Rapid, Plentiful Gold Possible

Geologists have up-estimated the process of gold ore transportation from deep underground to surface by a factor of ten to a hundred.

French geologists and mineralogists have reason to believe gold is much more plentiful on Earth than expected. Their paper in PNAS shares the news that trisulfur ion S₃^– is very stable at high temperatures and pressures, and has the ability to form “very stable and soluble complexes” with gold ions in solution, transporting them rapidly to the surface.

These species enable extraction, transport, and focused precipitation of gold by sulfur-rich fluids 10–100 times more efficiently than sulfide and chloride only. As a result, S₃⁻ exerts an important control on the source, concentration, and distribution of gold in its major economic deposits from magmatic, hydrothermal, and metamorphic settings. The growth and decay of S₃− during the fluid generation and evolution is one of the key factors that determine the fate of gold in the lithosphere.

Other geologists have assumed that only hydrogen sulfide and chloride ions are capable of forming complexes with aurous gold ions. They haven’t considered the role of trisulfide ion significant because it breaks down rapidly when it cools, and up till now, experiments to test its solubility with gold at such high temperatures and pressures were unavailable. This team believes that the presence of this ion is highly likely to be plentiful in typical magmatic and metamorphic environments from as far down as 10 km, where high pressure, high-temperature conditions exist. Then it could be transported by hydrothermal springs and magmas in large quantities to the upper crust and surface of the Earth.

The existence of gold–trisulfur ion species with large capacities to extract, transfer, and precipitate gold reduces these requirements and shortens by up to 10–100 times the duration needed to form a given deposit from a much smaller magma or rock source. Consequently, the choice of possible locations where new deposits may be found is significantly extended, both in time and space, thus offering more potential for exploration. The finding of sulfur radicals concentrating gold at depth suggests that huge, so far unknown deposits still await discovery. This conclusion agrees with recent estimations of economic gold resources to a depth of only 3 km of Earth’s continental crust, which are ∼40 times larger than gold reserves in currently known deposits.

Make you want to go prospecting? Don’t put too much on the market at once, or you will drive the price down.

It’s really quite incredible how many elements and minerals of value and usefulness (and beauty) to humans are transported to the surface from deep within the Earth by curious convocations of independent geochemical processes. The authors describe gold “mobilization” by concentration and precipitation. To make this work, there have to be ions that can bind to gold. Then, the temperatures and pressures have to be right. But if it sits 10 km down, nobody can reach it. Along come hydrothermal vents and magmas to transport it to the cooler surface, where it precipitates out into gold ore where it can be mined or found in streams.

On top of all that coincidence, gold is beautiful: shiny, malleable, and perfect for creative artwork and ornamentation. Similarly improbable processes conspire to bring diamonds from deep in the mantle to the surface by rapid eruptions in kimberlite dikes. Almost makes you sense a divine plan to make our planet not only habitable but useful.  Gold is not needed in the human body (perhaps in the occasional tooth filling) but it sure had a lot to do with human history! Now we find out there may be plenty to go around if we just know where to look. I wonder if any 49er’s or Alaska gold rush fortune hunters left deposits that were closer to home and easier to get to.

The suggestion of a divine plan in this gold transport system is reinforced by the second chapter of the Bible:

A river flowed out of Eden to water the garden, and there it divided and became four rivers.  The name of the first is the Pishon. It is the one that flowed around the whole land of Havilah, where there is gold.  And the gold of that land is good; bdellium and onyx stone are there. (Genesis 2:10-12)

Did the springs that watered the ground from underground reservoirs also transport gold to these rivers? Since this was still part of the original creation God declared to be “very good,” we can assume that beautiful elements and minerals were created for His glory and our delight. It’s possible that gold was more plentiful in the early Earth than it was after the Flood; we don’t know. We’re just glad that God’s mobilization and transportation system still works.  Now we learn it works better than geologists thought.