Rich Gold Veins Can Form Rapidly
A long-standing mystery about the origin of “bonanza-type” gold deposits is closer to a solution.
Gold is a precious metal that humans have coveted since the beginning. Wars have been fought over gold, and men have searched far and wide, digging and sluicing and panning relentlessly for the nuggets that could make them rich. Kings and queens display their riches with gold crowns and jewels, lavishing gold in their palaces. Gold comprises the investments of some individuals, and the currency of some nations. Because it is malleable and can be melted, sculptors, jewelers and calligraphers use gold for exquisite works of art. Our memories readily recall images of gold rush days in California and Alaska, the desert prospector with his burro holding up that lucky nugget (or fool’s gold), and towns springing up overnight where some new bonanza mine has been discovered, only to learn sometimes that the mine was a bust, leaving dusty ghost towns in their wake.
But why should there be any gold on the earth’s surface? Gold (atomic number 79) is a heavy element, mostly inert, that should have sunk to the core of a molten planet. How did it get enriched in the rare “bonanza-type” deposits? A leading explanation is hydrothermal vents. Gold, molten in solution, somehow makes it up as much as 1,500 meters from the deep in the crust. That, however, should not happen, say five geologists from McGill University in Canada:
- McLeish et al., “Colloidal transport and flocculation are the cause of the hyperenrichment of gold in nature,” PNAS May 18, 2021 118 (20) e2100689118; DOI: 10.1073/pnas.2100689118.
Aqueous complexation has long been considered the only viable means of transporting gold to depositional sites in hydrothermal ore-forming systems. A major weakness of this hypothesis is that it cannot readily explain the formation of ultrahigh-grade gold veins. This is a consequence of the relatively low gold concentrations typical of ore fluids (tens of parts per billion [ppb]) and the fact that these “bonanza” veins can contain weight-percent levels of gold in some epithermal [i.e., above the heat source] and orogenic [i.e., mountain-building] deposits.
Their solution is flocculation: microscopic particles of precipitated gold “flocculate” or bundle up into larger particles. They studied a particularly rich gold deposit named Brucejack in British Columbia, Canada, and proposed this hypothesis:
We submit, here, a model for the colloidal precipitation, transport, and deposition of electrum, which accounts for the extreme concentrations of gold in quartz-carbonate veins at Brucejack. In this model, electrum colloids form in response to boiling of a hydrothermal fluid and are then mechanically transported to sites where they mix with seawater and flocculate. More specifically, the model involves vigorous boiling in response to strong decompression in the porphyry environment and ascent of the fluids to the shallow crustal level of the Brucejack deposit [≤1,000 m depth] where boiling continued and there was mixing with seawater. The boiling-induced rapid cooling and increases in pH and fO2 caused extreme supersaturation of gold and the formation of colloidal particles. … This flocculation at numerous, spatially discrete sites spread throughout the deposit led to the localized clogging of fluid pathways (veins) with massive but sporadically distributed clots of electrum, causing the localized hyperenrichment of gold in the deposit. Seismic pumping resulting from episodic, earthquake-related fault fracturing evidenced by crack-and-fill textures in the multistage mineralized veins and hydrothermal breccias at Brucejack, likely helped to circulate flocculated electrum particles through the deposit. By repeatedly clogging the fractures with electrum (as illustrated in Fig. 1B) then unclogging them and introducing new particles, this seismic pumping progressively converted the fractures into hyperenriched gold veins and was the final and critical driver of bonanza gold ore formation at Brucejack.
If their hypothesis holds, it sounds like a series of fortuitous geological circumstances are required to “lift” gold to the crustal surface and concentrate it as is sometimes found. And thus, a heavy element is driven by independent physical forces to our grasp: enough to be useful to man, but rare enough to make it valuable.
The authors do not indicate that it requires a long time, like millions of years; they speak of “rapid” cooling, and two of their references speak of “rapid” processes, such as the “rapid formation of a giant ore deposit.” The rapid formation of concentrated gold deposits recalls the ascent of another precious material: diamond. These gems, forged far below the crust, are shot up to the surface in violent eruptions called kimberlites.
See also our earlier articles about gold deposits:
- Gold Can Form in a Geological Instant (15 Oct 2006)
- Rapid, Plentiful Gold Possible (20 Oct 2015)
- Where Do Gems and Precious Metals Come From? (13 April 2019)
Also thought-provoking is the possibility that gold may have some limited biological function (and not just as fillings in teeth). See “Does Gold Have a Purpose? at Evolution News.
Gold is mentioned 433 times in the Bible. Clearly this mineral has had a major impact on world history. It suggests that God intended for this metal—and other precious elements and minerals—to be available to man. Animals do not mine gold; only humans do. Our Creator, knowing that we are made in the image of God, would realize that humans have creative instincts. Humans find uses for things that are not biologically essential, but important for art and culture. Moses told the Israelites that the Promised Land was “a land in which you will eat bread without scarcity, in which you will lack nothing, a land whose stones are iron, and out of whose hills you can dig copper.” Only humans care about obtaining those elements.
The Bible also speaks well of gold as a symbol of purity and value. Its beauty is so attractive, it will be a major component in the New Jerusalem in heaven. If God values gold as one of his creations, and will adorn heaven with it, surely he would have made it available to the crown of his creation, humanity. This suggests that He knew how to get it to the earth’s surface where, according to secular scientists, it shouldn’t exist. That is also why all the other elements vital to our bodies are found in the right concentrations on the surface of this Privileged Planet, made for a Privileged Species. Have you thanked your Maker for the beauty of gold?