies worth mining. And that's where the prospector comes into the equation. With some work, and often some chemistry, prospectors can find and mine those now solid solution deposits.

It's still out there - go get u sum!

Heavy Pans

 

[delnorter]

A thing of beauty Barry. I even looked up the tree laws of thermodynamics to re-read them. Oh ya, there's a zeroth law as well, so I guess that makes 4 laws.

Mike

 

[augoldminer]

as a gold miner for many years and after taking collage prospecting courses

i will have to say that the research paper does not cover all the ways gold forms in veins.

gold forms under three cases.

drop in pressure drop in temperature and change in PH.

and it does not travel in water very often.
in many cases it formed in a gel solution traveling up the vein

Ihe last mine i worked it formed in a change in PH as the vein went through a dike of carbonaceous Serpentine. and would disappear
above pinch points as the temperature changed.

If the gold is found in large Quartz crystal areas known as water course vugs it formed slowly.

in mines it take a lot of research to tell how the gold formed in the veins.

https://www.911metallurgist.com/blog/classification-of-gold-deposits-auriferous.

knowing how the gold formed tells you where the gold will be in the vein

you have hydro-thermal. mesa-thermal, stockwork, epithermal, replacement

 

[Clay Diggins]

Good points augoldminer. So often these articles are simplifications of a basic well known principle of deposition and when taken alone they can seem to be great revelations of how gold is concentrated and deposited when it fact they are a small part of the whole picture. As long as we keep that in mind when studying these papers we can eventually get a grasp of the bigger picture.

For those of you enjoying this subject and interested in learning more you don't have to be a scientist. The materials are out there and although the subject is complex understanding some of the basics can really help in understanding where you might find concentrations of gold in the several different types of deposits.

Here are a few more complex articles that cover a much broader range of mineralization types. They aren't the final answer but they can be a springboard to a deeper understanding of how different deposit types occur.

Starting with this Encyclopedia Britannica article on hydrothermal deposits can help with understanding the general mechanisms involved with forming and moving concentrated mineral solutions into place. The second paragraph alone will help you understand how simplified the discussion involved in the original post article was.

Hydrothermal deposits are never formed from pure water, because pure water is a poor solvent of most ore minerals. Rather, they are formed by hot brines, making it more appropriate to refer to them as products of hydrothermal solutions. Brines, and especially sodium-calcium chloride brines, are effective solvents of many sulfide and oxide ore minerals, and they are even capable of dissolving and transporting native metals such as gold and silver.

That paragraph alone is a better explanation of the nature of hydrothermal fluids than most others you will read. Simple and to the point.

That article is very simplified but it does cover the fact that there are many chemical and mechanical processes involved in even a simplified model of mineral enrichment and deposition.

Here is another slightly more advanced article that delves a little deeper into the chemical aspects of gold enrichment and deposition. It's not very long and if you want you can download it as a free PDF to put in your library.

Don't let the science words put you off they are just like our ordinary way of speaking but they are a sort of science shorthand to save explaining things that someone familiar with the subject will already know.

You can be one of those knowledgeable readers by just looking up the words you don't already know the meaning of.

For instance "meteoric water" doesn't have anything to do with rocks falling out of the sky but is just a shorthand way of saying the water came down from the surface of the earth. Most water in most hydrothermal solutions didn't come directly from the surface so discussions about hydrothermal solutions need to make that distinction. Now I hope you will be wondering just where all that water did come from if it wasn't from the surface. The answer may surprise you and once you understand where that water comes from you will have a much better understanding of how this whole process works.

It will be helpful when reading this article to know that fugacity is a measure of the tendency of a gas to escape or expand. It's not a real world thing but a way of understanding how gasses "fizz" under less than pure or ideal conditions. Science shorthand for what happens when you open a carbonated drink - sort of.

You will get hints from both these articles about why particular mineral associations are linked to different deposit types. The surrounding rock has as much to do with where and how gold deposits form as the composition of the hydrothermal fluid does.

This is all about chemistry and the real action takes place where two different chemical types interact. That's why augoldminer is pointing you to things like wall rock and pH gradients. Those are the things that matter to the successful prospector. If you understand the chemistry and mechanics of gold deposits you can learn to walk right by the nonproductive mineralization signs and concentrate on the mineralizations that produce free gold that you can actually mine yourself. At the same time you will learn that other mechanisms of mineralization can be very profitable discoveries even though you personally can't profitably mine a Carlin type deposit or a disseminated Antimony/Gold deposit.

If you study this stuff the next time you encounter a mineralized "vein" you will have a much better idea of whether it's just interesting or possibly a valuable deposit. You will have a better idea of which side of a dike or intrusion you are more likely to find free gold on. In short by understanding the basics of mineralization you will have much more productive prospecting time and be better able to know which mineral areas are more likely to be productive before you put boots on the ground.

Heavy Pans

 

[Miner 49er]

You make alot of sense I have been mining a lead as big as my thumb for the last two seasons and thats how I found it, all the mineralized iron that runs with it almost blew my detector out of my hands. Thanks for validating my thinking.

 

[UncleMatt]

This article obviously never intended to cover every aspect of hydrothermal mineral deposits, it was intended to illustrate that earthquakes can cause rapid formation of mineral veins when they enlarge or rupture fissure systems with mineral rich water flowing in them. Of course, Clay's comment are always appreciated and educational.