Showing posts with label mantle. Show all posts
Showing posts with label mantle. Show all posts

Thursday, January 12, 2017

Big Diamonds From Great Depths and how do Gemstones Form: The most valuable jewelry offers researchers important information from the depths of the Earth

Geologists studied these scraps of diamond leftover from the shaping of big jewels. Evan Smith/Gemological Institute of America
Evan Smith wanted to get his hands on the world's biggest diamonds — the kind that sit at royal scepters, and the ones that are always the target of elaborate movie heists.

But this wasn't for some nefarious get-rich-quick scheme. It was for science.

"The most valuable, the most prized, of all gemstones are coincidentally some of the most scientifically valuable pieces of the Earth," says Smith, a diamond geologist at the Gemological Institute of America.


The Ungraspable Value of the World's Largest Diamond The New Yorker

They're scientifically valuable because they come from a deep part of the Earth that humans can't access and don't know that much about.




GEMSTONE TREASURES OF THE WORLD POSTER  Jewelry auction Pinterest

Because of their rare size and quality, Smith thought these diamonds might have come from somewhere different, though no one knew exactly where.

"It was a total mystery," says Smith.


Layers of the Earth - Maggie's Science Connection

To solve that mystery, he'd have to look inside the diamonds, at tiny specs of junk no wider than a human hair that the crystals had brought with them on their journey from the deep.


"You really couldn't ask for a better vessel to store something in. Diamond is the ultimate Tupperware," says Smith.


World's Largest Rough Diamond Fails to Sell At Auction Forbes

A slogan like "the ultimate Tupperware" won't sell many engagement rings, but for scientists, the diamonds' Tupperware-quality is key. It makes the geologic equivalent of messages in a bottle.


But Smith couldn't just knock on a royal palace door and ask to crack open the crown jewels.


Price and Buying Guide for 4 Carat Diamonds

Evan Smith

Gemological Institute of America

Instead, he got the Gemological Institute of America to buy eight fingernail-sized chunks of those big diamonds, the scraps leftover from when the rough diamonds were cut into sparkly jewels.


Earth structure infographic Freepik

After grinding some down and cutting others open, Smith used fancy techniques involving big microscopes, lasers and electron beams to figure what was inside. He also used some not-so-fancy equipment — a magnet attached to a string — to figure out if they contained iron. ("After staring at these inclusions for hours on end over the course of many months, you start to resort to some alternative tools," he says).



Diamond Cutting Green Laser Machine Diamond Industry

Smith eventually found that many of the stones contained bits of garnet with a silicon content indicating that they must have formed under very high pressure. He also found iron and nickel, shrouded in invisible envelopes of fluid methane.

"That's unusual. This is the first time I've seen methane around an inclusion," he says.


When he took a nondestructive look at 53 other diamonds passing through the institute for quality grading, he found that 38 of them contained the same unusual materials.

As Smith and his colleagues wrote Thursday in the journal Science, those odd bits and pieces told him two important things.


How Do Gemstones Form? Gem Rock Auctions

"One, they tell us that these large, exceptional-quality diamonds originate from extreme depths in the Earth," he says, from about 200 to 500 miles below us.


That's about as far under our feet as the International Space Station is above our heads. And it's about twice as deep as where most diamonds are born.

"So, that in itself is pretty amazing," says Smith.


The second thing he learned is that the diamonds had formed inside oxygen-deprived patches of liquid metal. And that's the first hard evidence that the Earth's mantle is not a uniform stew of oxygen-rich rocks



World's First Realization of Ultrahigh Pressure and Ultrahigh Temperature at the Earth's Center - Finally reaching the Earth's Core — SPring-8 Web Site

It might not sound very exciting, says Kanani Lee, a mineral physicist at Yale University, but it is.

"It further complicates things, but it makes us have to think more deeply about what's going on in the planet because ultimately this does affect what we see up on the surface," says Lee.

As the Earth cooled over the last 4.5 billion years, its layers slowly revolved from the core to the surface and back again. Until recently, scientists expected that the mantle, the part of the planet between the continental plates and its core, would be pretty thoroughly mixed, with oxygen distributed throughout. But these diamonds show that until relatively recently, there were pockets that somehow managed to resist that mixing.


A rare diamond carried this tiny package of material from hundreds of miles underground. It's about as wide as a poppy seed. Evan Smith/Gemological Institute of America


And those pockets were long-lasting and widespread enough to produce diamonds that surfaced on multiple continents and that range in age from about 100 million years old to about a billion years old.

It's unclear if those pockets are still around now. Nevertheless, it means that the planet and its past could be a little messier than scientists first thought.

"It tells you that we have to refine our thinking about how the planet – whether it's Earth or any other planet — evolves with time. And that our simple pictures may not be good enough anymore if we can't explain these features," says Lee.

Those odd features are just slivers of a much larger picture — how Earth became what it is today, including its ability to host life.


"Over time, those are the things that shape the surface of the Earth. They're the materials that the whole surface of the Earth is built with," Smith says.



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The above post is reprinted from materials provided by Npr. Note: Materials may be edited for content and length.

Monday, December 26, 2016

Earth's mantle cools more quickly than was previously thought

Oceanic crust newly formed thinner than the old one, according to research. This indicates that the shell thinning earth cooled more quickly than was previously supposed

Studies have shown that the thickness of the newly volcanic crust has thinned over the last 170 million years. At a symposium of the American Geophysical Union, the researchers noted that this newly formed crust cooled two times faster than was previously thought.

From Earth's deep mantle, scientists find a new way volcanoes form Phys.org

This process provides valuable information about how the tectonic plates moderates internal temperature of the planet, according to Harm Van Avendonk, co-author of the study and a geophysicist at the University of Texas at Austin.

The discovery is fascinating, although more information is missing because oceanic crust thickness measurement requires seisimice studies. It also may explain why such supercontinents Pangea broke.

The upwelling of material deep in Earth's mantle can produce Earth.com

The shell is made up of rock earth hot (500-900 ° C at the top), under high pressure. When this material rises to the earth's surface, the pressure drops and rock begins to melt. This material may ascend to the surface by ocean rifts and build new crust. When the jacket temperature is higher, thicker crust is formed.

Comparing now the crust of 170 million years ago it was noticed that the old one is thicker by 1.7 km. The chemical analysis shows the lava rocks in that the mat formed was cooled to 6-11 degrees per 100 million years in the past 2.5 billion years. But the average Jurassic (170 mil. Years), mantle cooled by an average of 15-20 degrees Celsius per 100 million years.

The Structure of the Earth Marcellus Community Science e-education.psu.edu


Researchers have hypothesized that the tectonic plates causes this cooling. By forming new crust and sinking tectonic plates, coat loses heat. It has been found that the mantle beneath the Pacific Ocean (area with little tectonic activity) was cooled to 13 degrees Celsius per 100 million years, and the sheath in the Atlantic was cooled to 37 ° C per 100 million years.

An important factor in temperature variation of the shell is the supercontinent. Atlantic and Indian Ocean have occurred due to breakage Pangaea. Before this process, the mantle underneath has been able to keep high temperature, due to the high thickness of continental crust. When breaking, ocean crust mantle beneath the newly cooled quickly, while lowering the temperature of the mantle beneath the Pacific Ocean remained constant.

Earth - The outer shell Britannica

Also, the accumulation of heat beneath the continental crust (as if Pangaea) in a long time, breaking them. Laurent Montesi, a scientist at the University of Maryland, says that "this may explain why a continent breaks after 100 million years."

Facts About Pangaea the Most Recent Supercontinent Geology In



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The above post is reprinted from materials provided by  Science News . Note: Materials may be edited for content and length.