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Studying rough inclusions can not only lead to new kimberlite sources, but also help scientists learn about the planet.
Oct 3, 2019 5:33 AM   By Leah Meirovich
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Academics have long been working to uncover the earth’s mysteries and to answer questions relating to its deepest-held secrets. Through a range of partnerships with diamond labs and mining companies, scientists are filling in those blanks for questions such as how the oldest continents formed or what the earth’s mantle consists of. At the same time, they are providing useful information that could change the face of diamond exploration.

“Diamonds and their pristine mineral inclusions are a virtual window into the earth’s mantle, providing crucial information about the geological evolution of our planet,” says Fabrizio Nestola, head of the department of geosciences at the University of Padova in Italy. “Their investigation provides several key answers to geological mysteries.”

Nestola and his diamond-research team — which consists of a second professor, a senior research fellowship student and two PhD students — have collaborated with the Gemological Institute of America (GIA) on several projects, including studying blue diamonds to determine where they get their color. They began working together in 2016, when the GIA sought a research partner on the study of super-deep diamonds that form between 300 and 1,000 kilometers below ground. The department receives a variety of grants and endowments from private and government foundations, as well as from the school itself. However, Nestola notes, most of the projects the department works on are ideas he puts forward.

Common interests

For researchers at Canada’s University of Alberta, participating in diamond studies is a two-way street.

“We approach companies with ideas, and they approach us,” says Thomas Stachel, one of the founders of the university’s Diamond Exploration and Research Training School (DERTS).

“Diamond research is so exciting, because it has both economic relevance and profound impact on basic research, with key contributions to the understanding of the formation of early continents and the mineralogical makeup and composition of the deep mantle,” adds Stachel, who is also Canada research chair in diamonds for the university’s Department of Earth and Atmospheric Sciences.

His team has worked with every major and almost all junior companies conducting diamond exploration in North America, including De Beers, Rio Tinto and Dominion Diamond Mines, as well as with the GIA.

To date, DERTS — which consists of seven faculty members, several postdoctoral researchers and 15 graduate students — has received more than $30 million in research grants and funding from the university, the Canadian government and private groups. While De Beers has also contributed funding to the group, many of its collaborations with mining companies are solely for the benefit of information. These projects generally run from six months to four years, but can last as long as 10.

Findings that go deep

Among other things, members of DERTS have been involved in pinpointing the age of mineral inclusions inside diamonds, when and how those diamonds formed, and establishing that they are not, in fact, created inside lava.

“The key initial conclusions from the very first dating studies were the establishment that a diamond is genetically unrelated to the kimberlite magma that brings it to the surface, simply because it is billions of years older,” Stachel explains.

This knowledge helps miners understand what to look for when launching exploration programs, and to think outside the box and consider areas that would generally be deemed unconventional for hosting diamond veins. Previous data seemed to suggest that diamond deposits were found in portions of the earth dating back more than 2.5 billion years, such as in South Africa’s Archean Kaapvaal Craton, while other, newer areas were barren. However, a recent collaboration between the University of Alberta and De Beers proved that this was not the case, and that Proterozoic crust (between 541 million and 2.5 billion years old) can also host viable primary diamond deposits.

The DERTS team sampled stones from the Victor mine in Ontario, Canada, and found that lherzolite, a peridotitic rock that had previously been ruled out as an indicator for diamonds, was present in a predominant portion of those stones. It was then compared to stones from other Canadian areas, such as Buffalo Head Hills and Saskatchewan, as well as mining sites in Western Australia and South Africa. Not only did the group prove that diamonds could be found in an area previously considered unfertile, but the discovery of a new indicator for diamond formation could help geologists locate and identify new valuable deposits around the world.

“The outcome of the project fundamentally changes our understanding of where diamonds come from,” Stachel observes. “It has the potential to cause diamond companies to retool their approach to exploration.”

Academic edge

For its part, the GIA says that while it has some of the top researchers in the field, as well as access to numerous diamonds from areas around the world, it still benefits from partnering with universities.

“When working on advanced research projects, we collaborate with researchers who are affiliated with different universities as a way to share expertise and work toward a common goal,” explains Tom Moses, the GIA’s executive vice president and chief laboratory and research officer.

While Moses acknowledges that his institute, the miners and the universities all enter into a project with different interests in mind, everyone gains from the result. For scientists, he elaborates, “diamonds are a combination of gemological and geologic science that provide a window into the earth’s core” and deliver “clues to the early history of our planet.” For the GIA, “the main focus and mission behind our research is always to stay in the forefront with advances in diamonds and gemstones to ensure the public trust in gems and jewelry.”

Many of the research projects also come about naturally, as one answer can often raise more questions. Stachel’s newest project, working with Rio Tinto and Star Diamonds to study stones from the Fort à la Corne site in Saskatchewan, is a logical next step in the lherzolite research, as that deposit is also set in Proterozoic crust, and results could further confirm the group’s theory.

Meanwhile, studying super-deep diamonds led to Nestola’s interest in finding stones containing inclusions such as wadsleyite and bridgmanite. These minerals are found near the lower mantle but have yet to appear closer to the earth’s crust, since they transform into different minerals as they rise to the surface.

And while both scientists and miners aim to contribute as much to the future of mining as possible, the academics’ main focus is clear.

“We are scientists,” Stachel says. “We love to work with the diamond industry and to support its growth, but our primary motivation is scientific knowledge. Understanding the exact process[es] of a diamond is the holy grail.”

Images: Shutterstock
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