Scientists' work improves odds of finding diamonds

Jul 14, 2010

While prospectors and geologists have been successful in finding diamonds through diligent searching, one University of Houston professor and his team's work could help improve the odds by focusing future searches in particular areas.

Kevin Burke, professor of and at UH, and his fellow researchers describe these findings in a paper titled "Diamonds Sampled by Plumes from the Core-Mantle Boundary," appearing July 15 in Nature, the weekly scientific research journal.

Burke's team found that kimberlites, which are rare that include diamonds, owe their origin to occasional pulses of hot - called mantle plumes - that have risen through the entire thickness of the Earth's mantle from deep down next to the core, or innermost part, of the planet. This core/mantle boundary lies at a depth of about 2,000 miles. While the idea there might be mantle plumes rising from the core/mantle boundary was first suggested about 40 years ago, it is only within the past few years that evidence of plumes coming all the way from this boundary to the Earth's surface has been clearly demonstrated by Burke's group.

"Our approach is new, because it combines observations of the Earth's deep interior from with evidence of how have moved about on the Earth's surface during the past 500 million years," Burke said. "I have been interested in mantle plumes from the core/mantle boundary since they were first hypothesized in 1971. About 10 years ago, I realized there might be a link between the seismically defined structure at the core/mantle boundary and volcanic rocks at the Earth's surface that had been suggested to be linked to mantle plumes. I immediately realized how the existence of that link could be tested, and it was then that I came in contact with Trond Torsvik in Norway, who proved to be uniquely qualified to carry out the required tests."

Torsvik, a professor at the University of Oslo in Norway, and Burke developed the conceptual ideas for this research. Additional members of the team were Bernhard Steinberger at the Helmholtz Centre Potsdam in Germany, and Lew Ashwal and Sue Webb from the University of the Witwatersrand in South Africa. The research consisted of applying and interpreting the results of mathematical analysis, much of it applying spherical geometry to the Earth's surface, to publicly available data-sets put together mainly by Ashwal, Webb and Torsvik.

The present structure of the Earth's mantle has been increasingly understood by researchers in seismology during the past 25 years, and Burke and his colleagues' work has helped confirm the seismologists' results. The work of the Burke group, however, also describes the structure as it was in the past, revealing the history of deep mantle structure over the geologically long period of 500 million years. That, Burke said, is new.

"Establishing the history of deep mantle structure has shown, unexpectedly, that two large volumes lying just above the core/mantle boundary have been stable in their present positions for the past 500 million years," he said. "The reason this result was not expected is that those of us who study the Earth's deep interior have assumed that, although the deep mantle is solid, the material making it up would all be in motion all the time, because the deep mantle is so hot and under such high pressure from the weight of rock above it."

As for how this improves the odds of finding these precious gems, Burke explained that geologists interested in diamonds have known for more than 50 years that rare diamond-bearing kimberlite volcanic rocks are highly concentrated in ancient cratons within areas of the Earth's continents. This has concentrated the search for diamond-bearing rocks within an area amounting to no more than about 10 percent of the entire area of the world's continents. The new work has shown that most of the kimberlites have been erupted into one or the other of those old cratons only under certain conditions. These findings will enable the search for to be further concentrated.

Ultimately aiming for a better integrated understanding of how the solid Earth of the crust and mantle works, the group hopes to obtain further results within months. They hope to better establish how plate motions at the Earth's surface have evolved over the last 500 million years and how to work out just how those movements have related to both the stable and the moving parts of the Earth's mantle during the same interval.

Explore further: Puget Sound quake likely in Seattle Fault zone, geologists say

Related Stories

The Earth's hidden weakness

May 28, 2010

(PhysOrg.com) -- Three thousand kilometres beneath our feet, the Earth's solid rock gives way to the swirling liquid iron of the outer core.

The continents as a heat blanket

Jan 22, 2009

Drifting of the large tectonic plates and the superimposed continents is not only powered by the heat-driven convection processes in the Earth's mantle, but rather retroacts on this internal driving processes. In doing so, ...

Recommended for you

Study links changing winds to warming in Pacific

Sep 22, 2014

A new study released Monday found that warming temperatures in Pacific Ocean waters off the coast of North America over the past century closely followed natural changes in the wind, not increases in greenhouse ...

User comments : 7

Adjust slider to filter visible comments by rank

Display comments: newest first

omatumr
1 / 5 (2) Jul 14, 2010
Diamonds in meteorites contain a tracer isotope that tells us where to look for more diamonds.

The tracer isotope is excess Xe-136, enriched to about twice its normal value [Nature 277 (1979) 615-620].

The Galileo Mission to Jupiter discovered this same tracer isotope, excess Xe-136, in Jupiter [Meteoritics and Planetary Science 33, A97 (1998) paper 5011].

But if Jupiter contains tons of diamonds, the price of diamonds will drop and they will become about as valuable as a ton of sand.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
barakn
1 / 5 (1) Jul 14, 2010
If Jupiter contains tons of diamonds they will remain there forever due to the impossibility of retrieving them from such immense pressures and temperatures up through such an immense gravity well. This inability to think about the physics of astronomical objects explains why you are a FORMER NASA PI.
trekgeek1
not rated yet Jul 14, 2010
Can't we just make the damn things for the same cost? The wiki article says that they can be inferior or superior depending on the quality. This sounds like the real stuff to me. Choose how big and perfect you want it and let them make one.

The article also mentions devices to decipher between real and synthetic, though I find it amusing that you'd have it tested to find out that your real diamond is inferior and thus more valuable.
gunslingor1
1 / 5 (1) Jul 15, 2010
Diamonds are rediculously overvalued. They can easily be made in a lab. Most of the apparatices are being kept quite, for the last 50 years, by companies like Zales and da Bears! But on the other hand, most of the patents for these devices have expired. I intend to make my wife a diamond someday, not buy one.

omatumr
1 / 5 (2) Jul 15, 2010
In today's issue (15 July 2010) of Physics World is a related news report "Geologists map likely location of diamonds".

There the ultimate source of diamonds is better explained and referenced:

Primordial diamonds in primitive meteorites, the ultimate source, contain a tracer isotope - excess Xe-136 from the r-process of stellar element synthesis [Meteoritics & Planetary Sciences 29 (1994) 791 and 811; Geochimica et Cosmochimica Acta 59 (1995) 115].

The Galileo Mission found this same tracer isotope in the atmosphere of Jupiter, a massive planet with sufficient internal pressure and temperature to produce diamonds [Meteoritics & Planetary Science 33 (1998) A97, paper 5011].

Jupiter contains abundant carbon - the element that forms diamonds - and may contain high abundances of diamonds and actinide elements like Th, U and Pu. These heavy elements were made in the r-process of stellar element synthesis and continue to generate heat in planets today by spontaneous nuclear decay.
Husky
not rated yet Jul 15, 2010
in a cynical way the vice grip of the Beers monopoly may have prevented WW3 from ever happening as their control extended both in the soviet union and the USA, da beers wouldn't want to let the cold war heat up any further than have USA vs CCCP sponsored tribal wars in africa during the 70's 80's to keep diamond pricve high
Shootist
not rated yet Jul 17, 2010
Interesting however the DeBeers mines in SA are right in the middle of the largest known impact crater on the planet. The second largest impact crater (Sudbury) on the planet is also its richest nickel deposit.

Coincidence? No. Vredfort would have generated a mantle plume, as would Sudbury. Too bad that badly named dinosaur crater, Chicxulub, hit limestone, nothing there of worth.