Learning about our planet never seems to end. From undiscovered sea mounts to new gold deposits, there is always something new coming around the bend. As miners, we all know that gold veins form in the earth and get pushed to the surface with seismic activity but a relatively new discovery has found out how gold veins are formed along fault zones three to six mile down. When you think of it, how do gold veins form? Does liquid molten gold just squirt into any opening in rock? I can say no to that. Almost all veins are hydrothermically formed. Meaning, super-heated water carries gold and silica along for many miles under the earth’s crust. This water travels in faults and rock veins until it encounters a sheer zone. These upward bound sheer zones are the roots of moving plates that make up the Earth’s crust. It’s closer to the surface where these sheer zones become interesting. Due to the travelling nature of our Earth’s skin (crust), these sheer zones turn into much smaller fault lines and increase greatly in number.
The super-heated water is under incredible pressure and would love the chance to equalize with the surface. This mineral rich water also acts like a lubricant holding some rock surfaces away from each other. As I already mentioned, this water is held captive in faults within a couple miles of the surface. Now when pressure builds up on deeper rocky plates they will equalize with a sudden release of pressure and rapid movement. This is like shaking an apple tree. The movement of the rocky plates sends out a three dimensional shock wave. In essence, rattling any fault line that is close. The result is movement of these fault lines especially any that are active and contain water.
What we are looking for is a sudden pressure drop along any fault line that contains the super-heated mineral rich water. It takes very little movement in these fault lines for a pressure drop to occur. When this drop happens it only takes an instant for gold and silica to drop out of the watery solution. In essence, the microscopic (nano) particle gold flash settles out of solution. This happens repeatedly over hundreds and thousands of years and the deeper the fault the more time gold has to accumulate in these zones.
So here’s what happens step-by-step:
1: Super-heated water that is rich in minerals and gold slowly travels in faults and sheer zone under the Earth’s crust. (Note: a combination of heat, pressure and sulphur also acts as a low grade acid which helps hold the gold in solution).
2: The density of gold particles varies from localized aqua-duct to localized aqua-duct (aqua-ducts vary greatly in size based on depth and surround rock type).
3: As fault zones are nearer to the surface they are much more prone to sudden pressure drops with ground movement.
4: A Deep (or shallow) earthquake will take place sending out a three dimensional shock wave shaking any fault zones within range.
5: The shaking causes some movement in dissimilar rock faces resulting in a pressure drop along this zone.
6: The pressure drop causes a flash migration of gold and quartz particles onto surround rock surfaces.
7: Depending on depth and gold particle saturation, this process can go on for centuries, millennia and hundreds of thousands of years, depositing layer after layer of gold inside of a fault zone.
8: The deeper faults can grow gold to a considerable thickness whereas surface faults are usually quite thin.
9: Deep earthquakes can lift these larger gold veins right to the surface which explains why there can be some monster nuggets found from time to time. Erosion, landslides and glacial movement all work to topple chunks of gold into mountain valleys and rivers.
10: I should also mention that for deeper aqua-ducts the pressure will drop right after an earthquake but then rebuild again as the Earth’s internal heat re-establishes pressure again.
Most of the time we see the results of erosion and all these surface veins are being ground down and washed into waterways as flake gold.
When you get larger earthquakes continental subduction can occur. What that means is one large land mass plate is running under another. When this happens under the ocean, enormous volumes of water get sucked (for lack of a better word) under the other plate. This water that is now trapper gets pulled deeper and deeper under the Earth’s crust. To say it reaches boiling pint would be an understatement, try 1700 plus degrees Celsius. Now subject that water to minerals, sulphur, gold, beryl crystal particles plus a multitude of other metals and elements. It’s the heat and chemical make-up of this water that determines how much liquid gold is going to be picked up and carried along when the water and gold are exposed to each other. Silica and gold are companion particles, generally where you find one you will find the other, hence the quartz and gold formations we find when gold mining.
I mentioned sulphur; this turns the water slightly acidic which promotes suspension of gold particles. In addition, sulphur can form a chemical bond with gold which is why iron pyrite and gold can be found together. I’m not talking about visible gold although that can happen. What I’m getting at is large formations of just iron pyrite. You need to crush it and then chemically treat it with a cyanide bath or heat it to break the sulphur bond and extract the gold. This is gold at its smallest size other that nano gold. Microscopic gold particles will break loose when the pyrite is heated, allowing it to be recovered (hopefully on mass). Gold at this size level can “self-weld” together depending on purity (an article for another time). Beware not all iron pyrite will contain gold.
At the risk of being obvious, gold likes gold. As gem crystals can form simply by the law of molecular attraction, so gold will seek itself out when conditions are right. This relates right back to when gold “flash-settles” out of solution during an earthquake. This happens fairly deep underground and it is only when we get upheaval of rock masses that some of these hydrothermically formed gold veins get pushed to the surface.
In Search of the Mother Lode
When you do find a gold vein it is always disconnected from its parent source. This is normal. What actually happens is you get a deep earthquake which pushes a mass of rock and gold up to or above the surface. This condition may last for 10,000 years but sooner or later the Earth’s plates move again and the lower section of that gold vein gets pulled back down deeper into the crust, leaving the top section “high and dry” for some lucky/skilled miner to find. Even if that entire vein were left intact we are still talking about one hydrothermic vein. The Earth has thousands of these veins. Most are out of our reach 1 – 6 miles down. A few stick their head up usually in a mountain range and slowly erode with the mountain or until a passing glacier steamrolls down the mountain (Glacial Gold).
Is there a Mother Lode? Yes! I believe there are many such rich finds deeper down in the Earth with rare exceptions at shallower depths. Either way, we still have a number of undiscovered gold veins hidden in mountain ranges running parallel to hot springs as they head to the surface and a few with long lived volcanoes. If you are willing to look there is a possibility that you could find a gold vein but don’t base your life on it. Too many others have spent their lives in search of “the big find” only to come away empty handed.
So, bring a gold pan, fishing rod and some additional free time along to explore and you will see stuff 99% of other people have never laid their eyes on. If you’re ambitious you’ll have a chance to do a little mountain rock hunting and maybe find that next vein of gold. If you do find something worthwhile IMMEDIATELY stake a hardrock and placer gold claim over the area.
Most of all have fun and enjoy. Gold may be the reason we’re outside but it isn’t the purpose of life.
Hope you get nuggets.