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.
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