Hexbyte Glen Cove Clues from soured milk reveal how gold veins form thumbnail

Hexbyte Glen Cove Clues from soured milk reveal how gold veins form

Hexbyte Glen Cove

McGill Colloidal Au research team study a mineralized (gold-bearing) vein underground at the Brucejack mine. Credit: Duncan McLeish

For decades scientists have been puzzled by the formation of rare hyper-enriched gold deposits in places like Ballarat in Australia, Serra Palada in Brazil, and Red Lake in Ontario. While such deposits typically form over tens to hundreds of thousands of years, these “ultrahigh-grade” deposits can form in years, month, or even days. So how do they form so quickly?

Studying examples of these deposits from the Brucejack Mine in northwestern British Columbia, McGill Professor Anthony Williams-Jones of the Department of Earth and Planetary Sciences and Ph.D. student Duncan McLeish have discovered that these gold deposits form much like soured milk. When milk goes sour, the butterfat particles clump together to form a jelly.

Q&A with Anthony Williams-Jones and Duncan McLeish

What did you set to find out?

Scientists have long known that gold deposits form when hot water flows through rocks, dissolving minute amounts of gold and concentrating it in cracks in the Earth’s crust at levels invisible to the naked eye. In rare cases, the cracks are transformed into veins of solid gold centimetres thick. But how do fluids with such low concentrations of gold produce rare ultrahigh-grade gold deposits?

What did you discover?

Our findings solve the paradox of “ultrahigh-grade” or “bonanza” gold formation, which has frustrated scientists for over a century. The paradox of bonanza gold deposits is that there is simply not enough time for them to form, they should not exist, but they do!

McGill Professor Anthony (Willy) Williams-Jones and Pretium Resources Inc. geologist Joel Ashburner study a mineralized (gold-bearing) vein on surface at the Brucejack mine. Credit: Duncan McLeish

As the concentration of gold in hot water is very low, very large volumes of fluid need to flow through the cracks in the Earth’s crust to deposit mineable concentrations of gold. This process would require millions of years to fill a single centimetre wide crack with gold, whereas these cracks typically seal in days, months, or years.

Using a powerful electron microscope to observe particles in thin slices of rock, we discovered that bonanza gold deposits form from a fluid much like milk. Milk consists of little butterfat particles that are suspended in water because they repel each other, like the negative ends of two magnets. When the milk goes sour the surface charge breaks down, and the particles clump together to form a jelly. It is the same with gold colloids, which consist of charged nanoparticles of gold which repel each other, but when the charge breaks down, they “flocculate” to form a jelly. This jelly gets trapped in the cracks of rocks to form the ultra high-grade gold veins. The gold colloids are distinctively red and can be made in the lab, whereas solutions of dissolved gold are colourless.

Why are the results important?

We produced the first evidence for gold colloid formation and flocculation in nature and the first images of small veins of gold colloid particles and their flocculated aggregates at the nano-scale. These images document the process by which the cracks are filled with gold and, scaled up through the integration of millions of these small veins, reveal how bonanza veins are formed.

How will this discovery impact the mining industry?

Ultra-high-grade (bonanza) occurrence of gold in exploration drill core from the Brucejack mine. Credit: Pretium Resources Inc.

Our results are important to the and in Canada and around the world. Now that we finally understand how bonanza deposits form, mineral exploration companies will be able to use the results of our work to better explore for bonanza deposits as well as gold deposits. Genetic studies of Canada’s most fertile metallogenic districts—such as the one we have just completed at Brucejack—are required to improve our understanding of how world-class mineral deposits form, and thereby develop more effective strategies for their exploration.

What’s next for this research?

We suspect that the colloidal processes that operated at Brucejack and other bonanza gold systems may also have operated to form more typical . The challenge will be to find suitable material to test this hypothesis. At Brucejack, the next step will be to better understand the reasons why colloid formation and flocculation occurred on the scale observed and reconstruct the geological environment of these processes. We have also been preparing colloids in the lab in an attempt to simulate what we discovered at Brucejack.

More information:
Duncan F. McLeish et al, Colloidal transport and flocculation are the cause of the hyperenrichment of gold in nature, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2100689118

Clues from soured milk reveal how gold veins form (2021, May 21)
retrieved 22 May 2021
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Hexbyte Glen Cove Turkish lake with likely clues to Mars gains unwanted fame thumbnail

Hexbyte Glen Cove Turkish lake with likely clues to Mars gains unwanted fame

Hexbyte Glen Cove

Lake Salda in southwest Turkey is at risk after the site was picked to create more green spaces for the public

Boasting azure waters and white sands, a Turkish lake that NASA thinks hides secrets about Mars threatens to become too popular for its own good.

Lake Salda gained international renown when US scientists began poking around in preparation for the Perseverance rover mission, which has been beaming back videos from the Red Planet since February.

The Jet Propulsion Laboratory even posted a picture of the pristine lake on its site before touchdown, saying it might resemble what an “aqueous” Mars looked like billions of years ago.

Now, the 4,370-hectare (16.9-square mile) lake in Turkey’s southwest has been picked by President Recep Tayyip Erdogan as part of a project to create more green spaces for public use.

The news spells disaster for local activists and lawyers, who fear that the twin blows of NASA and Erdogan’s interest could open the floodgates to tourists.

Splashing around in its waters, the sea of humanity could destroy the very ecosystem that made the lake special in the first place, campaigners warn.

“The future of the lake is at risk if millions of people come,” said Lake Salda Preservation Association head Gazi Osman Sakar.

‘It’s alive’

The lake is most famous for the White Islands area with the brilliant sands, as well as endemic flora and fauna such as the Salda seaweed fish.

Activists fear the twin blows of NASA and development could open the floodgates to tourists at Lake Salda

There are also minerals of different origin. NASA thinks one of them, hydromagnesite, is similar to the carbonate minerals detected at Jezero Crater—a former lake on Mars that the rover is now exploring.

The hydromagnesite sediments along Lake Salda’s shoreline “are thought to have eroded from large mounds called ‘microbialites’—rocks formed with the help of microbes,” NASA said.

This all folds into the mystery about possible life on Mars, in some microbial form a very long time ago.

There are many tectonic lakes like Salda across the world.

But what makes Salda unique, geology engineer Servet Cevni said, is the lake’s transformation into a closed ecosystem with its own living mechanism.

“Because it’s alive, it’s so sensitive to outside interventions,” Cevni told AFP.

Yet that intervention is already on its way in the form of nine small buildings that have appeared near a planned People’s Garden by the lake.

Sakar said some of the white sand has already been moved from the White Islands area to another called People’s Beach for road construction.

“The project should be cancelled,” Sakar said. “The lake cannot be protected while it’s used.”

Graphic locating Lake Salda in Turkey studied by NASA scientists due to its similarity to Jezero crater on Mars, landing site of the Perseverance Rover looking for ancient signs of life.

Court battle

Swimming is forbidden at the White Islands but people are still able to take a dip in other parts.

Sakar’s association wants the lake off limits entirely for swimming to preserve its ecosystem. Instead, he proposes creating observation posts for visitors to see the lake.

“If single-cell organisms die, Salda is finished,” the engineer Cevni agreed. “Those White Islands won’t be renewed, that white structure won’t come together.”

The damage thus far can be recovered in 150 to 200 years if people do not destroy it further, Cevni said, adding: “If we do, it won’t ever recover.”

The Lake Salda Preservation Association has seen its legal bid to cancel the green spaces project rejected in court.

Sakar is appealing the ruling and also campaigning for UNESCO to put Salda on the world heritage list.

“Salda is dying,” Sakar said.

“If single-cell organisms die, Salda is finished,” warns geology engineer Servet Cevni

But campaigners are not the only ones expressing concern.

Aysel Cig, a goat-herder who lives in a village close to the lake, said things were more pleasant before Salda gained its fame.

“Our lake, our village was much cleaner three, five years ago,” she said.

Responsible tourism

But besides dirt and foreign organisms, tourists also bring cash, which the locals around Lake Salda welcome.

Suleyman Kilickan, 60, worked in a cafe with plenty of outdoor seating by the lake that employed 30 people before the coronavirus pandemic hit.

Interest in the lake rose considerably with the NASA mission, Kilickan said, noting that most of his visitors were foreigners who appeared to be respectful of the lake.

“If there’s tourism, there’s life,” Kilickan said.

“I would encourage tourism,” he said, emphasising the importance of ensuring visitors act responsibly.

Interest in Lake Salda rose considerably with the NASA mission

The environment ministry said last month it would limit the number of visitors to the White Islands area to 570,000 a year.

Nearly 1.5 million people visited the lake in 2019, and 800,000 came last year during lulls in coronavirus restrictions.

But Nazli Oral Erkan, of the Burdur Bar Association’s Environment Committee, said the proposed cap was not enough to protect the lake.

“Salda is like a natural museum,” she said.

© 2021 AFP

Turkish lake with likely clues to Mars gains unwanted fame (2021, April 28)
retrieved 29 April 2021
from https://phys.org/news/2021-04-turkish-lake-clues-mars-gains.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

Read More Hexbyte Glen Cove Educational Blog Repost With Backlinks —